Kinetic behaviour of human erythrocyte casein kinases. Effect of 2, 3-bisphosphoglycerate and heparin.

The predominant cAMP-independent casein kinase CS isolated from human erythrocyte hemolysate and membrane casein kinase MS are inhibited to the same extent by 2,3-bisphosphoglycerate (2,3-DPG). However, under some conditions, both enzymes may appear to be unaffected or even stimulated by this prominent red cell metabolite, depending on casein and monovalent salt (NaCl, KCl) concentrations employed in the assay. In addition, both casein kinases CS and MS exhibit identical response to heparin, being unaffected by increasing concentrations of this mucopolysaccharide up to 400 ng/ml. On the contrary, the minor cytosolic casein kinase CTS, is inhibited by both 2,3-DPG and heparin under all conditions tested in the assay.