The body performs myriad chemical reactions in order to support itself. Many of the chemical reactions are assisted by enzymes. An enzyme is a type of protein that acts like a machine to change the structure of molecules. Some tissue types have a high concentration of a particular type of enzyme compared to other tissues. Certain disorders can lead to changes in the concentration of serum enzymes, serum being the liquid component of blood.
Serum Enzymes
Serum enzymes may be found normally in the serum. For example, the liver secretes a number of enzymes directly into the blood stream. Some of these help to fight off invading organisms, others help with blood clotting, among other functions. Tissue damage can cause cells to break apart, releasing enzymes into the blood that are normally found inside the cells. This can be measured through a blood test as an indicator of disease.
Commonly Measured Enzymes
There are many commonly measured enzymes on a blood panel. For example, if a person goes to a hospital with chest pain that is suspicious for a heart attack, a number of tests are performed, including a physical exam, an EKG and serum enzymes specific for the heart. Enzymes are used to help determine if there has been damage to the heart, liver, bones, bile ducts and other structures.
Indicators
Tissue damage can release enzymes. A heart attack is usually caused by the obstruction of a blood vessel feeding the heart. This cuts of the blood supply downstream from the obstruction, depriving an area of the heart of blood and oxygen. After a short time, the cells will break open and release enzymes. Blood levels of enzymes such as troponin I, CK-MB and LDH will rise. Similarly, in liver damage, levels of AST and ALT will rise. As the liver damage continues, scar tissue replaces the normal liver cells. Once most of the liver is replaced by scar tissue, the level of enzymes will drop.
Diagnosis and Treatment
The pattern of serum enzymes can be very helpful to both help diagnose and track the course of a disease. Increases or decreases from normal can help to establish a pattern for the disorder. While the enzymes can help to diagnose a problem, they must be treated as an indicator only. In other words, the enzymes themselves are not a disease and they are not treated. The underlying condition is treated, and the serum enzymes will adjust accordingly.
References
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar, et al.; 8th Ed 2009
- "Henry's Clinical Diagnosis and Management by Laboratory Methods"; Richard A. McPherson, et al.; 21st Ed 2006
