Various Enzymes and Their Clinical Significance

Enzymes are substances that catalyze biochemical reactions. Although they actively participate in the reaction, they are not changed in the process. They are almost always found in cells so any increase in their blood levels would indicate cellular destruction. These are important clinical enzymes which are measured in clinical chemistry to determine the presence or absence of a pathologic conditions.

1. Acid phosphatase (ACP) is primarily present in red blood cells (RBC), breast milk, and semen. It is tested to determine the occurrence of prostate cancer, breast cancer and some red blood cell pathologic conditions.

It is also used as a diagnostic tool in cases of rape. Since ACP is present in the semen, testing the vaginal fluid for the presence of ACP will indicate that the act has been committed.

2. Alkaline phosphatase (ALP) is found in bones, kidneys, liver, placenta, intestines and platelets. Elevated ALP levels would indicate bone and liver diseases like osteomalacia, liver cirrhosis, and the like.

3. Creatine phosphokinase (CPK) is found in the brain, heart, and muscles. It has three isoenzymes: CKBB (CK1), which is present in the brain, the CKMB (CK2), which is present in the heart, and CKMM (CK3), which is present in muscles. The significance of elevated results therefore are diseases related to the heart, brain and muscles.

4. Lactate dehydrogenase (LDH) is nicknamed the “ubiquitous enzyme” because it is almost present in all cells in the body. It is found in red blood cells, cardiac muscles, liver, lungs, spleen and kidneys. There are five isoenzymes: LDHHHH (LD1), LDHHHM (LD2), LDHHMM (LD3), LDHMMM (LD4), and LDMMMM (LD5). It is elevated in liver diseases and heart conditions like myocardial infarction (MI).

5. Gamma Glutamyl Transferase (GGT) is an alcoholic marker. Its elevation indicates liver disease and chronic alcoholism. It is only elevated after prolonged usage of alcohol.

6. Alanine amino transferase (ALT) is a liver enzyme. It is markedly elevated in liver disease.

7. Aspartate amino transferase (AST) is a cardiac enzyme. It is significantly elevated in myocardial infarction, and slightly elevated in liver disease. CK, LDH, and AST are the three cardiac enzymes.

These enzymes are important diagnostic markers of diseases. Do not disregard normal results. Serial measurements should be made on another sample, from the same person to ensure consistent results.

Before conclusive diagnosis is made, all data, like patient’s history, physical symptoms and other laboratory results should be integrated.



. by Allan Wu