Metabolism of l-Malate and d-Malate by a Species of Pseudomonas

Abstract

Extracts of a fluorescent species of Pseudomonas grown with m-cresol, degrade gentisic acid without isomerization of the ring-fission compound, maleylpyruvate, to give eventually d-malate and pyruvate. d-Malate is also a growth substrate. l-Malate but not d-malate is oxidized by a particulate enzyme not requiring nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP). NAD- or NADP-linked malate dehydrogenases are absent but cells contain an NADP-dependent l-malic enzyme. Exposure of cells to exogenous d-malate induces an NAD-dependent d-malic enzyme, not present when d-malate is formed endogenously. Succinate- or m-cresol-grown cells, containing no d-malic enzyme, rapidly oxidize d-malate in the presence of chloramphenicol at a concentration suffient to inhibit protein synthesis. An NADP-dependent cell-free system, prepared from succinate-grown cells which oxidized d-malate, is described.