CPK enzyme

CPK enzyme ( Also known as creatine kinase and creatine phosphokinase) present in almost all the body tissues in different amounts. It is very abundant in muscle cells and brain. CPK enzyme is responsible for the interconversion of creatine and creatine phosphate while consuming ATP as the substrate. This enzyme has tissue specific isoforms and because of that it has a great therapeutic value. For an example skeletal muscle fibers have CPK-MM isoform of the CPK enzyme. Brain has CPK-BB isoform.
Myocardial cells have CPK-MB isoform. When there is an damage to the cells CPK enzyme which is usually present within the cells comes out and present in the plasma. In any normal human there is a basal level of this enzyme in the plasma due to the normal wear and tear of the cells. But in the disease condition this level rise to a higher value due to the tissue necrosis associated with that disease. For an example in a myocardial infarction CPK enzyme level in the blood rise to a very higher level. Since it has a cardiac specific isoform(CPK-MB) this can be used to detect myocardial cell damage. But it is necessary to keep in mind that the CPK enzyme level can be elevated in various diseases affecting the skeletal muscles also. Few years back this enzyme was widely used to to detect myocardial infarctions but in the recent years it's place has been replaced by Troponin-T (another cardiac specific protein)