Creatine kinase (CK) — also known as creatine phosphokinase (CPK) or phospho-creatine kinase — is an enzyme (EC2.7.3.2) expressed by various tissues and cell types. CK catalyses the conversion of creatine and utilizes adenosine triphosphate (ATP) to create phosphocreatine (PCr) and adenosine diphosphate (ADP). This CK enzyme reaction is reversible and thus ATP can be generated from PCr and ADP.