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The authors investigated the nitrogen content of different fractions and in particular the aminoacid composition of the trichloroacetic acid (TCA)-precipitable and TCA-soluble peptides in the distal small intestine of rats which had been fed experimental diets (nitrogen-free or containing casein, wheat gluten or molasses yeast as a protein carrier). Parallel with this, they determined in growing rats the nitrogen and amino-acid digestibility of molasses yeast and wheat gluten according to the technique of faecal analysis, and studied the amino-acid composition of the faecal protein. Independently of the dietary protein fed, the peptide fractions of the content of the intestine showed an amino-acid composition that was largely similar to that found in case of nitrogen-free diet. The amino-acid composition of the faecal protein is, independently of the dietary protein given, relatively constant and corresponds approximately to the intestinal loss protein. There is agreement between the amino-acid composition of the TCA-precipitable peptide fractions and those of the corresponding faecal proteins. These components seem to be of endogenous origin. more...

The reaction of dialdehyde starch with the proteins of certain model protein texturates produces changes in the nutrition physiological quality of the proteins. Under the experimental conditions chosen, these changes were barely or not at all detectable by amino-acid analysis. On using the technique of aminoacid liberation under in vitro conditions, these changes were evidenced only for lysine and arginine. The determination of the lysine availability, however, testifies to a reversible or irreversible change of lysine which reduces significantly the PER values (animal experiments) of protein texturates treated with 100% oxidized dialdehyde starch. The differences between the NPU values were but insignificant. In spite of the detectable change in protein quality, the quality of the model protein texturates tested still satisfies the criteria for proteins with a composition which is favourable from the viewpoint of nutrition physiology. more...

The microvilli-bound leucine arylamidase is inhibited by certain amino acids. An inhibitory action is exerted by the branched-chain amino acids L-leucine and L-isoleucine and by the aromatic amino acids L-tyrosine and L-phenylalanine with Ki values of 4--6 . 10(-3) M. L-methionine (Ki = 2.5 . 10(-3) M) and its higher homologue L-ethionine (Ki = 1.1 . 10(-3) M) are the most potent inhibitors. Derivatization of L-methionine on the sulphur or the nitrogen atom or the carboxyl group prevents the inhibitory effect just as the D-isomer. more...

Es wird ein Uberblick uber die Ultrastruktur der Dunndarmepithelzelle, insbesondere uber deren lumenwartige Membran, gegeben. Dabei wird auf die in der Burstensaumregion und im Zellinneren lokalisierten Peptidasen eingegangen. Es wird die Reinigung der fur die Spaltung von Nahrungspeptiden wichtigen membrangebundenen Aminopeptidase besprochen und ihre Spezifitat am Beispiel der Caseinspaltung erlautert. Die wahrend der Peptidspaltung entstehenden freien Aminosauren besitzen teilweise einen Inhibitoreffekt auf die Aminopeptidase. Die moglichen verdauungsphysiologischen Konsequenzen werden diskutiert. Im In-vivo-Versuch wurde der distale Dunndarminhalt von Ratten im Hinblick auf die Zusammensetzung von Peptiden in Abhangigkeit von der Zusammensetzung verschiedener Nahrungsproteine untersucht. Die Zusammensetzung der Peptide des Darminhaltes ist im wesentlichen unabhangig von der Aminosaurenzusammensetzung der Nahrung; es erfolgt keine deutliche Anreicherung bestimmter Aminosauren. Die Bedeutung der Resorption von Peptiden wird auch in vergleichenden Resorptions-untersuchungen deutlich, in denen enzymatische Hydrolysate von Proteinen, also Peptidgemische, der Mischung freier Aminosauren gleicher Gesamtzusammensetzung gegenuber-gestellt werden. Am Beispiel des Glycyl-glycin-glycin wird dargestellt, das in bestimmten Konzentrationsbereichen auch Tripeptide teilweise intakt resorbiert werden konnen. Abschliesend wird die Bedeutung der Peptidresorption eingeschatzt, und es werden Konsequenzen fur weitere Untersuchungen zur Physiologie und Pathophysiologie der Verdauung gezogen. more...

Tryptic, thermitatic, and tryptic-thermitatic Faba bean protein hydrolyzates as well as their equimolar mixture of amino acids were perfused through proximal and distal parts of the intestine (10 cm length) of non-narcotized rats. The total amino-acid concentration of the perfused solution was 50 mM. The absorption of nitrogen and total amino acids from the tryptic and tryptic-thermitatic hydrolyzates was lower than that from the amino-acid mixture, the absorption from the thermitatic hydrolyzate was in accordance with that from the amino-acid mixture. The absorption pattern of the amino acids which preferably undergo a peptidic absorption is similar with the three hydrolyzates: in the proximal intestinal part this concerns glutamic acid and serine, in the distal intestinal part--methionine, alanine, glycin, and serine. The absorption pattern of the amino acids is different between the three hydrolyzates and the amino-acid mixture. Between the absorption pattern of the amino acids from the three hydrolyzates little differences were evident only in the proximal intestinal part. The coefficients of variation of the tryptic-thermitatic hydrolyzates are in accordance with those of the amino-acid mixture, whereas that of the thermitatic hydrolyzates is significantly lower. In the distal intestinal part all supplied forms are more rapidly absorbed than in the proximal part of the intestine. more...

Der exopeptidatische Abbau von Peptidgemischen durch die Aminopeptidase der Burstensaume wird durch die Anwesenheit freier Aminosauren gehemmt. Nach Entfernung der freien Aminosauren aus dem Peptidgemisch erfolgt eine weitergehende Spaltung. Die Aminosaurezusammensetzung der verbleibenden Restpeptide stellt einen zweiten Faktor dar, der einer vollstandigen Spaltung der Peptide entgegensteht. more...

Tryptic, thermitatic, and tryptic-thermitatic wheat-gluten hydrolyzates as well as their equimolar amino-acid mixture were perfused through proximal and distal parts of the intestine (10 cm length) of non-narcotized rats. The total amino-acid concentration of the perfused solution was 50 mM. The tryptic hydrolyzate showed a significantly lower absorption of nitrogen and total amino acids than the amino-acid mixture. Both the supplied forms were very different as to their absorption pattern of the amino acids. The high variability of the percental absorption of the individual amino acids of the tryptic hydrolyzate results in a high coefficient of variation. The absorption of nitrogen and total amino acids from thermitatic and tryptic-thermitatic hydrolyzates is equal to that from the amino-acid mixture. In a peptidic form glutamic acid is more rapidly absorbed from the two hydrolyzates, and methionine from the tryptic-thermitatic hydrolyzate in both the intestinal parts. As to alanine and glycine this concerns only the distal intestinal part for both the hydrolyzates. There are no differences between the absorption patterns of the two hydrolyzates but in comparison with the amino-acid mixture and the tryptic hydrolyzate differences were evident. The coefficients of variation of both the hydrolyzates are significantly lower as compared to those of the tryptic hydrolyzate and the amino-acid mixture. All forms of supply are more rapidly absorbed in the distal than in the proximal part of the intestine. more...

Die membrangebundene Leucinarylamidase der Burstensaume des Rattendunndarms wurde durch Triton X-100 solubilisiert und durch Gel- und Ionenaustauschchromatographie gereinigt. Die Reinigung gegenuber dem Mucosahomogenat erfolgte um den Faktor 135. Leucinarylamidase und Aminotripeptidase der Burstensaume sind chromatographisch nicht zu trennen. Der cytosomale Anteil der Aminotripeptidase besitzt keine Leucinarylamidaseaktivitat. more...

Die Nahrungen bestanden aus Futter mit 20% Proteinanteilen aus Casein, Proteinisolat aus Sonnenblumensaat, Proteinisolat aus Ackerbohne, einem Modellproteintexturat unter Verwendung von Ackerbohnenproteinisolat, einem Modellproteintexturat unter Verwendung von mit Dialdehydstarke behandeltem Ackerbohnenproteinisolat sowie N-freiem Futter. Der distale Dunndarminhalt der Ratten wurde 3 h nach der Nahrungsaufnahme gewonnen und die Aminosaurezusammensetzung der Trichloressigsaure (TCE-)-fallbaren Peptide und der TCE-loslichen, von freien Aminosauren abgetrennten Peptide des Darminhaltes untersucht. Der Vergleich der Aminosaurezusammensetzungen der beiden Peptidfraktionen mit dem jeweiligen Nahrungsprotein zeigt keine Ubereinstimmung, der Vergleich der beiden Peptidfraktionen nach N-freier Diat mit den jeweiligen Peptidfraktionen nach Proteinaufnahme zeigt unabhangig vom Nahrungsprotein ein hohes Mas an Ubereinstimmung, und der Vergleich der beiden Peptidfraktionen untereinander zeigt einen hoheren proteolytischen Abbaugrad der TCE-loslichen Peptide. Ackerbohnenproteinhaltige Diaten fuhren im Vergleich zu den anderen Proteindiaten und N-freier Diat zu einer Zunahme TCE-fallbarer Peptide und zu einer Zunahme von Glycin in beiden Peptidfraktionen. Dieses Verhalten zeigt sich auch in den Modellproteintexturaten, die nur 30% Ackerbohnenprotein enthalten. Eine Behandlung mit Dialdehydstarke fuhrt zu einer gewissen Schadigung von basischen Aminosauren und deren Anreicherung in den unverdauten Peptidfraktionen. more...

Pseudofette auf der Basis vollstandig substituierter langkettiger Ester und Ether von Polyhydroxyverbindungen (Saccharose, Triglycerol und Polyethylenglycol) verhalten sich mehr oder weniger indifferent gegen-uber gastrointestinalen Enzymsystemen, entfalten aber zugleich spezifische metabolische Wirkungen auf den Lipidstoffwechsel, insbesondere auf die Cholesterolsynthese in der Leber, den Lipidspiegel des Serums und die fakale Cholesterolexkretion. Zwischen den getesteten verschiedenartigen Verbindungen bestehen Gemeinsamkeiten und Unterschiede, die als Indizes fur eine Struktur-Wirkungsspezifitat zu werten sind. Diesbezugliche Beziehungen werden im Rahmen der Arbeit naher untersucht und kritisch beleuchtet. more...

After feeding with protein containing diets the protein quantity increases in the aqueous supernatant (U1), in the trichloracetic acid soluble (U2) and precipitable (S2) fractions of the content of the distal part of the small intestine of rats. Independent of the dietary proteins the amino acid composition of both fractions (S2 and the peptides from U2) is similar in relation to protein-free feeding; a similarity with the amino acid composition of the dietary proteins doesn't exist. In relation to fraction S2 the peptides of fraction U2 show anording to the higher content of amino acids, which are difficult to liberate by protein cleavage, a high proteolytic degradation. more...

Zur Untersuchung gelangten die Proteine Casein, Weizengluten und Ackerbohnenproteinisolat (Vicia faba). Diese Proteine wurden jeweils durch Trypsin, durch Thermitase sowie nacheinander durch Trypsin und Thermitase gespalten. Thermitase ist eine aus Thermoactinomyces vulgaris gewonnene mikrobielle Protease mit einer Affinitat gegenuber einem breiten Spektrum von Peptidbindungen. Bei samtlichen enzymatischen Proteinhydrolysen treten keine freien Aminosauren auf. Die Spaltungsgrade fur tryptische Hydrolysate von Casein, Weizengluten und Ackerbohnenprotein liegen bei 18%, 8% bzw. 16%. Die Spaltungsgrade nach thermitatischer bzw. tryptisch-thermitatischer Hydrolyse liegen fur alle drei Proteine zwischen 30% und 35%. Es werden die Peptidgrosen in den Proteinhydrolysaten nach Gelchromatographie an Sephadex G-25 ermittelt und ihre quantitativen Anteile im jeweiligen Hydrolysat berechnet. more...

An 4 verschiedenen Proteinisolaten aus Ackerbohnen (Vicia faba) und 2 Ackerbohnenprotein-Casein(1:1)-Fasern werden mittels Bestimmung der Aminosaurezusammensetzung, der enzymatischen Aminosaurefreisetzung (in vitro) und der biologischen Wertigkeit (Ratte) Aussagen zum ernahrungsphysiologischen Wert dieser Proteine gemacht. Die Aminosaurezusammensetzungen verschiedener Proteinisolate weisen untereinander eine gute Ubereinstimmung auf. Im Vergleich zu Casein fallt der niedrigere Gehalt an essentiellen Aminosauren insgesamt auf. Der niedrige Methionin- + Cystingehalt begrenzt den biologischen Wert dieser Proteine an erster Stelle. Der Lysingehalt ist als gunstig hoch anzusehen. Die enzymatische Freisetzung der Aminosauren im in-vitro-Test ergibt fur die Proteinisolate eine dem Casein vergleichbare Freisetzung insgesamt. Die Verdaulichkeit ist als sehr gut zu kennzeichnen, die biologische Wertigkeit liegt unter 50 und damit recht niedrig. Die Ackerbohnenprotein-Casein(1:1)-Fasern entsprechen, von dem geringeren Gehalt an schwefelhaltigen Aminosauren abgesehen, in ihrer Aminosaurezusammensetzung dem Erwartungswert. Sie sind damit ernahrungsphysiologisch gunstiger als die Ackerbohnenproteinisolate zusammengesetzt (hoherer Anteil an essentiellen Aminosauren). Die enzymatische Verfugbarkeit der Fasern ist ebenfalls mit der des Caseins vergleichbar. Die Verdaulichkeit im N-Bilanz-Versuch ist sehr gut, die biologische Wertigkeit der untersuchten Faserproben entspricht der von Casein. more...

Ein proteolytischer Abbau von Casein bei gleichzeitiger Ultrafiltration der Spaltungsprodukte zeigt unter den gegebenen Bedingungen keinen hoheren Spaltungsgrad als eine proteolytische Spaltung ohne Ultrafiltration oder Dialyse. Die Ultrafiltration wurde mit DIAFLO-Membranen verschiedener Porengrose durchgefuhrt. Die Spaltung wurde sowohl durch E280 des trichloressigsaureloslichen Uberstandes als auch durch Bestimmung des Zuwachses an α-Aminostickstoff durch 2,4,6-Trinitrobenzolsulfonsaure ermittelt. more...

The nutritional-physiological value of an easily soluble and of a difficulty soluble fraction of protein from Vicia faba (showing a degree of acetylation of 0%, 43% and 94%, respectively) was characterized by determining the amino-acid content, the enzymatic amino-acid availability and the nitrogen balance in the rat. The results from both the amino-acid analysis and the animal experiments on the biological value evidenced that the nutritional-physiological value of the easily soluble fraction of protein from Vicia faba is significantly lower, which is in particular attributable to its lower content of sulphur-containing amino acids. Acetylation did not reduce the nutritional-physiological value of the easily soluble fraction of protein from Vicia faba, and impaired that of the difficulty soluble fraction but slightly. From the viewpoint of nutritional physiology, there are no objections against the use of these protein fractions as food additives. more...

The possible significance of food composition connected with the alpha-glycerophosphate (alpha GP) shuttle, a putative metabolic pathway of energy dissipation, was investigated at the level of enzyme activities. Liver, adipose tissue, slow-twitch and fast-twitch muscle of weaned male Wistar rats fed ad libitum for seven and for forty weeks a normal-protein (NP), a low-protein (LP), and a high-fat (HF) diet were examined. No striking dietary influences on cytosalic (NAD-linked glycerophosphate dehydrogenase, glyceraldehyde-phosphate dehydrogenase) and mitochondrial (succinate dehydrogenase, cytochrome c oxidase) enzyme activities could be detected, but mitochondrial alpha-glycerophosphate dehydrogenase (m-GPDH) showed an about twofold increase of its activity in the liver of LP-fed animals after seven weeks. A relationship between the "gross efficiency of food energy utilization" and tissue m-GPDH levels could not be established in general. The proposed inducing effect of a LP diet on the magnitude of the GP shuttle observed in the liver of young and adult rats seems to be interconnected reciprocally with the degree of metabolic energy dissipation only under the conditions of growth. The calculated capacities of the alpha GP shuttle are compatible with the assumption of its function as an energy dissipating pathway which is restricted in its magnitude. more...

Postnatal overnutrition due to breeding of rats in small nests (4 pups per dam) leads to distinct metabolic changes in later life stages even in conditions of ad libitum feeding. At an age of 5 months rats from small nests differ from those of large nests (14 pups per dam) in a significant higher level of liver triglycerides and cholesterol esters, whereas changes in plasma lipids concern only the increased cholesterol ester fraction. The relative distribution of in vivo incorporated C14-1-acetate into liver lipids shows a higher moiety in the triglyceride fraction of animals from small nests but no changes of the relative distribution of activity among lipid fractions of plasma. These changes of lipid metabolism are discussed in relation to the development of an obese state of postnatally overfed animals. more...

To characterize the effect of long-term supply medium-chain triglycerides on the lipid metabolism, the authors determined under postprandial conditions the ratio between the ketone body concentrations in the blood and the liver, the in vitro fatty-acid synthesis in the liver and the adipose tissue, the plasma and liver lipids and the fatty-acid and phospholipid spectra of the plasma and the erythrocytic, thrombocytic and liver mitochondrial membranes, in rats after 9 weeks on an isoenergetic diet containing 12% of medium-chain triglycerides or lard. The long-term supply of medium-chain triglycerides induced a 3-fold increase of the fatty-acid synthesis in the liver and the fatty tissue. In contrast to this, no differences in the concentrations of acetacetate and beta-hydroxybutyrate were detected in the liver and the adipose tissue. The triglyceride and cholesterol contents in the liver were significantly reduced. In spite of the increase of palmitic acid proportion as the end product of the de novo fatty-acid synthesis in the plasma lipids and the erythrocytic membrane, the proportion of essential fatty acids in the membrane lipids under study was not affected; the simultaneous supply of 3% of sunflower oil meets the requirements for essential fatty acids. more...

Die Lipid-senkenden Eigenschaften von Ackerbohnenprotein sind bisher lediglich im Tierexperiment beschrieben. Danach gilt Ackerbohneneiweis als potentester Cholesterol-Senker unter den Pflanzenproteinen. Wir untersuchten deshalb an einer kleinen Gruppe von Patienten mit Hypercholesterolamie (HLP Typ II a) den genannten Effekt und fanden signifikante hypolipidamische Wirkungen des Ackerbohnenproteinisolats, die denen vergleichbar sind, die mit Sojaproteindiaten erzielt wurden. more...

Tryptic, thermitatic, and tryptic-thermitatic casein hydrolyzates as well as their equimolar amino-acid mixture were perfused through proximal and distal parts of the intestine (10 cm length) of nonanaesthesized rats. The total amino-acid concentration of the perfused solution was 50 mM. The absorption of nitrogen and total amino acids respectively did not reveal significant absorption advantages in favour of the hydrolyzates. In contrast to this, some peptidic bound amino acids of these hydrolyzates show a significantly better absorption as compared to free amino acids. At this, dependences of the kind of hydrolyzate and the part of the intestine are evident. Glutamic acid, e.g. is generally more rapidly absorbed when peptidic bound; methionine is more rapidly absorbed only from the thermitatic and tryptic-thermitatic hydrolyzates, and alanine and glycin only in the distal part of the intestine. Independent of the amino acid or peptide substrate the total absorption of all the amino acids is higher in the distal part of the intestine. The comparison concerning the ranking order of the single amino-acid absorption rates shows in the two parts of the intestine distinct differences between the amino-acid mixtures and the enzymatic hydrolyzates. The lowest differences were found between the thermitatic and the tryptic-thermitatic hydrolyzate. Both of them have approximately the same degrees of hydrolysis (30 and 35%, respectively). The variability of the amino-acid absorption from the three casein hydrolyzates is lower in comparison with the amino-acid mixture. The tryptic-thermitatic hydrolyzates have the lowest coefficients of variability. more...

Weaned male Wistar rats were fed ad libitum besides standard pellets a normal-protein (NP), a low-protein (LP) and a high-fat (HF) diet for different periods of time. In comparison to rats on the NP diet the body weight of the LP group was significantly lower after seven weeks feeding, not after a duration of about forty weeks. No remarkable diet-related differences were detected by determination of the mean body composition and of the relative gross energy content of the body neither after seven nor forty weeks. Total gross energy intake was practically identical both for the NP and LP rats irrespective on the duration of the feeding period. A significantly lower quotient of body energy gain/total gross energy intake under the protein-restrictive LP diet after seven weeks suggests the expression of an energy dissipation obviously no longer visible after a long time feeding period. more...

Die exopeptidatische Aktivitat der drei Enzymquellen wurde anhand der Aminosaurefreisetzung eines durch Pepsin und Pankreasenzyme vorgespaltenen Caseins untersucht. Die Leucinarylamidase besitzt ein charakteristisches Spektrum an freigesetzten Aminosauren. Die Aktivitaten und Spezifitaten gereinigter Leucinarylamidase und gereinigter Burstensaume sind sehr ahnlich. more...