Oxaloacetate Decarboxylase Activity Research Articles

Lactate metabolism by Veillonella parvula.

A strain of Veillonella parvula M4, which grows readily in lactate broth without a requirement for carbon dioxide, has been isolated from the oral cavity. Anaerobic, washed cells of this organism fermented sodium lactate to the following products (moles/100 moles of lactate): propionate, 66; acetate, 40; carbon dioxide, 40; and hydrogen, 14. Cells grew readily in tryptone-yeast extract broth with pyruvate, oxaloacetate, malate, and fumarate, but poorly with succinate. The fermentation of pyruvate, oxaloacetate, or lactate plus oxaloacetate by washed cells resulted in the formation of propionate and acetate in ratios significantly lower than those observed with lactate as the sole carbon source. This was primarily due to increased acetate production. Cell-free extracts were unable to degrade lactate but metabolized lactate in the presence of oxaloacetate, indicating the presence of malic-lactic transhydrogenase in this organism. Lactic dehydrogenase activity was not observed. Evidence is presented for oxaloacetate decarboxylase and malic dehydrogenase activities in extracts.

ENZYMES OF THE TRICARBOXYLIC ACID CYCLE IN ACETIC ACID BACTERIA.

Summary: The activities of seven enzymes which catalyse reactions of the tricarboxylic acid cycle were assayed in extracts of five lactaphilic and five glycophilic strains of acetic acid bacteria. Except for isocitrate dehydrogenase (which was not detected in glycophilic extracts) all other enzymes were found in all strains; but in general these enzymes were much more abundant in the lactaphilic extracts. In particular, extracts of glycophiles possessed only feeble citrate synthase, aconitate hydratase, fumarate hydratase and l-malate dehydrogenase activities and only their 2-oxoglutarate and succinate dehydrogenase activities were comparable to the corresponding activities in extracts of lactaphiles. Oxaloacetate decarboxylase activity was also greater in lactaphiles than in glycophiles. Two enzymes which oxidized l-malate were found: that in Acetobacter acidum-mucosum was an NADP-linked dehydrogenase, while the other more generally distributed enzyme required no added co-factors and may be cytochrome-linked. The evidence indicates that the tricarboxylic acid cycle may make a greater quantitative contribution to the metabolism of lactaphilic than to that of glycophilic organisms.