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 (14)CO(2) from [1-(14)C]glycollate and [1-(14)C]glyoxylate were investigated. 2. At pH8, (14)CO(2) production from [1-(14)C]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 H(2)O(2), which is generated by the oxidation of glyoxylate to oxalate by the action of glycollate oxidase. 3. (14)CO(2) is shown to be generated from [1-(14)C]glycollate at pH8 by a similar reaction, but the H(2)O(2) 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.