Cofactor-Dependent Aldose Dehydrogenase of Rhodopseudomonas spheroides

Abstract

Niederpruem, Donald J. (University of California, Berkeley), and Michael Doudoroff . Cofactor-dependent aldose dehydrogenase of Rhodopseudomonas spheroides . J. Bacteriol. 89: 697–705. 1965.—Particulate enzyme preparations of cell extracts of Rhodopseudomonas spheroides possess constitutive dehydrogenase and oxidase activities for aldose sugars, reduced nicotinamide adenine dinucleotide (NADH 2 ), and succinate. The dehydrogenation of aldoses requires an unidentified cofactor which is not required for the oxidation of succinate nor of NADH 2 . The cofactor is present in the particulate fraction of aerobic cells, but is unavailable to the enzyme system. It can be liberated by boiling or by treatment with salts at high concentration. The cofactor also appears in the soluble fraction of aerobic cells, but only after exponential growth has ceased. Extracts of cells grown anaerobically in the light possess the apoenzyme, but not the cofactor, for aldose oxidation. Cofactor activity was found in extracts of Bacterium anitratum (= Moraxella sp.) but not in Escherichia coli, Pseudomonas fluorescens , yeast, or mouse liver. In 0.075 m tris(hydroxymethyl)aminomethane-phosphoric acid buffer ( p H 7.3), the oxidation of NADH 2 was stimulated and succinoxidase was inhibited by high salt concentrations.