Partial Purification and some Properties of the (R)‐Citrate Synthase from Clostridium acidi‐urici

The enzyme (R)‐citrate synthase which catalyzes essentially the same biochemical reaction as the citrate synthase but differs in its stereospecificity, has been studied. From cell‐free extracts of Clostridium acidi‐urici the enzyme has been purified 80‐fold by isoelectric precipitation and by chromatography on DEAE‐cellulose and DEAE‐Sephadex. The purification is made difficult by the instability of the enzyme. With the aid of the stereospecific cleavage of citrate by citrate lyase it was demonstrated that the purified (R)‐citrate synthase is not contaminated by the usual citrate synthase. The (R)‐citrate synthase differs in some properties from the usual citrate synthase: it is inactivated by exposure to oxygen, anaerobic conditions and a sulfhydryl compound being required for maximum activity. (R)‐citrate synthase has a specific requirement for manganese ions, the enzyme is inhibited by EDTA, and this inhibition can be reversed by manganese ions but not by magnesium ions.