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Protoperithecial differentiation in Neurospora tetrasperma proceeds in four clearly discernible stages: ascogonial bud, ascogonial hook, ascogonial coil, and protoperithecium. This morphogenetic sequence was completely but transitorily blocked at 37°C. Under low oxygen tensions or in the absence of carbon dioxide, only ascogonial coils were differentiated. Glycolytic inhibitors such as 2-deoxy-D-glucose interfered with the ascogonial differentiation. Citric acid cycle inhibitors such as fluoroacetate selectively blocked the further development of ascogonial coils into protoperithecia. Differentiating cultures at 25°C responded positively to external sucrose with respiratory quotients above 1.0, whereas non-differentiating cultures at 37°C, although respiring at high rates, never reached RQ 1.0. These results indicate that carbohydrate metabolism via fermentative glycolysis functions normally in ascogonia differentiating (25°C) cultures only. Comparative chemical analysis showed delayed RNA synthesis, sharp disturbances in protein biosynthesis and metabolism, and lower levels of carbohydrate and bound lipids in young cultures at 37° C. Polyols, especially ribitol and xylitol utilized as sole source of carbon, induced abundant protoperithecial morphogenesis at 37°C. This alleviating effect of polyols were negated by the addition of sugars at 37°C and shown to be a specific metabolic effect. [ABSTRACT FROM AUTHOR]

The ATP levels in photophosphorylation, glycolysis and oxidative phosphorylation, in the unicellular green alga Scenedesmus obtusiusculus, were titrated with narrow concentration intervals of desaspidin in the presence of different concentrations of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), which allows the differentiation between non-cyclic, pseudocyclic and true cyclic photophosphorylation. The data on photophosphorylative ATP levels were compared with earlier data on total binding of phosphate. In the true cyclic process, both parameters are equally sensitive towards desaspidin. Under pseudocyclic conditions and in non-cyclic photophosphorylation, the level of ATP is more sensitive towards desaspidin than is total binding of phosphate. This suggests a structural difference between the cyclic and the two non-cyclic (one of which is also pseudocyclic) sites. The non-cyclic ATP level is more sensitive towards desaspidin than is pseudocyclic. This may be connected with the higher ATP level under pseudocyclic as compared to non-cyclic conditions. [ABSTRACT FROM AUTHOR]

The regulation of glycolysis by phosphofructokinase (PFK) was studied in psoriatic epidermis by measuring the acute changes in the levels of adenosine triphosphate. glucose-6-phosphate plus fructose-6-phosphate, fructose-1 ,6-diphosphate, and lactate after periods of ischemia. In all experiments, acute ischemia caused decreases in the levels of adenosine triphosphate, glucose, and glucuse-6-phosphate plus fructose-6-phosphate, and increases in the levels of fructose-1 ,6-diphosphate and lactate. The rapid depletion of glycolytic intermediates before PFK and the accumulation of those after the enzyme indicate activation of the enzyme by ischemia in psoriatic epidermis. [ABSTRACT FROM AUTHOR]

Purified phosphofructokinase from bakers yeast is activated by d-fructose in low concentrations (up to 1 mM) and inhibited by high concentrations. The stimulatory effect of d-fructose is similar, but smaller than that of AMP. In the presence of AMP (0.4 mM or higher) d-fructose does no longer stimulate, but its inhibitory effect persists ( K=8 mM). Its dualistic action on phosphofructokinase activity indicates that d-fructose might induce low frequency in glycolytic oscillations by direct interaction with the enzyme. [ABSTRACT FROM AUTHOR]

A non-recirculating, haemoglobin-free perfusion system was used to evaluate glycolysis in livers from fasted rats. Glycolysis was calculated from lactate and pyruvate production before and after infusion of glucose. In the absence of extracellular glucose glycolysis was small. Stimulation of glycolytic flux occured at extracellular glucose concentrations above 5 mM. Rates were proportional to glucose concentrations. Glycolysis was also investigated in the presence of extracellular lactate, which is a precursor of gluconeogenesis. High glucose concentrations (15-35 mM) were followed by lactate and pyruvate output suggesting that glycolysis was prevailing. Estimated flux rates, however, were significantly lower in the presence of the gluconeogenic precursor. Our results provide arguments that gluconeogenesis and glycolysis interact in order to regulate the peripheral glucose concentration. [ABSTRACT FROM AUTHOR]

The possibility that free fatty acids (FFA) and their CoA esters may directly inhibit the activity of enzymes of glycolysis and lipogenesis was studied in liver and adipose tissue of acutely diabetic rats. Despite a marked elevation in tissue FFA, the activity of glucose-6phosphate dehydrogenase, phosphofructokinase, pyruvate kinase, α-glycerophosphate dehydrogenase, aldolase, citrate synthetase, and several other enzymes was not affected 3 or 6 h after anti-insulin serum injection. The activities of hepatic and adipose tissue acetyl-CoA carboxylase, hepatic glucokinase and adipose tissue hexokinase were decreased. The tissue FFA levels were compared to linoleate concentrations required for halfmaximal inhibition (Ki) of several enzymes in tissue fractions after in vitro contact of 30 min at 37 °C. Linoleate irreversibly inactivated the enzymes to a varying degree but its effect was dependent on the protein content of the system. The K of linoleate increased linearly with cellular protein concentration; when extrapolated to the protein level in the intact cell it became unphysiologically high, markedly exceeding the liver or adipose tissue FFA concentration of acutely diabetic rats. The K linoleate and the actual FFA concentrations were particularly discrepant in the cytoplasmic compartment, comprising roost of the investigated enzymes, but only a small proportion of tissue FFA, as determined by measurements of intracellular FFA distribution. Similar discrepancy was found for the interaction of palmityl-CoA with glucose-6-phosphate dehydrogenase and acetyl-CoA carboxylase. Thus, the selective decrease in the activity of glucokinase and acetyl-CoA carboxylase in acute diabetes was attributed to factors other than FFA or their CoA esters. The nature of FFA-enzyme interaction, causing enzyme inactivation rather than specific inhibition is discussed, concluding that FFA do not act as direct homeostatic modifiers of enzymes regulating carbohydrate and fat metabolism. [ABSTRACT FROM AUTHOR]

The article discusses the cerebrospinal fluid and monoamine and glucolytic metabolites in Alzheimer's disease. Determinations of acid monoamine metabolites in cerebrospinal fluid (CSF) give valid information on the metabolism of the corresponding amines in the brain tissue. The monoamine metabolites in the CSF are related to age. The concentration of homovanillic acid (HVA) increases with age. Studies of CSF from patients with presenile and senile dementia have shown lower concentration of HVA. Brain hypoxia on the cellular level can be demonstrated by secondary changes in glucose metabolism.

The most noticeable biochemical abnormality of red cells of patients with autoimmune haemolytic anaemia with warm autoantibodies is the increased osmotic fragility of the red cells. This appeared to be most pronounced in patients with incomplete IgG warm autoantibodies and to be significantly correlated with the 51CR T½ of the patients' red cells. It appeared to be a disturbance of - the cells which slowly increased with time. It only occurs in vivo and the reaction of the cell with the autoantibodies is necessary. Possibly, it is caused by damage done to the sensitized red cells by the RES. It is accompanied by an increased K+ efflux of the red cells. Interaction of red cells and antibody in vitro has no effect. A number of other biochemical abnormalities, such as increased enzyme activities, increased glycolysis and ATP breakdown, also correlated with the 51Cr T½ are probably the result of the lower mean cell age of the red cells. [ABSTRACT FROM AUTHOR]

A mathematical model of glycolysis in the steady state of human erythrocytes is proposed based on an analytical treatment. Assuming a linear dependence of the enzyme velocities on the substrate concentrations, which is justified for all non-equilibrium enzymes, simple analytical expressions for all metabolites of the glycolysis could be obtained. From a consideration of the NADH/NAD-coupling between the lactate dehydrogenase and the glyceraldehyde-phosphate dehydrogenase reactions a conservation quantity for the concentrations of the oxidized metabolites is derived. The glycolytic flux was shown to be controlled only by the hexokinase and phosphofructokinase. The control strengths for the hexokinase and phosphofructokinase were calculated to be 0.69-0.73 and 0.31-0.27 at pH 7.2 and 0.87-0.9 and 0.13--0.1 at pH 8.2, respectively for various experimental conditions. The metabolites glucose 6-phosphate and fructose 6-phosphate are only influenced by the characteristic times of the hexokinase and phosphofructokinase. All other metabolites and the NADH/NAD ratio depend additionally on the characteristic time the pyruvate kinase. The level of 2,3-bisphosphoglycerate is influenced furthermore by the characteristic time of the bisphosphoglycerate mutase and by the capacity of the 2,,3'-bisphosphoglycerate phosphatase. The effects of changes in the kinetic properties of enzymes on the concentrations of metabolites may be expressed in form of a control matrix. The enzymes which interact with an outer effector may be identified by means of three guide parameters. The best combination is based on the determination of changes of glucose 6-phosphate, phosphoenol pyruvate and the total flux. This method is much to be preferred to the usual interpretation of crossover-plots. It is shown that pseudo-crossovers occuring at the glyceraldehyde-phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase are not indicative for an interaction site with an effeetor. The model was tested in a number of experimental conditions including variation of the pH, P1 concentration, NH4+-ion concentration and temperature for which crossovers have been described. It explains quantitatively the complicated pattern of changes. The conclusions on the properties of the enzymes drawn from the metabolite concentrations arc, consistent with their behaviour under isolated conditions. It is further shown that under conditions in vitro with lactate accumulation the levels of fructose bisphosphate, triosephosphate and the NADH/NAD ratio are time-dependent. [ABSTRACT FROM AUTHOR]

Dephosphophosphorylase was isolated from swine kidney by a procedure involving precipitation with acetone and ethanol in the presence of glycogen, ammonium sulfate fractionation and chromatography on DEAE-cellulose. The enzyme was purified about 15000-fold to a final specific activity of 30 μmol glucose-1-phosphate formed from glycogen and inorganic phosphate per rain per mg protein at 26°C. Yields of 2O% of the activity present in crude extracts wore obtained by this method. The purified enzyme could be completely converted to a phosphorylated form by incubation with ATP, magnesium ion and a partially purified soluble protein kinase which was isolated from the same crude kidney extracts. The final specific activity of phosphophosphorylase isolated by the same procedure was about 70 μmol glucose-1-phosphate formed from glycogen and inorganic phosphate per min per mg protein at 26°C. Ultracentrifugation and polyacrylamide-gel electrophoresis studies with the purified enzymes indicated that the preparations were homogeneous. Molecular weight determination by Sephadex G-200 and Sepharose 6-B column chromatography revealed V0/Ve ratios which corresponded to a molecular weight of 190000 ± 5000 for both of the enzyme preparations. Sucrose-density centrifugation further confirmed that both forms of kidney phosphorylase had similar molecular weights of about 190000 ± 10000 and s20,w values of from 8.1 to 8.3 S The s20,w values obtained in ultracentrifugation studies, 8.3 to 8.4 S, agreed reasonably well with those obtained by sucrose density centrifugation. The molecular weights of the two forms of the enzyme calculated from this data and a diffusion coefficient of 0.4 μm2/s which was determined by exclusion chromatography and a partial specific volume of 0.735 cm3/g was 195000 ± 5000 in each ease. When the enzymes were subjected to polyacrylamide-gel electrophoresis in the presence of sodium dodecylsulfate a single sharp protein band was observed. These studies showed that both forms of the enzyme contained two identical subunits with molecular weights of 95000. Some of the kinetic and allosteric properties of the phospho and dephospho-forms of purified kidney phosphorylase were examined and compared. The Km of the phosphorylated form of the enzyme for Pi was 2.8 mM compared to 100 mM for the dephospho-form in the presence of 0.2 mg glycogen and 2 mM AMP. The corresponding values for glycogen at about 4 mM Pi were 1.4 mM and 20 mM for the phospho and dephospho-forms, respectively. The apparent Km values for Pi or glycogen varied as a function of the other substrate for the dephospho-enzymo. This effect was not observed with the phospho-enzyme. The dephospho-form of kidney phosphorylaes required AMP for activity and protamine also stimulated the activity of this form of the enzyme. Glucose (0.5 mM) inhibited the activity of kidney dephosphophosphory]ase. A protein kinase isolated from crude kidney extracts converted the dephospho-form of the enzyme to a phosphorylated form in the presence of ATP and magnesium. About two equivalents of phosphate were transferred from ATP to the phosphorylated form of the enzyme during this conversion. [ABSTRACT FROM AUTHOR]

The intracellular distribution of ATP, 2,3-bisphosphoglycerate(P2-glycerate) and Mg2+ was calculated for the oxygenated and deoxygenated human erythrocyte for the normal range and that of pathophysiological variations based on the association constants of the relevant complexes. The data indicate that about 20% of ATP is bound both in the oxygenated and deoxygenated cells, while 39 and 73% of P2-glycerate is bound under these conditions. An increase of the free Mg2+ concentration from 0.7 to 1.1 mM is produced by complete deoxygenation of haemoglobin. The calculations would indicate that during deoxygenation of haemoglobin the hexokinase reacts to the increased concentration of the activator Mg2+ and the decline of the inhibitor P2-glycerate with an elevation of its activity which corresponds to experimental data on intact erythrocytes. The P2-glycerate formation rate in deoxygenated cells is stimulated about 2.5 times in comparison to oxygenated cells as estimated from the free concentration of P2.glycerate and the kinetic constants of bisphosphoglycerate mutase. An assessment of the possible influence of other anions including bicarbonate shows that the distribution of the species of ATP, P2-glycerate and Mg2+ are changed by less than 20%. Together with the data presented in the accompanying paper, the results given here indicate that the constants and estimates are approximately valid for intracellular conditions. [ABSTRACT FROM AUTHOR]

Pure and viable human granulocytes were prepared from peripheral blood, and incubated in a buffered saline medium. Glycolytic intermediates, adenine-nucleotides, glycogen, glucose and oxygen consumptions, and lactate production were measured under standard (aerobiosis, pH 7.4) and modified conditions. Standard incubations allow the determination of mass-action ratios, which localize regulatory steps at hexokinase, phosphofructokinase and glyceraldehydephosphate dehydrogenase : phosphoglycerate kinase. Anaerobiosis results in an increased glucose consumption while lactate production remains normal, presumably because of an increased glycerolipid synthesis induced by the elevated NADH/NAD+ ratio. A positive crossover at phosphofructokinase level derives from ATP diminished content. 0.5 mM 2,4-dinitrophenol induces an increased oxygen consumption, an ATP fall and a positive crossover at phosphofructokinase level with an augmented overall glycolysis, pH-changes modify phosphofructokinase activity, as revealed by the positive and negative cross-overs respectively observed at pH 7.80 and 6.85. 0.1 mM and 0.2 mM monoiodacetate inhibits overall glycolysis without increasing oxygen consumption; the NAD+/NADH ratio is notably decreased; an apparent positive crossover again appears at the phosphofructokinase step, but the decreased hexose-monophosphate level may result from the diminished ATP, whose concentration is not far from the Michaelis constant of hexokinase. 2 mM to 20 mM sodium fluoride protects glycogen, inhibits glycolysis and dramatically increases oxygen consumption. 0.2 mM to 0.5 mM NaF-activates glycolysis and glycogen breakdown, and inhibits oxygen consumption. 3 mM dibutyryl adenosine 3′:5′-monophosphate increases glycogenolysis and induces two cross-overs: a positive one at phosphofructokinase and a negative one at glyceraldehyde-phosphate-dehydrogenase : phosphoglycerate kinase level. The lipolytic action of 3′:5′-AMP may explain those effects, by decreasing ATP/ADP and NAD+/NADH ratios. A comparison between over-all glycolytic activities and cross-over plots clearly indicates that granulocyte glycolysis is regulated at the hexokinase step by ATP availability as compared with Michaelis constant, at the phosphofructokinase level through an allosteric ATP inhibition, and at the glyceraldehyde-phosphate-dehydrogenase step by mass-action of the NAD+/NADH ratio. [ABSTRACT FROM AUTHOR]

Because of differences in the pattern of enzyme activities involved in glycolysis and gluconeogenesis between rat and guinea pig liver, the regulation of gluconeogenesis in guinea pig liver was studied. The following results were obtained: 1. Starvation increases the capacity for gluconeogenesis from pyruvate in vivo. 2. Gluconeogenesis from L-lactate and from pyruvate in isolated perfused livers is greater in the guinea pig than in the rat, whereas gluconeogenesis from other precursors is similar in both species. 3. Long chain and medium chain fatty acids inhibit gluconeogenesis from L-lactate in isolated perfused guinea, pig liver but stimulate gluconeogenesis from L-lactate in isolated perfused rat liver. In the guinea pig liver the difference does not result from a lower rate fatty acid oxidation but from a greater reduction in the cytoplasmic NAD+/NADH system. During enhanced fatty acid oxidation in guinea pig liver and in rat liver, similar changes in the concentrations of both acetyl-S-CoA and CoA-SH are observed. With high concentrations of pyruvate as the gluconeogenic precursor, both fatty acids and ethanol lead to a slight stimulation of glucose formation formation by supplying hydrogen equivalents to the cytosolic NAD+/NADH system. 1. Both glucagons and dibutyryl-Ado-3': 5'-P stimulate ureogenesis and ketogenesis in isolated perfused guinea pig liver. However, the stimulation of gluconeogensis by glucagons and Ado 3': 5'-P normally observed in isolated perfused rat livers was not found in isolated perfused guinea pig livers. 2. Partially purified pyruvate carboxylases from rat and guinea pig liver do not differ with respect to the apparent Km values for pyruvate and ATP, and also the apparent Ka values for acetyl-S-CoA at different pH values. At constant concentrations of MgATP2- or MnATP2- the pH-optima for the guinea pig enzyme are significantly lower. 5. 5-Methoxyindole-2-carbonic acid inhibits gluconeogenesis in guinea pig liver in the same way as in rat liver. Quinolinate, on the other hand is far less inhibitory in guinea pig liver and does not inhibit at all in isolated perfused pigeon livers. 7. Major species differences are found when the activities of the rate limiting enzymes involved in gluconeogenesis are measured under Vmax conditions. Pyruvate carboxylase activity is in the same range rat and guinea pig liver; pyruvate kinase activity is considerably lower, phosphoenolpyruvate carboxykinase activity is considerably higher in guinea pig liver. According to our results gluconeogenesis in guinea pig liver from lactate or pyruvate is mainly regulated by the concentration of pyruvate. The difference in the regulation of gluconeogenesis between rat and guinea pig liver probably results from a difference in the compartmentalization of phosphoenolpyruvate carboxykinase. A higher rate of futile cycling between phosphoenolpyruvate and pyruvate in rat liver, due to the higher activity of pyruvate kinase in relation to the activities of phosphoenolpyruvate carboxykinase and pyruvate carboxylase, may also contribute to the observed differences. [ABSTRACT FROM AUTHOR]

Rat parotid gland slices showed a very slow rate of glucose utilization and lactic acid production, both in the presence and in the absence of oxygen. Epinephrine, which caused rapid enzyme secretion by the slices did not affect the low rate of glycolysis. A rough calculation indicates that in the parotid gland ATP is produced by oxidative phosphorylation 50 times faster than by glycolysis. The mitochondria, when isolated and tested in presence of EDTA or EGTA showed respiratory activity and respiratory control comparable to those of liver mitochondria. Adenosine 3':5'-cyclic phosphate, which is an intermediate in induction of enzyme secretion, showed no clear-cut effect on the functions of the parotid mitochondria. Isolation of the mitochondria in the absence of the above chelators yielded a preparation which was almost depleted of NAD, respired feebly on NAD linked substrates and showed no respiratory control. Addition of NAD+ restored respiration. The damage caused to these mitochondria during isolation was attributed to the high calcium concentrations found in the gland. Addition of small amounts of free calcium to functional parotid mitochondria indeed caused the loss of NAD and the decline of respiration. Tested in parallel experiments, liver mitochondria were much more resistant to added calcium. Their initial calcium content was one tenth that of the parotid mitochondria. The control of calcium distribution in the parotid gland and the possible functions of calcium are discussed. [ABSTRACT FROM AUTHOR]

Certain kinetic properties of the pyruvate kinase activity in different tissues of the rat have been studied in fresh extracts with particular attention to their possible value for the regulation of gluconeogenesis and glycolysis. The pyruvate kinase activity in fresh extracts of the gluconeogenic tissues liver and kidney cortex has allosteric properties very marked m near physiological conditions, as follows: (a) cooperativity in the kinetics with respect to the concentration of phosphoenolpyruvate; (b) strong allosteric inhibition by alanine and ATP, each of which raises the [S]0.5 value and increases the sigmoidicity respect to the concentration of phosphoenolpyruvate; and (c) very strong activation by fructose diphosphate, which greatly lowers the [S]0.5 value and shifts the kinetics from markedly sigmoid to hyperbolic, and can fully counteract the inhibitory effects of alanine and ATP. Keeping the extracts of liver and kidney at low temperature (0-2°) leads to desensitization of the pyruvate kinase to the homotropic cooperativity of the phosphoenolpyruvate substrate and to the allosteric inhibition by alanine and ATP and the activation by fructose diphosphate. This cold desensitization is reversible. These facts and their time dependence make it possible to understand previous difficulties to obtain reproducible allosteric effects with the pyruvate kinase of rat liver. The pyruvate kinase of other tissues examined, including heart and adipose tissue, did not exhibit any of the allosteric properties above described for the enzyme of the gluconeogenic tissues. The μmolar range of fructose diphosphate concentrations required for activation of liver pyruvate kinase in the presence of the two physiological inhibitors and within the physiological range of concentrations of phosphoenolpyruvate fits well m order of magnitude with the calculated range of concentrations of free fructose diphosphate prevailing in liver. These results strongly support the hypothesis that an isoenzyme of pyruvate kinase present liver and kidney has evolved with built-in specific regulatory mechanisms m order to prevent the diversion of phosphoenolpyruvate from its way to glucose in gluconeogenic situations. An efficient regulation in the reversible switch over from glycolysis to gluconeogenesis seems to be feasible by the interplay of two feedback inhibitors, alanine and ATP, and a forward activator, fructose diphosphate. [ABSTRACT FROM AUTHOR]

Diets rich in fructose, glycerol, or both were fed to normal and diabetic rats, and the activities of enzymes which catalyze irreversible steps of glycolysis and gluconeogenesis were studied in liver. With these diets, rich in precursors of triosephosphates, the activities of glucose-6-phos- phatase and pyruvate kinase in liver were high, while those of glucokinase and phosphoenol-pyruvate carboxykinase were low. A metabolic bifurcation to glycolysis and gluconeogenesis, below and above the triosephosphates level respectively, has then been shown to be easily maintained in liver. It is suggested that the induction of glucokinase and pyruvate kinase in diabetic animals after insulin administration is a sequential process that involves hormonal induction of gluco-kinase by insulin and secondary metabolite induction of the L isoenzyme of pyruvate kinase by some glycolytic intermediate. The occurrence of independent mechanisms for the regulation in liver of the activity of enzymes which catalyze irreversible steps of glycolysis and gluconeogenesis affords a valuable metabolic plasticity. [ABSTRACT FROM AUTHOR]

Experimental procedures and conditions are described for the determination of specific radio-activities of 16 different P-positions in 12 phosphorylated liver compounds after labelling in vivo with [32P]orthophosphate. These data are necessary for calculations of flux rates within the mononucleotides and the glycolytic pathway. Purification procedures for the following compounds are given: ATP, ADP, GTP, UTP, UDPG, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-biphosphate, dihydroxyacetonephosphate, glycerol 3-phosphate, phosphoglyceric acid and phosphoenolpyruvate. The purification of each compound consists of 3–5 chromatogaphic steps, in most eases including a specific enzymic conversion. A preparation procedure is described for mouse liver which shows only a negligible artificial isotope exchange between the β- and γ-P-positions of ATP. This was proved by addition of labelled ATP to non­labelled livers. Five and ten min after intravenous injection of carrier-free [32P]orthophosphate the specific radioactivities of the compounds examined show identical values, thereby excluding compartmentations with isotope kinetic relevance. [ABSTRACT FROM AUTHOR]

The technique and theoretical implications of an analogue computer processing of tracer data in complex metabolic systems are outlined. The procedure may be used for the prediction and analysis of experimental results. The analysis is carried out in three steps: model construction and mathematical formulation; construction of one particular set of fluxes compatible with the data; generalization to give all compatible flux combinations and to fix restrictions on permissible flux values. Usually, metabolic systems are characterized by a slow input of radioactivity. The resulting numerically ill-conditioned matrices either restrict the extractibility of certain parameters or lead to ambiguous results. Uses and limitations of the procedure are discussed in terms of glycolyric net flow in erythrocytes. In contrast to intuitive conclusions in previous papers, a detailed treatment of the literature data reveals that some 50% of the net flow goes via the biphosphoglycerate shunt. Usually, tracer experiments yield the isotopic shuttle rather than the net flux rate. However, an expression of the shuttle in terms of the free enthalpy or the equilibrium of the reaction may be derived. Thus, absolute flow and net flow are of similar information content for regulation problems. The applicability of flee-energy considerations in vivo may be tested directly with the tracer method. [ABSTRACT FROM AUTHOR]

In the first few minutes of oscillatory controlled glycolysis yeast cells convert 500% of all glucose taken up into ethanol and glycerol, and incorporate 8O-9O% of the rest into some insoluble polyglycoside. Glucose uptake in glycolysing yeast cells is a pulsatory process which is in phase with fructose-1,6-diphosphate synthesis. The concentration of UDPG, an intermediate in polyglucoside synthesis, is oscillating in phase with glucose-6-phosphate. The cells use 80-90% of all ATP synthesized in glycolysis for uptake and storage of glucose. [ABSTRACT FROM AUTHOR]

The paper describes a simple kinetic model of an open monosubstrate enzyme reaction with substrate inhibition and product activation. A comparison between the model and the phosphofructokinase reaction shows a close resemblance between their dynamical properties. This makes it possible to explain qualitatively most experimental data on single-frequency oscillations in glycolysis. A mathematical analysis of the model has shown the following. In the model, at a definite relationship between the parameters, self-oscillations arise. The condition of self-excitation is satisfied more readily with a lower source rate, larger product sink rate constants, lower product-enzyme affinity and higher enzyme activity. Self-oscillations exist only in a certain range of values of the parameter determining the degree of substrate inhibition. This range increases with decreasing source rate. Too strong or, conversely, too weak substrate inhibition leads to damped oscillations. The period of self-oscillations depends on the degree of substrate inhibition, the source rate, the sink rate constant, the enzyme activity, the affinity of the substrate and the product for the enzyme; it decreases with an increase in these values. With an increase in the relative sink rate constant the steady state amplitude of self-oscillations initially increases until a definite maximum is reached and then drops to zero. A self-oscillatory state in the phosphofructokinase reaction exists only when the maximum rate of this reaction is essentially higher than the source rate, and lower than the maximum rate of the reactions controlling the sink of the products. An experimental investigation of self-oscillations in the phosphofructokinase reaction may be considerably simplified by using a reconstituted system consisting of a small number of reactions with an irreversible sink of the products and artificial substrate supply. In this case the above relationship (section 6) should hold. [ABSTRACT FROM AUTHOR]

Levels of glycogen and of glycolytic intermediates were assayed in quickly frozen embryonic mesodermic tissue (decapitated and eviscerated chick embryos) at the 5th and 7th developmental day and in the hind limb musculature in subsequent pre- and post-natal stages. Serial determination of dry weight values during embryonic development allows conversion of the levels which are reported on a wet weight basis. While glycogen gradually increases from the 9th day onwards reaching about 1⁄3 of the adult amount on hatching, no substantial differences between early embryonic and adult levels were noted in the case of other intermediates, such as glucose, dihydroxyacetone-phosphate, glyceraldehyde-3-phosphate, 3- and 2-phosphoglycerate, phosphoenolpyruvate, pyruvate and lactate. Glucose-1-phosphate, fructose-6-phosphate, glucose-6-phosphate and fructose-1 ,6-diphosphate were low during most of the embryonic development, attaining levels close to the adult ones only on hatching. In order to study the flow rates, the equilibrium situation at each single step and the possible control points along the glycolytic pathway, the tissue was stressed by brief periods of ischaemia or by electrical stimulation at different stages of development. Glycolytic flow rates showed a progressive increase up to hatching, where a lactate accumulation of 1.5 μmole/min/g wet weight was measured. The maximum rate of 12.9 μmoles/min/g wet weight found in electrically stimulated muscle of hatching chicks, is well below the adult value of 52.7 μmoles/min/g wet weight. The approximate stoichiometric correspondence between glucose + glycogen breakdown and lactate formation, found to exist in the early and late embryonic stages, is absent on the 7th and incomplete on the 11th day, where the sharply reduced gluco- and glycogenolysis cannot account for the measured glycolytic rate. The existence of a vicarious anomalous glycolysis, supplying pyruvate and lactate by transamination or by other unknown mechanisms, is possible at these two stages. The constancy of mass-action ratios under altered glycolytic fluxes and the comparison between the ratios its in vivo and the thermodynamic equilibria show that phosphoglucomutase, phosphoglucose isomerase, aldolase, triosephosphate isomerase, phosphoglycerate mutase and enolase were maintained either at equilibrium or fairly close to equilibrium. Owing to the probable compartmentation of ATP and ADP in muscle, no calculation of kinase-catalyzed reactions was attempted. Activation of glycolysis could not be observed on electrical stimulation of embryonic muscle at the 14th day, as the constancy of such indicator metabolites as glucose-6-phosphate, fructose-1,6-diphosphate and lactate demonstrates. An activation at the phosphorylase and phosphofructokinase steps has been indirectly shown on hatching. [ABSTRACT FROM AUTHOR]

Narrow concentration intervals were used, covering 10−6– 10−4M desaspidin. The interaction with glycolysis involves three steps, the inhibitor constants (Ki:s) being in turn 2.7 × 10−5M, 1.3 × 10−4M, and high. About 18% of total glycolysis is inhibited in each of the two first steps, and 65% left for the third reaction. After compensation for glycolysis, oxidative phosphorylation may show a sudden jump to about 10% inhibition at 1.5 × 10−5M desaspidin, the possible Ki of the reaction starting here being very high. Correcting for glycolysis, desaspidin affects total Photophosphorylation in two steps, with the Ki values of 7.8 × 10−5M and 4.6 × 10−4M respectively. Inhibition in the first step is about 27% of the total photophosphorylation. By applying 10−6M DCMU[/3‐(3, 4‐dichlorophenyl)‐l, l‐dimethy lurea], one can abolish non‐cyclic photophosphorylation. Desaspidin then reacts in a single step with a Ki of 1.4 × 10−4M. At 5 × 10−5M DCMU, also the pseudocyclic photophosphorylation is abolished. The remaining, true cyclic photophosphorylation has a single Ki of 2.3 × 10−5M for desaspidin. Under non‐cyclic conditions, the true cyclic process contributes about 25% to total Photophosphorylation. Under pseudocyclic conditions, no cyclic photophosphorylation occurs. Under true cyclic conditions, the non‐cyclic and pseudocyclic processes are inoperative. This indicates a regulative system, so that either (1) the (non‐cyclic + true cyclic), (2) only the pseudocyclic, or (3) only the true cyclic systems can be traced, dependent on the level of DCMU applied. There are two sites for non‐cyclic Photophosphorylation, one of them common to the pseudocyclic pathway. Cyclic photophosphorylation has a third site, different from the other two. [ABSTRACT FROM AUTHOR]

The content of adenosine triphosphate (ATP) in roots of wheat (Triticum aestivum L.) was determined with the firefly-luciferase method. The content is decreased by D-mannose, which inhibits root growth, respiration and chloride uptake. In intact seedlings the inhibition of root growth is relieved by other sugars and also by the flavanone naringenin and by 2,4-dinitrophenol. This reversal is combined with an increased content of ATP. The inhibition of chloride uptake by mannose in excised roots is reversed by some other sugars (including D-galactose which is in itself inhibitory to root growth), and also in this case the ATP content is increased. Naringenin and dinitrophenol do not relieve the inhibition of chloride uptake caused by mannose. Nor do they increase the content of ATP in this case. The primary effect of mannose seems to be inhibition of glycolysis whereas the effect upon root growth is secondary. Galactose, which also inhibits root growth, does not inhibit respiration or reduce the ATP content and the primary effect of galactose (and also of 2-deoxy-D-glucose and 2-deoxy-D-galactose) seems to be on the synthesis of cell wall substances. [ABSTRACT FROM AUTHOR]

Phosphofructokinase (PFK) was partially purified (× 50) from rhesus monkey epidermis. Kinetic studies showed a biphasic regulation of this enzyme by ATP, i.e., activation at low concentrations and inhibition at high concentrations. The partially purified PFK was inhibited by ATP at a final concentration well below the physiologic intracellular level. This feedback inhibition was counteracted by cyclic 3',5'-AMP, 5'-AMP, ADP and Pi; moreover Pi plus one of these adenine nucleotides showed marked synergistic effects. Epidermal PFK was also inhibited by citrate and the inhibition was released by cyclic 3',5'-AMP, 5'-AMP, and Pi. The initial velocity of the PFK reaction plotted against a variable substrate (F6P) level yielded a sigmoid curve, characteristic of a regulatory allosteric enzyme (Hill coefficient "n" > 1). This allosteric characteristic was strengthened at higher ATP concentrations and weakened at lower ATP levels. The allosteric nature was lost by the addition of cyclic 3',5'-AMP (i.e., Hill coefficient "n" → 1). These kinetic data indicate that in the rhesus epidermis PFK is a key enzyme that regulates glycolysis. [ABSTRACT FROM AUTHOR]

Oxygen consumption with and without glucose and aerobic and anaerobic lactic acid production have been measured in vitro in skin pieces from different groups of hairless mice, totaling 1051 animals of both sexes. The oxygen consumption showed significant and identical seasonal variations during two consecutive years. Highest values were found in spring and early autumn, while the lowest values were seen in winter and mid-summer. The anaerobic lactic acid production was inverse to the oxygen consumption with lowest values in spring and autumn, indicating that the metabolic variations are actively regulated in the cells. Possible causes of this biphasic pattern are discussed. No diurnal variations were found and region of the body, age or weight did not influence the metabolic parameters. Females had higher respiration and glycolysis than males but lower average weight. [ABSTRACT FROM AUTHOR]

Epidermal slices can produce ATP by both glycolytic and respiratory reactions. Via glycolysis, ATP is produced at a maximal rate of about 0.1 μmole/hr/mg of fresh tissue when slices are incubated in the presence of glucose at concentrations equivalent to normal blood levels. Most of the glucose is converted to lactate, and only a small percentage of the glucose metabolites are oxidized. Respiration generates the majority of the energy for the epidermis, producing ATP at a rate of 0.5 μmole/hr/mg of tissue. The main respiratory reactions of the epidermis in vitro are β-oxidation of lipids and the Krebs cycle. Slices of human epidermis in culture show a relatively constant rate of respiration for several hours in the absence of added substrate, and endogenous components are the main substrates of respiration even in the presence of added nutrients. Cellular phospholipids are probably the major endogenous nutrients for this oxidation. The constant rate of epidermal respiration, the limited oxidation of glucose metabolites, and the Pasteur effect indicate that epidermal energy metabolism is subject to a strong and complex control by biochemical factors. These factors are more prominently expressed in the intact epidermis than in homogenates or extracts. Data are cited which suggest that nucleotide cofactors, particularly ATP, play an important part in energy control by modifying key enzymes of the energy pathways. In light of these data and current concepts of biochemical regulation, an hypothesis is presented in which nucleotides and other intermediates synchronize the rates of glycolysis and respiration, markedly limiting the oxidation of pyruvate by the Krebs cycle. They also may contribute to the accumulation of glycogen, which is observed in wounds and psoriatic epithelium. [ABSTRACT FROM AUTHOR]

Evidence that phosphofructokinase regulates glycolysis in skin and its appendages is presented. The regulation of glycolysis by phosphofructokinase was studied by measuring the acute changes in the levels of adenosine triphosphate, glucose-6-phosphate (plus fructose-6-phosphate) and fructose-1, 6-diphosphate in human hair follicles and rhesus monkey skin, and its appendages after periods of ischemia. In all experiments, acute ischemia caused decreases in the levels of glucose-6-phosphate and adenosine triphosphate and an increase in the level of fructose-1, 6-diphosphate. The rapid depletion and accumulation of the glycolytic intermediates before and after the phosphofructokinase step indicate an acute activation of this enzyme by ischemia. [ABSTRACT FROM AUTHOR]

The hormonal regulation of glycolysis was studied in the costovertebral gland of male hamsters. Castration caused marked atrophy of the gland and reduced its glycolytic rate to one half. Among the glycolytic enzymes, marked decrease in activity occurred only in hexokinase, phosphofructokinase, aldolase, and glyceraldehyde-3-phosphate dehydrogenase; this decrease appeared to be responsible for the reduction in glycolytic rate. The activities of other glycolytic enzymes were little affected by the castration. The activities of glucose-6-phosphate and 6-phosphogluconate dehydrogenases, enzymes of the pentose cycle, decreased markedly after castration. Testosterone caused the atrophied gland in the castrate to become hypertrophic. The over-all rate of glycolysis and the activities of hexokinase, phosphofructokinase and glucose-C-phosphate dehydrogenase returned to their normal values within 1 or 2 weeks after the testosterone treatment, whereas lactate dehydrogenase activities did not change significantly throughout the reactivation process. The testosterone-stimulated increases in hexokinase and phosphofructokinase activities were inhibited by actinomycin D, an inhibitor of DNA-directed RNA synthesis. The results presented here suggest that testosterone actively participates in controlling the structure and function of the sebaceous glands through regulation of protein and nucleic acid synthesis. [ABSTRACT FROM AUTHOR]

Human polymorphs have been found to ingest a wide variety of particles without the aid of serum, indicating that the cells possess a serum-independent mechanism of phagocytosis. Polymorphs have also been shown to possess a different and complementary mechanism of phagocytosis which depends on the presence of serum and serum components in the medium. Ingestion of starch particles by human polymorphs in the absence of serum was unaffected by media at the extremes of physiological pH and at tonicities between 205 and 348 m-osmoles/1 and by the presence in media of neutral and acid mucopolysaccharides. Phagocytosis of starch particles was reversibly inhibited by media of high tonicity and irreversibly inhibited by low concentrations of bacterial lipopoly-saccharide, which had a lethal effect on the cells. Serum was unable to promote phagocytosis by polymorphs in media of high tonicity but both untreated serum and inactivated serum promoted phagocytosis in media containing endotoxin, probably by neutralizing the action of the lipopolysaccharide. Phagocytosis of starch particles by human polymorphs in the absence of serum was inhibited by prior treatment of the cells with iodoacetate, suggesting that serum-independent phagocytosis relies on glycolytic energy. Ingestion of starch particles by polymorphs, treated with iodoacetate, was largely contingent on the presence of serum in the suspending medium, but inactivated serum and individual plasma proteins also had a limited ability to promote phagocytosis. These results suggested that cell glycolysis is not the principal source of energy in the serum-dependent mechanism of phagocytosis. Using hydrocarbon test particles, it was shown that combinations of either of the heat-labile components of complement (C′1 or C′2) with the C′4 component were active in promoting phagocytosis. Evidence was also presented that the C′3 component had some activity and another serum factor, which was only present in the heat-inactivated sera of some individuals, also had a limited ability to promote phagocytosis. [ABSTRACT FROM AUTHOR]

Muscle fiber groups from feta, neonatal, infant, and adult rhesus monkeys (Macaca mulatta) were incubated in glycylglycine and bicarbonate buffered media plus glucose-C[sup 14]. Results obtained with these two media were similar. The metabolic data were calculated with noncollagenous nitrogen as a reference base. Under aerobic conditions the QO[sub 2] and CO[sub 2] productions were higher at 89 and 90 days fetal age, similar at 120 to 129 days, and lower at 150 to 160 days that those of adult muscle. Glucose uptake was higher at 89 to 90 days and 120 to 129 days fetal age than that of the adult series. Variations in the above parameters demonstrate that results on fetal metabolism must be reported for specific gestational periods. Lactate and lactate-C[sup 14] productions were higher in all three fetal series, and pyruvate and pyruvate-C[sup 14] productions were higher in the earlier fetal series than in those of the adult. The sum of C[sup 14] activities appearing in lactate, pyruvate, and CO[sub 2] was higher in rapidly growing muscle than in adult muscle. These data suggest that aerobic glycolysis is more active in fetal and neonatal than in adult muscle. Birth did not cause a significant change in any metabolic parameter. The relative increases, under hypoxic conditions, in glucose uptake and lactate and lactate-C[sup 14] productions in fetal compared with the increases in adult muscle suggest that the glycolytic pathway in of fetal muscle does not respond more effectively to hypoxia. [ABSTRACT FROM AUTHOR]

Optimum conditions for the in vivo nitrate reductase assay in soybean (Glycine max (L.) Merr.) foliage were determined. The in vivo and in vitro nitrate reductase assays correlated highly but exhibited differential decay rates with increasing leaf age. Nitrate reduction could be coupled to the oxidation of either frustose-1,6-diphosphate or 6-phosphogluconate. Compounds, such as glucose, 2,4-dinitrophenol or phosphate, which stimulate glycolysis also stimulated nitrate reduction. Citrate stimulated nitrate reduction in young expanding leaves but was inhibitory in mature, expanded leaves. Caffeic acid was inhibitory in young but not in mature leaves. [ABSTRACT FROM AUTHOR]

Cell-free extracts from autotrophically grown Chlorella convert glycerate to pyruvate by the reactions of glycolysis. It has already been demonstrated that exogenous glycollate is metabolized to glycerate by the reactions of the glycollate pathway in Chlorella. The activities of the constituent enzymes of glycolysis are great enough to account for the further metabolism of glycerate formed during the metabolism of exogenous glycollate by Chlorella. [ABSTRACT FROM AUTHOR]

Respiratory enzymes of the glycolytic, pentose-phosphate pathways and Krebs cycle were detected in cell-free preparations from cultured callus tissues of potato and artichoke tubers. Some of the enzymes functioning in glycolytic or pentose-phosphate pathways seemed to be associated with a particulate preparation. [ABSTRACT FROM AUTHOR]

The distribution and activity patterns of several enzymes of glycolytic and respiratory metabolism are considered in nineteen species of higher plants previously classified as tolerant or intolerant of experimental flooding. These results are combined with previous work on glycolysis, the inductive properties of alcohol dehydrogenase, and on tissue malic acid levels, to formulate a metabolic system of flooding tolerance. This system is based mainly on: (1) the control of glycolysis through the inductive and kinetic properties of alcohol dehydrogenase; and (2) a diversion from ethanol to malate accumulation, dependent upon the presence or absence of 'malic' enzyme. [ABSTRACT FROM AUTHOR]

Human beings may be divided into four groups by means of the interagglutination reactions of their bloods. There are different designations for the four groups. A designation is recommended by the National Research Council and other medical associations. Many bloods contain other specific substances which do not interfere with this system of grouping. In practice, it is a simple procedure to determine the grouping of an unknown blood. The blood groups are usually determined at birth, once established they are permanent. The frequencies of the specific substances vary in different races. Of extraordinary interest, these substances are present in the blood of anthropoid apes, but not of the lower monkeys.

The article offers a study on the enzymes in the skin of human beings. It says that aldolase is a typical enzyme for the glycolysis and that among the enzymes that originate from the citric acid cycle in the epidermis include isocitric-dehydrogenase, fumarase, and succinic-dehydrogenase. It states that lactic dehydrogenase may be produced autochthonously in the epidermal cells and its distribution varies between the tissues in the pigment-forming systems and malignant melanomas.

Presents a study that presented evidence that glycolysis by tumor tissue was of sufficient magnitude to result in hyperlactic-acidemia. Implications of renal failure; Reason for the variation in the published reports of human leukemic cell lactic acid production; Characteristics of leukemic cell aerobic glycolysis.

Focuses on a case study of three siblings with myopathy associated with inability to undergo skeletal muscle glycolysis during ischemic exercise and absence of skeletal muscle phosphorylase. Symptoms of muscular tightness, pain and weakness and swelling; Myoglobinuria exhibited by one patient after exercise; Data suggesting that the disease is transmitted by an autosomal recessive mode of inheritance.

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The effect of phosphate concentration and the initial pH of bacteriologic media on acid production and bacterial growth of Streptococcus mutans was studied. There was an inhibition of acid production and bacterial growth with an increase in concentrations of phosphate, particularly when the initial pH of the media was 8.0. At a pH of 6.5 the effect was minimal. [ABSTRACT FROM AUTHOR]

Respiratory inhibition by cyanide was measured in bovine dental pulp slices and in bovine kidney cortex slices. Although inhibition in kidney slices was approximately 80%, inhibition in dental pulp was about 60%. The lower level of respiratory inhibition in pulp by cyanide is indicative of a lower concentration of cytochrome oxidase in this tissue. This is compatible with previously observed metabolic characteristics suggestive of a less highly developed respiratory mechanism in dental pulp. [ABSTRACT FROM AUTHOR]

Successive manometric determinations of oxygen, aerobic carbon dioxide, and anaerobic carbon dioxide quotients for the same samples of bovine dental pulp indicated that glucose depresses the oxygen consumption rate and that respiration depresses the rate of glycolysis. Respiration and glycolysis proceeded at higher rates in dentinogenically active pulp than in inactive pulp. Although the pulp is capable of prominent anaerobic glycolysis, it can be sustained at high levels only with respiratory support. [ABSTRACT FROM AUTHOR]

The article focuses on lactate dehydrogenase (LDH) of developing molar teeth of laboratory mice. The role of LDH in the glycolytic pathway is that it mediates the transfer between lactic acid and pyruvate, using nicotinamide adenine dinucleotide (NAD+) as coenzyme. Information on the presence of this enzyme in the tooth may give insight into the enzymatic mechanisms responsible for the morphologic and chemical changes happening during dentition. INSET: .

This article discusses the glycolytic activity of the tooth germ during dentogenesis. The enamel and dental papilla producing sections of the cattle tooth germs were investigated. The changing levels of glycogen and lactic acid contained in the tooth germs of bovines during the production of enamel and papilla are considered.

The article presents a study which examined metabolism of glucose in the dental pulp of bovine teeth. The anaerobic glycolysis of bovine dental pulp in various stages of tooth development is discussed. The study traced glycolytic activity by measuring the formation of lactic acid in triturated dental pulp.

This article discusses the results of a research study conducted to determine the influence of 64 organic phosphorus compounds on glycolysis by micro-organisms in human saliva. The study finds that the compounds that actively inhibited glycolysis exhibited carbon to phosphorus ratios of 12-16, or exhibited tertiary amine or quaternary groupings.