Activation of enzymes in red blood cell membranes by a basic protein isolated from cobra venom

Abstract

Treatment of human red cell membranes with direct lytic factor, a basic protein isolated from cobra venom, resulted in a marked increase in glyceraldehyde 3-phosphate dehydrogenase (EC 1.2.1.12), adenylate kinase (EC 2.7.4.3), 3-phosphoglycerate kinase (EC 2.7.2.3.) and aldolase (EC 4.1.2.7.) activities, while catalase (EC 1.11.1.6) activity was not affected. Direct lytic factor had no effect on the enzyme activities when added to stroma-free hemolysate. With rising direct lytic factor concentration activation of glyceraldehyde 3-phosphate dehydrogenase in the membrane reached maximum value prior to elution of the enzyme from the membrane. Increasing direct lytic factor concentrations applied to red cell suspensions induced leakage of catalase and hemoglobin in a constant ratio, while glyceraldehyde 3-phosphate dehydrogenase leaked in an increasing ratio to hemoglobin. Other basic proteins such as bee-venom melittin, protamine and histone mimicked the direct lytic factor effect, thus pointing to the significance of the net positive charge of the protein molecule in the activation of the enzymes in the membrane. The data are consistent with the assumption that for the red cell enzymes glyceraldehyde 3-phosphate dehydrogenase, adenylate kinase, 3-phosphoglycerate kinase and aldolase, those parts which are associated with the isolated membranes are actual membrane components. For catalase the membrane-associated part is unspecifically adsorbed.