The Effects of Oxyanions on the Activity of Oxalate Oxidase

Oxalate oxidase catalyzes the conversion of oxalic acid and molecular oxygen to carbon dioxide and hydrogen peroxide. Oxalate-degrading enzymes are of interest for various applications including clinical analysis of the levels of oxalic acid in blood and urine and control of oxalic acid in industrial processes, such as pulp and paper manufacture. In these applications, the presence of oxyanions other than oxalate may affect the enzyme activity. The inhibitory effect of selected oxyanions on oxalate oxidase from barley was investigated. Seven out of fourteen of the compounds studied inhibited oxalate oxidase at a concentration of 1 mM. Perchlorate, chlorate and chlorite were selected for more detailed studies. The results indicate that perchlorate, chlorate and chlorite cause mixed inhibition of oxalate oxidase and that the severity of the inhibition within the series increases with the oxidation state. The apparent KM of the enzyme was 0.28 ± 0.05 mM.