CK catalyzes the reversible phosphorylation of creatine by ATP to form ADP and phosphocreatine, the major storage form of high energy phosphate in muscle. CK (in blood) is assayed as a marker of myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), muscular dystrophy, acute renal failure, and additional complications. Cayman's Creatine Kinase Fluorometric Assay provides a convenient method for detecting total CK activity in plasma and serum. CK catalyzes the reversible reaction between creatine phosphate and ADP to form creatine and ATP. Through a series of enzyme-coupled reactions, formaldehyde is generated. The cyclization of formaldehyde and acetoacetanilide in the presence of ammonia results in a fluorescent product which is analyzed using an excitation wavelength of 365-375 nm and an emission wavelength of 465-475 nm.