Monoclonal antibody inhibiting creatine kinase MM3 but not isoform MM1.

Monoclonal antibody CKM-G01 inhibited greater than 99% of the activity of porcine and human creatine kinase(CK)-MM isoenzyme purified from muscle. However, it inhibited only 54% of CK-MM in human serum. Chromatofocusing of serum CK-MM showed that CKM-G01 inhibited 100% of MM3 but not isoform MM1. CKM-G01 inhibited CK-MM2 by 57%. CKM-G01 specifically inhibited only the original CK-M subunit and not the subunit modified by removal of C-terminal lysine by carboxypeptidase N. CKM-G01 can be used for assay of CK isoforms. We devised a new diagnostic reagent involving it, which requires no analytical separation of isoforms, based on the immunoinhibition method, and applied it to early diagnosis of acute myocardial infarction. The "inhibition index," (inhibited CK activity/total CK activity) x 100, increased more rapidly than did total CK and CK-MB. Evidently this diagnostic reagent can be used for easy, early diagnosis of acute myocardial infarction.