blood enzyme activity level blood creatine kinase activity level true blood CPK activity level blood creatine phosphokinase activity level JSmith 2014-03-11T14:12:54Z blood CK activity level https://www.ncbi.nlm.nih.gov/pubmed/28288363 The amount of enzymatic activity of creatine kinase (CK) enzyme in a specified sample of blood. CK catalyses the reversible transfer of phosphate between ATP and various phosphogens such as creatine phosphate. Blood CK level is used as an enzymatic marker for myocardial infarction, rhabdomyolysis and acute renal failure.