Abstract
Creatine kinase (CK, EC 2.7.3.2) has a important role in muscle contraction and is rich in muscle tissue. The CK has three isoenzymes, designated as CK-MM (also termed CK3), CK-MB (CK2) and CK-BB (CK1). These isoenzymes are clearly separated by an electrophoresis. Myocardium contains significant quantities of CK-MB. Demonstration of elevated levels of CK-MB is considered the most specific indicator of acute myocardial infarction (AMI). CK-MM is resolved into three isoforms (MM1, MM2, MM3) by prolonged electrophoresis. The CK-MM3 in myocardium is released into blood and changes to CK-MM2, then CK-MM1 post-translationally. The detection of an elevated percentage of CK-MM3 in serum of patients with AMI indicates only a relatively recent myocardial injury like a myoglobin. In recent years, the unusual CK isoenzyme bands displaying electrophoretic properties that differ from the major isoenzyme fractions were observed. These atypical forms are generally of two types and are referred to as CK-linked immunoglobulin and mitochondrial CK (CK-m). The CK-m is detected in serum of extensive tissue damage, causing breakdown of the mitochondria.
