ヒマ発芽種子胚乳のクエン酸合成酵素アイソザイムとその性質

概要

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By cellulose acetate gel electrophoresis and DEAE-cellulose column chromatography, two distinct citrate synthase [citrate oxaloacetate-lyase (CoA-acetylating), EC 4. 1. 3. 7] isozymes were isolated from castor bean endosperm. Mitochondria and glyoxysomes were isolated by sucrose density gradient centrifugation. The first and second peaks of citrate synthase activities of DEAE-cellulose column chromatography corresponded electrophoretically with the bands obtained from the glyoxysomes and mitochondria respectively. The optimum pH values for the two isozymes were 8.0 to 8.1 similarly, but kinetic properties were different. The Michaelis constants for acetyl-CoA and oxaloacetate of the mitochondria) citrate synthase (M-CS) at pH 8.0 were 3.4×10-5M and 0.83×10-5M, respectively. Those of the glyoxysomal citrate synthase (G-CS) were 8.5×10-5M and 4.5×10-5M, respectively. Metabolites such as citrate, glyoxylate, and succinate partially inhibited the isozymes. The degree of inhibition was stronger with M-CS than with G-CS.
社団法人日本農芸化学会の論文