Cofactor-Dependent Aldose Dehydrogenase of Rhodopseudomonas spheroides

Publisher Website
Google Scholar
Abstract
Particulate enzyme preparations of cell extracts of R. spheroides possess constitutive dehydrogenase and oxidase activities for aldose sugars, reduced nico-tinamide-adenine-dinucleotide (NADH2) and succinate. The dehydrogen-ation of aldoses requires an unidentified cofactor which is not required for the oxidation of succinate nor of NADH2. 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 (pH 7.3), the oxidation of NADH2 was stimulated and succinoxidase was inhibited by high salt concentrations.