Serum catalase: reversibly formed charge isoform of erythrocyte catalase
Góth, L.
Clinical Chemistry 37(12): 2043-2047
1991
ISSN/ISBN: 0009-9147 PMID: 1764779 Document Number: 383939
The different electrophoretic mobilities of erythrocyte and serum catalase (EC 1.11.1.6) were confirmed and the causes responsible for their differences were examined. The presence of a catalase-binding protein in serum that could form a complex with erythrocyte catalase was excluded by incubating serum proteins with erythrocyte catalase. No new unequivocal catalase bands representing a catalase-binding protein were detected. The erythrocyte and serum catalase proved to be charge isoforms: their molecular masses, estimated by gel permeation chromatography or polyacrylamide gel electrophoresis in a nondenaturing system, were very similar, whereas their electrophoretic mobilities were different. Assay of serum catalase by gel permeation and hydrophobic chromatography yielded a product with the same electrophoretic mobility as that of erythrocyte catalase. Different dilution of erythrocyte catalase with human sera led to a gradual decrease of its mobility, 20-fold or greater dilution yielding the same results as for serum catalase. Similarly, when serum catalase was diluted 20-fold or more with 60 mmol/L phosphate buffer, it migrated similarly to erythrocyte catalase. I detected no effect of dialyzable serum ligands, NADPH, or protection of SH groups on the electrophoretic mobility of either catalase isoform. I conclude that formation of charge isoforms of catalase is caused by a reversible, conformational modification due to matrix effect of serum.