Serum enzyme tests have been used in clinical practice for a long time, such as increased amylase activity in serum and urine of patients with acute pancreatitis. In the 1930s, some scholars reported that the determination of serum lipase and alkaline phosphatase activities is helpful for the diagnosis of pancreatitis and bone diseases, respectively.
After the 1950s, the application of serum enzyme activity measurement as an indicator for monitoring cell and organ damage and tumor growth has expanded the scope of clinical chemistry tests. At present, diagnostic enzymology has been formed, which plays an extremely important role in disease diagnosis, curative effect observation and prognosis. . Studies have shown that, due to cell damage, enzymes in the cells are released from human blood, which accelerates the study of the causal relationship between disease and enzyme concentration in body fluids. At present, there are more than 100 kinds of enzymes for diagnostic use, of which more than 30 kinds of enzymes are widely used in clinical practice.
1 Characteristics and distribution of enzymes
As a biological catalyst, enzymes exist in serum, plasma, secretions and tissue fluids. Enzyme detection can be used for clinical diagnosis of chemical reactions that can occur with a small amount of enzymes at low activation energy. Enzymes are specific to reactions, and specific enzymes can catalyze specific chemical reactions. The characteristics of the enzyme determine the specificity of the corresponding substrate, and the enzyme can only convert a specific substrate or a group of substrates into a reaction product.
Serum enzymes come from tissues or secretions that enter the plasma, and tissue enzymes come from the metabolic processes of cells. Enzyme synthesis and secretion in normal tissues are enhanced. In the case of tissue damage, the activity of serum is increased. The reason is the increase in the number and activity of enzymes in tissue cells. The induction of enzymes increases the synthesis of enzymes in tissue cells. Hepatocytes increase GGT synthesis under the chemical stimulation of ethanol.
2 Significance of diagnostic enzyme testing
The determination of enzyme concentration in serum and other body fluids can provide clinicians with extremely diagnostic data. At present, the most commonly used method in clinical practice is the determination of enzyme activity. The absolute quantification method is to determine the content of enzyme protein or the concentration of enzyme molecules.
Diagnostic enzymology, that is, the detection of enzymes in serum or plasma, is mainly used to diagnose underlying diseases. The differential diagnosis of diseases in organs is the location of cell damage in the organs. Through enzyme activity detection, diagnostic evidence can be obtained from the enzyme activity level in the sample.
2.1 Tissue specific enzymes
These enzymes only appear in specific tissues or have very high activity in specific tissues. The increase of these enzymes in the serum indicates that certain tissues are damaged.
2.2 Enzyme form
The ratio of enzyme activity can provide clinical diagnostic information. The most basic enzymes in the form of enzymes are ALT and AST. More than 90% of the increase in enzymes is in important tissues such as liver, myocardium, skeletal muscle and red blood cells. The complement of isoenzymes in each tissue is determined by genes. Through the analysis of isozymes, we can clearly increase the origin of the tissue, such as amylase CK-MB, LD-1.
3 Enzyme levels and disease diagnosis
The mechanism by which enzymes are released into and cleared from the blood has a typical time curve. This time curve coincides with the characteristics of the enzyme activity time curve. These enzyme activity time curves provide a diagnostic time window for the clinic. Enzyme activity is expected to increase when the disease exists, and it can also be used to assess the stage of clinical disease.