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The formation of the arginine dihydrolase pathway enzymes in Lactobacillus buchneri NCDO, a heterofermentative organism, was investigated. The specific activities of arginine deiminase, ornithine transcarbamylase, and carbamate kinase were higher in galactose-grown cells than in glucose- or sucrose-grown cells in the early stationary phase of growth. The addition of arginine to growing cells increased the specific activity of these three enzymes with all growth sugars. The specific activities of the enzymes decreased during the stationary phase of growth when the sugar-grown cells was galactose. When glucose was virtually exhausted from the medium, the activities of the three enzymes were not altered. This enzymic system was not repressed by glucose, and these results are different from those obtained with L. leichmanni, homofermentative organism. [ABSTRACT FROM AUTHOR]

Lactobacillus leichmannii ATCC 4797 metabolizes arginine via the arginine dihydrolase pathway producing ornithine, ammonia, carbon dioxide, and ATP. The specific activities of arginine deiminase and ornithine transcarbamylase were two-or threefold lower (stationary growth phase) in galactose-grown cells. The addition of arginine increased the specific activities of these two enzymes with all growth sugars. When glucose was virtually exhausted from the medium, maximum activities of both enzymes were achieved. The formation of two first enzymes of the arginine dihydrolase pathway in L. leichmannii ATCC 4797 seems to be under the control of two processes: induction by arginine and repression of the induced synthesis by glucose. [ABSTRACT FROM AUTHOR]

Ornithine transcarbamylase (OTCase) (E.C.2.1.3.3) was partially purified from Lactobacillus buchneri NCDO. It was stabilized by the presence of glycerol. The optimal pH for enzyme activity is 8.5. The positive cooperativeness was observed among ornithine molecules at pH values different from the optimum. The Mr of the enzyme was calculated to be 162,000 by gel filtration on Ultrogel ACA-34. Maximum activity occurred at 35°C. ΔG of the reaction was calculated from Arrhenius plot. The values were 9100 cal mol below 35°C, and 4300 cal mol above 35°C. The Km value for carbamylphosphate was 7.1×10 M, and the Km for ornithine was 1.6×10 M, under the conditions described here. Dead-end inhibition analysis was performed with norvaline, which is a structural analogue of ornithine. Norvaline acted as a noncompetitive inhibitor when carbamylphosphate was the variable substrate, and as a competitive inhibitor when ornithine was the variable substrate. The results are consistent with a ping-pong mechanism. [ABSTRACT FROM AUTHOR]

The effect of saturated fatty acids from 6∶0 to 16∶0 and oleic acid on Lactobacillus leichmanii ATCC 4797 growing in non-skim-milk media was determined. The inhibition by lauric acid was higher than that obtained with any other fatty acid. A mutant (MC12) resistant to the fatty acid inhibition with high β-oxidation activity was also studied. A positive correlation between the ability of L. leichmanii ATCC 4797 and its derivative MC12 to degrade fatty acids and their resistance to the fatty acid inhibition is shown in this report. [ABSTRACT FROM AUTHOR]

β-Galactosidase has been isolated in Lactobacillus murinus CNRZ 313, and its properties have been studied. The enzyme was purified 292-fold by chromatography on Ultrogel ACA 34, DEAE-Sephadex A-50 columns, and by affinity chromatography in agarose- p-aminophenyl-β- d-thiogalactoside. The purified extract exhibited a single band following polyacrylamide gel electrophoresis (PAGE). Molecular weight was estimated to be 170,000 on an Ultrogel ACA 34 column. Maximum enzymatic activity was observed at 45°C and pH 7 in 50 mM phosphate buffer. The Km for ONPG and ONPG + 20 mM of lactose were 480 μM and 870 μM, respectively. The effect of different salts on the enzymatic activity was studied. An inhibitory effect was observed when using 10 mM CaCl, and a stimulating effect when using 10 mM MgCl. The latter protected the enzyme from thermal denaturation. Among the protective agents belonging to the sulfhydryl group that was tested, mercaptoethanol and dithiotreitol acted as activators, while glutathione and cysteine acted as inhibitors, of the enzymatic activity. p-β-Galactosidase activity was not observed. [ABSTRACT FROM AUTHOR]

The effect of saturated fatty acids from 6∶0 to 16∶0 and oleic acid was determined on Lactobacillus leichmannii growing in skim milk. The growth of this strain was markedly inhibited by fatty acids from 8∶0 to 12∶0 but not by straight chain fatty acids greater than 13∶0 or less than 7∶0 and oleate. Laurate was the fatty acid with the highest bactericidal effect. Similar results, with little changes depending on strains, were obtained with L. casei, L. plantarum, L. bulgaricus, L. lactis, L. helveticus. Mutants from these Lactobacillus organisms, resistant to fatty acid inhibition, were isolated by a recycling selection procedure. These mutants exhibited high levels of oxidation for laurate. The presence of 2 mM of this compound in the skim milk culture increased the fatty acid oxidation activity four to ten times higher than was exhibited by the parent strains. The practical implications of these observations are discussed. [ABSTRACT FROM AUTHOR]

The influence of soybean galactosaccharides (stachyose, raffinose, melibiose) as well as galactose and glucose on the synthesis and activity of α-galactosidase (α-gal) from Lactobacillus fermentum CRL 251 was studied. Stachyose was the most effective inducer, followed by melibiose, raffinose, and galactose; scarce activity was detected with glucose. Exogenously supplied glucose inhibited the synthesis of the enzyme in cultures of L. fermentum growing on galactose. This effect was reversed by the addition of cyclic adenosine-3′,5′ monophosphate (cAMP), which suggests that this compound could be involved in the regulation of α-gal synthesis. [ABSTRACT FROM AUTHOR]

l-Serine dehydratase from Lactobacillus fermentum was purified 100-fold. It was stabilized by the presence of 1 m M l-cysteine in 50 m M phosphate buffer. M=150,000 was determined by gel filtration. The enzyme consists of four apparently identical subunits (M=40,000) that were observed after treatment with sodium dodecyl sulfate. The apparent K for l-serine was 65 m M. Fe was required for the enzymatic activity, and the apparent K value for this reaction was 0.55 m M. Maximum enzymatic activity was observed at 45°C and pH 8.0 in 50 m M phosphate buffer. At pH values different from the optimum, a positive cooperativity between substrate molecules was observed. The activation energy of the reaction was 11,400 and 22,800 cal × mol for temperature values more than and less than 35°C respectively. The purified enzyme showed a maximum absorption between 400 and 420 nm, indicating the presence of pyridoxal-5′-phosphate (PLP) as a prosthetic group. The PLP concentration was 0.027 µmoles per milligram of protein. The data suggest that there is 1 mol of PLP for each protein subunit. [ABSTRACT FROM AUTHOR]

Lactic acid or its acidity apparently play an important role in the regulation of the biosynthesis of flavor compounds in Lactobacillus casei subsp. rhamnosus ATCC 7469. In pyruvate-containing media, L. casei produces lactic acid, acetoin, and diacetyl. A specific pH-dependent system is necessary for both the use of pyruvate and the induction of acetoin and diacetyl production. In cell extracts of L. casei, lactic acid inhibits the enzymatic activity of acetolactate decarboxylase (ALD) and acetolactate synthetase (ALS); this effect does not occur in whole cells under standard physiological conditions. Lactic acid prevents the use of pyruvate, and the induction of acetoin and diacetyl production. When pyruvate-containing media are used, the pH must be kept close to 6.0 in order to obtain the best production of acetoin and diacetyl. [ABSTRACT FROM AUTHOR]

The characteristics of pyruvate utilization in Lactobacillus casei subsp. rhamnosus ATCC 7469, grown in synthetic medium with 33 m M glucose and 100 m M pyruvate, were investigated. This lactobacillus utilizes a transport system that depends on the presence of glucose and presents a saturation kinetics of 33 m M Km and a Vmax of 1 μmol/5 min/mg dry weight. It has an optimum pH of 6.0 and an optimum temperature of 37°C. It is present in a synthetic medium without pyruvate, so that it is constitutive. It is not inhibited by glucose when this is added to the synthetic growth medium at a concentration of 1 g%. It is specific for pyruvate. [ABSTRACT FROM AUTHOR]