clinical enzymology

Clinical Enzymology (plasma enzyme in diagnosis) Most 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 levels reflect the balance between the rate of synthesis and release into plasma during cell turnover, and the rate of clearance from the circulation

The enzyme activity in plasma may be:
Increased due to proliferation of cells, an increase in the rate of cell turnover or damage or in enzyme synthesis (induction), or to reduced clearance from plasma.
Lower than normal, very occasionally due to reduced synthesis or congenital deficiency. Changes in plasma enzyme activities may sometimes help to detect and localize tissue cell damage or proliferation, or to monitor treatment and progress of disease.

Assessment of Cell Damage and Proliferation Plasma enzyme levels depend on:
1. The rate of release from damaged cells which, in turn, depends on the rate which damage is occurring:
2. The extent of cell damage. In the absence of cell damage the rate release depends on:
1. The rate of cell proliferation.
2. The degree of induction of enzyme synthesis
These factors are balanced by:
• The rate of enzyme clearance from circulation.

It is not known how most enzymes are removed from, or their action inhibited in the circulation.
Relatively small peptides, such as ?-amylase, can be cleared by the kidneys.
most enzymes are large proteins and are probably catabolized by plasma proteases before being taken up by the reticuloendothelial system.
In health each enzyme has a fairly constant and characteristic biological half-life; knowledge of this half-life may be of help in assessing the time since the onset of an acute illness.