blood enzyme activity level serum creatine kinase activity level 2014-03-11T14:14:26Z JSmith The amount of enzymatic activity of creatine kinase (CK) enzyme in a specified sample of serum. CK catalyses the reversible transfer of phosphate between ATP and various phosphogens such as creatine phosphate. Serum CK level is used as an enzymatic marker for myocardial infarction, rhabdomyolysis and acute renal failure. serum CK activity level serum CPK activity level serum creatine phosphokinase activity level