Post Synthetic Modification of CK-MM by Kininase I

Abstract

Cystolic creatine kinase (CK, EC 2.7.3.2.) is a dimeric enzyme exhibiting 3 isoenzymes : CK-MM, CK-MB and CK-BB. The CK-MM isoenzymes released in the serum during muscular damage and myocardial infarction. We have demonstrated that CK-MM isolated from human serum expresses multiple forms (Wevers et al., 1977) as a result of a post-modification of the M subunit. The cause of formation of these iso-forms was shown to be a removal of C-terminal lysine from both subunits (Yasmineh et al., 1981; Falter et al., 1981). Already, some investigators purified the enzyme responsible for this post-transl ational modification and determined its characteristics (Edwards and Watts, 1984; Perryman et al., 1984; Van Landeghem et al., 1985). Several names were given to this as yet unknown protein : CK conversion factor (Falter et al., 1981), modifying protein (Van Landegnem et al., 1985) and carboxypeptidase K (Edwards and Watts, 1984).