HETEROGENEITY OF ERYTHROCYTE CATALASE - DISSOCIATION, RECOMBINATION AND HYBRIDIZATION OF HUMAN ERYTHROCYTE CATALASES

Dissociation of the erythrocyte catalase [EC 1.11.1.6] tetramer into its dimer form proceeds readily in urea: the rate depends on urea concentration and time of inactivation and temperature, but is not influenced by enzyme concentration. This process is accompanied by loss of catalase activity, generation of peroxidase [EC 1.11.1.7] activity and an alteration of antigenic properties. Recombination of dimer subunits to the tetramer molecule can be accomplished by removing urea by dialysis. Under optimal conditions up to 80% of the original catalase activity can be recovered. The reconstituted material is identical with the native catalase regarding enzymatic and antigenic properties but differs with respect to electrophoretic mobility and heat stability. Normal human erythrocyte catalase and the enzyme species present in blood of individuals heterozygous for Swiss-type acatalasemia differ with regard to electrophoretic mobility and heat stability. Dissociation of the heterozygote catalase tetramer into dimer subunits occurs at lower urea concentrations when compared to the normal enzyme. Since heterozygote erythrocyte catalase exerts properties intermediate to those of the normal enzyme and of the variant found in homozygotes for acatalasemia, this enzyme species is considered to represent a molecular hybrid. Hybridization of catalases can be accomplished in vitro by dissociating a mixture of normal and heterozygote catalase preparations in 8 M urea and subsequent dialysis. The resulting enzyme species reveals intermediate electrophoretic mobility and heat stability when compared with its native constituents.