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.