RATE OF OXALATE BIOSYNTHESIS FROM GLYCOLATE AND ASCORBIC-ACID IN SPINACH LEAVES

The contribution of glycolate as a precursor of oxalate in newly expanding spinach leaves was compared with that of L-ascorbic acid (ASA). Detached spinach leaves were fed with [2-C-14]glycolate and [1-C-14]ASA. Using the values of the rate of photorespiratory glycolate synthesis and the incorporation of glycolate-C-14 into oxalate, the rate of oxalate biosynthesis via glycolate amounted to 34 mug g-1 fr wt h-1 under light conditions. When the values of incorporation of ASA-C-14 into oxalate and the turnover rate of ASA were used, the rate of oxalate biosynthesis via ASA in light and darkness, amounted to 1.6 and 2.9 mug g-1 fr wt h-1 respectively. Glycolate was found to be more efficient as a precursor of oxalate than ASA in newly expanding spinach leaves.