Abnormal activity of cellular enzymes

Introduction In normal people, the enzyme activity is relatively stable. The change of enzyme activity indicates that some organs and tissues of the human body are damaged or disease occurs, and some enzymes are released into blood, urine or body fluid. Therefore, by means of blood, urine or body fluid enzymes Activity determination, can understand or determine the occurrence and development of certain diseases.

Cause

In acute pancreatitis, amylase activity in serum and urine is significantly increased.

Hepatitis and other causes of liver damage, hepatocyte necrosis or permeability enhancement, a large number of transaminase released into the blood, so that serum transaminase increased.

Serum lactate dehydrogenase and phosphocreatine kinase were significantly elevated during myocardial infarction.

When organophosphorus pesticides are poisoned, cholinesterase activity is inhibited and serum cholinesterase activity is decreased.

Some liver and gallbladder diseases, especially biliary obstruction, serum r-glutamyltransferase increased and so on.

When the cells are aging, there will be a series of changes such as water reduction, accumulation of senile pigment-lipid pigment, decrease of enzyme activity, and slowing of metabolic rate.

an examination

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The activity of NADH-MetHb reductase was determined by using cyanmethemoglobin as a substrate, or the activity of diaphorase was determined by using dichlorophenol indophenol as a substrate, or b5R activity was determined by using cytochrome b5 as a substrate. It should be emphasized that the results of the assays in the test tubes (at high substrate concentrations) do not accurately reflect the extent of catalytic efficiency reduction in living cells (at low substrate concentrations) due to the different mechanisms of action of the different genetic variants. Because, if the molecular structure of the enzyme changes its affinity with the substrate NADH (Km value increases), under physiological conditions, the concentration of NADH in the cell is very low, and the enzyme activity is almost completely lost; but the enzyme activity is measured in a test tube. At the time, the added NADH is equivalent to several tens of times or even hundreds of times the physiological concentration, and the activity of the enzyme can be completely measured. If the enzyme activity is measured at a low substrate concentration, the instantaneous initial velocity must be recorded with a time scan, otherwise the error is too large. Other genetic enzyme deficiency diseases have similar problems.

Differential diagnosis

Differential diagnosis of abnormal cell enzyme activity:

1. Cytochrome C oxidase deficiency: Cytochrome C oxidase deficiency is a type of Fanconi syndrome. Fanconi syndrome is a hereditary or acquired disease. Often with cystine Accompanied by disease, characterized by abnormal proximal tubular function, causing glucoseuria, phosphate urine, amino aciduria and bicarbonate urine.

2, serum alkaline phosphatase activity increased: alkaline phosphatase (ALP) is a commonly used indicator for the diagnosis of biliary system diseases. Alkaline phosphatase is present in various tissues of the body and contains more bone, liver and kidney. Alkaline phosphatase in normal serum is mainly derived from bone, produced by osteoblasts, and excreted from the biliary system via the blood to the liver. This enzyme is significantly elevated in patients with cholestatic hepatitis and extrahepatic obstruction. ALP can only suggest biliary obstructive lesions, and it is not possible to identify whether the obstruction is benign or malignant.

3, pancreatic enzyme secretion or discharge decreased: chronic pancreatitis (chronic pancreatitis) is due to various factors caused by persistent and permanent damage to pancreatic tissue and function. Different degrees of acinar atrophy, pancreatic duct deformation, fibrosis and calcification in the pancreas, and varying degrees of pancreatic exocrine and endocrine dysfunction, clinical manifestations of abdominal pain, diarrhea or steatorrhea, weight loss and malnutrition and other pancreatic insufficiency Symptoms. In chronic pancreatitis, the amount of pancreatic juice, sodium bicarbonate, and various pancreatic enzyme secretions or excretions are reduced. Typical chronic pancreatitis is rare in China, and it is difficult to diagnose.

The activity of NADH-MetHb reductase was determined by using cyanmethemoglobin as a substrate, or the activity of diaphorase was determined by using dichlorophenol indophenol as a substrate, or b5R activity was determined by using cytochrome b5 as a substrate. It should be emphasized that the results of the assays in the test tubes (at high substrate concentrations) do not accurately reflect the extent of catalytic efficiency reduction in living cells (at low substrate concentrations) due to the different mechanisms of action of the different genetic variants. Because, if the molecular structure of the enzyme changes its affinity with the substrate NADH (Km value increases), under physiological conditions, the concentration of NADH in the cell is very low, and the enzyme activity is almost completely lost; but the enzyme activity is measured in a test tube. At the time, the added NADH is equivalent to several tens of times or even hundreds of times the physiological concentration, and the activity of the enzyme can be completely measured. If the enzyme activity is measured at a low substrate concentration, the instantaneous initial velocity must be recorded with a time scan, otherwise the error is too large. Other genetic enzyme deficiency diseases have similar problems.

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