Purification and properties of an oxalate oxidase from leaves of grain sorghum hybrid CSH-5.

An oxalate oxidase (EC 1.2.3.4), which catalyzes aerobic oxidation of oxalate to CO2 and H2O2, has been purified to apparent homogeneity from 10-day-old leaves of grain sorghum hybrid CSH-5, as determined by disc-gel electrophoresis. The molecular weight of the enzyme was about 120,200 by Sephadex G-200 gel filtration, 62,000 by SDS disc-gel electrophoresis. The enzyme had an optimum pH of 5.0 and activation energy of 4.4 kcal/mol. The rate of reaction was linear up to 2 min. The Km value for oxalate was 0.78.10(-4) M. The enzyme was inhibited by EDTA, L-cysteine and sodium azide, but iodoacetate had no effect. The enzyme was strongly stimulated by Cu2+ and was unaffected by chloride ions in physiological concentration range. The better suitability of the enzyme for urinary oxalate determination is demonstrated.