CK-MB Type II possesses the naturally occurring carboxy-terminal amino acid lysine.This occurs during a myocardial infarct (MI or heart attack) when CK-MB Type II is released from damaged heart muscle, and the C-terminal lysine is cleaved in the blood stream, thus creating CK-MB Type I. This difference can be exploited in diagnosis of an MI Synonyms: Creatine Kinase MB Isoenzyme Type-II, CKMBITII, CKMBI, CKMB