Assimilation of D-Malate by Rhodobacter capsulatus E1F1

Rhodobacter capsulatus grew by using either L- or D-malate as carbon source s under light/ anaerobic conditions. The cellular yields were the same with D- or L-malate. Both L-malate dehydrogenase and L-malic enzyme activities were detected in cell-free extracts from cells grown in both isomers. By co ntrast, a racemase activity converting D-malate into L-malate was induced o nly when D-malate was present in the culture medium. This racemase activity was Mn2+-dependent and was measured by coupling it either to the malate de hydrogenase or to the fumarase activities. The racemase activity was partia lly purified by anion-exchange chromatography.