ABSTRACT
Enzymes are present in cells at much higher concentrations than in plasma. Some occur predominantly in cells of certain tissues, where they may be located in different cellular compartments such as the cytoplasm or the mitochondria. ‘Normal’ plasma enzyme concentrations reflect the balance between the rate of synthesis and release into plasma during cell turnover, and the rate of clearance from the circulation. Plasma enzyme levels depend on the extent of cell damage and the rate of release from damaged cells. Plasma amylase activity may be high as a result of renal glomerular impairment rather than pancreatic damage. Plasma Asparate aminotransferase activity is moderately higher during the neonatal period than in adults. Plasma Creatine kinase (CK) activity is higher in black people and Afro-Caribbeans than in white people. Plasma CK activity is raised in all types of muscular dystrophy, but not usually in neurogenic muscle diseases such as poliomyelitis, myasthenia gravis, multiple sclerosis or Parkinson’s disease.
