Oxidative decarboxylation of glycollate and glyoxylate by leaf peroxisomes

1. The conditions under which peroxisomal preparations from leaves of spinach beet and spinach catalyse the release of 14CO2 from [1-14C]glycollate and [1-14C]glyoxylate were investigated. 2. At pH8, 14CO2 production from [1-14C]glyoxylate was accompanied by equivalent quantities of formate. The accumulation of oxalate and the effects of various reagents, especially catalase inhibitors, show that glyoxylate is non-enzymically oxidized by H2O2, which is generated by the oxidation of glyoxylate to oxalate by the action of glycollate oxidase. 3. 14CO2 is shown to be generated from [1-14C]glycollate at pH8 by a similar reaction, but the H2O2 is generated mainly by the oxidation of glycollate to glyoxylate. 4. The physiological significance of these reactions is discussed, with special reference to their role in photorespiration.