Heterogeneity of Erythrocyte Catalase

Abstract

Human and horse erythrocyte catalase is separated into three fractions (A, B and C) upon chromatography on DEAE‐cellulose. Fractions B and C are formed out of fraction A by oxidation of sulfhydryl groups during preparation. A purification method, including chromatographies on DEAE‐ and CM‐cellulose was devised. The whole procedure was carried out under nitrogen and in presence of EDTA, yielding the pure native enzyme (fraction A). Both the human and horse enzyme contain 16 cysteine residues per molecule, determined by titration with p ‐chloromercuribenzoate and amino acid analysis of the fully carboxymethylated or the performic acid oxidized protein. The transition of the chromatographic fraction A to fraction C is characterized either by a conformational change or by an irreversible oxidation of sulfhydryl groups to higher oxidation products.