title: Keto acid metabolism in Desulfovibrio.
abstract: Four strains of Desulfovibrio each excreted pyruvate to a constant level during growth; it was re-absorbed when the substrate (lactate) was exhausted. Malate, succinate, fumarate and malonate also accumulated during growth. One of the strains (Hildenborough) excreted alpha-ketoglutarate as well as pyruvate when incubated in nitrogen-free medium; the former was re-absorbed on addition of NH4Cl. In a low-lactate nitrogen-free medium, strain Hildenborough rapidly re-absorbed the pyruvate initially excreted, but did not re-absorb the alpha-ketoglutarate. Arsenite (I mM) prevented the accumulation of alpha-ketoglutarate; I mM-malonate did not affect the accumulation of keto acids. Isocitrate dehydrogenase activity (NAD-specific) in all strains was lower than NADP-specific glutamate dehydrogenase activity. Alpha-Ketoglutarate dehydrogenase could not be detected in any strain. NADPH oxidase activity was demonstrated. This and previous work indicate that a tricarboxylic acid pathway from citrate to alpha-ketoglutarate exists in Desulfovibrio spp., and that succinate can be synthesized via malate and fumarate; however, an intact tricarboxylic acid cycle is evidently not present. The findings are compared with observations on biosynthetic pathways in clostridia, obligate lithotrophs, phototrophs, and methylotrophs, and various facultative bacteria.
mesh_terms: D000154:Aconitate Hydratase / Q000378:metabolism; D001151:Arsenic / Q000494:pharmacology; D002474:Cell-Free System; D002952:Citric Acid Cycle; D003901:Desulfovibrio / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D005650:Fumarates / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007651:Keto Acids / Q000378:metabolism*; D007655:Ketoglutarate Dehydrogenase Complex / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008314:Malonates / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013386:Succinates / Q000378:metabolism
chemical_list: D005650:Fumarates; D007651:Keto Acids; D007656:Ketoglutaric Acids; D007773:Lactates; D008293:Malates; D008314:Malonates; D011773:Pyruvates; D013386:Succinates; D007521:Isocitrate Dehydrogenase; D007655:Ketoglutarate Dehydrogenase Complex; D005969:Glutamate Dehydrogenase; D009247:NADH, NADPH Oxidoreductases; D000154:Aconitate Hydratase; D001151:Arsenic; D009584:Nitrogen