The Fixation of Carbon Dioxide in a Plant Tricarboxylic Acid System

A preparation from parsley root has previously been shown to contain a reversible oxalacetic carboxylase and a malic dehydrogenase, and to be capable of fixing CO2 in dicarboxylic acids.1 Evidence is presented here that, this same parsley root preparation contains an oxalosuccinic carboxylase and an isocitric dehydrogenase, and is capable of fixing COZ in the tricarboxylic acids.Decarboxylation of oxalosuccinic acid by parsley root preparation.Experimental conditions: 7.8 mg. of parsley root protein in total volume of 2.0 ml.; 0.125 M acetate buffer, pH 5.5, and 5 X 10e4 M MnCL Oxalosuccinic acid, kindly supplied by Dr. S. Ochoa, tipped in from side arm to start reaction.COz evolution measured manometrically at 20" under anaerobic conditions.