Alcohol dehydrogenase is abundant in human and animal liver, plant and microbial cells. It is a zinc-containing metalloenzyme with broad substrate specificity. Alcohol dehydrogenase can use nicotinamide adenine dinucleotide (NAD) as a coenzyme to catalyze the reversible reaction between primary alcohols and aldehydes: CH3CH2OH+ NAD+→ CH3CHO +NADH+ H+.

In humans and mammals, alcohol dehydrogenase and aldehyde dehydrogenase (ALDH) constitute the alcohol dehydrogenase system, which is involved in ethanol metabolism in vivo and is an important metabolic enzyme in humans and animals. As a key enzyme in the metabolism of major short-chain alcohols in organisms, it plays an important role in many physiological processes. It is a broad-specific zinc-containing metalloenzyme. The alcohol dehydrogenase alcohol oxidation system is a major pathway for the metabolism of alcohol in the liver. The alcohol dehydrogenase oxidation system includes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH).

Alcohol dehydrogenase is a dimer with a mass of 80 kDa and includes a group of isozymes, all of which are capable of converting ethanol to acetaldehyde. In mammals, this is a redox reaction involving the coenzyme nicotinamide adenine dinucleotide (NAD+). Alcohol dehydrogenase is responsible for catalyzing the oxidation of primary and secondary alcohols to aldehydes and ketones, and can also affect their reverse reactions. However, for primary alcohols, this catalytic effect is not strong, while the catalytic effect is stronger in secondary alcohols and cyclic alcohols. The optimum pH value of alcohol dehydrogenase is between 7.0 and 10.0. The enzyme activity reaches the maximum when the pH value is 8.0, and the enzyme activity is relatively stable when the pH value is 7.0. The optimum temperature for the action of ADH was 37°C. The enzyme activity was relatively stable when the temperature was 30-40°C, and the enzyme activity decreased sharply when the temperature exceeded 45°C.

Application of Alcohol Dehydrogenase
1. Disease diagnosis
ADH in the human body is mainly produced in the liver, so liver disease may be related to serum ADH activity. Determination of ADH activity in serum by spectrophotometry and combined with clinical investigation of this index are of great significance in the diagnosis of liver diseases. Serum ADH activity was measured experimentally to reflect whether the liver function was normal. The results of the determination of ADH in the serum of liver patients were significantly higher than the reference value of healthy people.

2. Alcohol concentration
In daily social life, people are inevitably exposed to alcohol. Traffic accidents caused by drunk driving are not uncommon. In addition, excessive drinking can cause alcohol poisoning. In view of the serious consequences of drinking accidents and alcoholism, the rapid determination of ethanol concentration in plasma has very important clinical value for preventing accidents and early diagnosis and treatment of acute alcoholism.

There is a new method for the determination of ethanol concentration in plasma by enzymatic end-point method, which does not require protein removal, and the entire detection process takes only 90 seconds. It can be used in automatic biochemical analyzers and manual operations, and is suitable for routine clinical use. In the experiment, the scientists chose tris (hydroxymethyl) aminomethane-hydrochloric acid (Tris-HCL) as the buffer system. Under alkaline conditions, alcohol dehydrogenase (ADH) catalyzes the conversion of ethanol to acetaldehyde, and simultaneously generates reduced coenzyme (NADH). Changes in absorbance were detected at a wavelength of 340 nm, and the concentration of ethanol was calculated against the standard.

3. Alcoholism
Studies have shown that alcohol dehydrogenase may lead to alcohol metabolism-dependent alcoholism in patients. The researchers initially detected several genes that may be associated with alcoholism. If the ADH2 and ADH3 encoded by these gene variants enter slow metabolizing forms, it may increase the risk of alcoholism. The study found that mutated ADH2 and ADH3 are associated with alcoholism in Asian populations, but whether this is the case needs to be further studied.

4. Drug dependence
Drug dependence is another problem with alcohol dehydrogenase, which researchers believe may be related to alcoholism. A particular study showed that drug dependence was associated with seven alcohol dehydrogenase-related genes. These results may aid in targeted treatments for these specific genes, which awaits more in-depth research.

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