Fat Metabolism in Higher Plants. XVII. Metabolism of Malonic Acid & Its α-Substituted Derivatives in Plants

Abstract

An acyl-CoA carboxylase from wheat germ, which formed malonyl-CoA and its [alpha]-substituted derivatives, was previously described. The same enzyme was shown to catalyze ATP-independent transcarboxylations. The present communication describes the preparation and some of the properties of a malonic thiokinase, a malonyl-CoA thioesterase, and a malonyl-CoA decarboxylase from wheat germ. These enzymes were also active with methylmalonate or its CoA derivative. In view of their importance as carboxylase and transcarboxylase substrates, it was of interest that the CoA derivatives of acetate, propionate, and butyrate were formed by thiokinases present in wheat germ. The activity of these enzymes, including the carboxylase and transcarboxylase, was examined in a wide variety of plant tissue extracts. This survey indicated that enzymes for the synthesis and breakdown of malonic acid are widely distributed. The possible role of these enzymes in the control of metabolic processes, and of methyl-malonate as a metabolite, is discussed.