Encyclopedia of Family Health - Vol. 5

Encyclopedia of Family Health - Vol. 5

Encyclopedia of Family Health - Vol. 5

Encyclopedia of Family Health - Vol. 5

Excerpt

Enzymes are proteins that speed up reactions in the body. They are known as catalysts, and they make possible almost all of the body's vital processes, including digestion, growth, and reproduction.

Enzymes activate processes that create and sustain life. Here (inset), it is possible to see their action in a biological detergent, as the detergent digests a bloodstain.

Enzymes accelerate chemical reactions that allow any living organisms, including humans, to function normally. Enzymes speed up some chemical reactions several thousandfold. Thousands of varieties of enzymes are found throughout the body; each promotes a different chemical reaction. The majority of genes in our DNA genome function to provide the genetic code for the synthesis of enzymes. That process demonstrates the importance of enzymes in the functioning of the human body. Hereditary diseases are the result of gene mutations that cause defective enzymes. Each cell in the body makes the enzymes it needs to function. Some enzymes are so important that they are produced by every cell; they are usually used within the cell itself. Others are produced only by specialized cells; they may be secreted and used outside the cell. For example, enzymes involved in the digestive process act outside cells, in the gut itself. Some substances can deactivate enzymes by occupying their working areas. Cyanide has this effect on an enzyme called cytochrome oxidase, which is involved in the production of energy, and small quantities of cyanide can quickly cause death. Many disorders are caused by enzyme deficiencies. Albinos lack an enzyme called tyrosinase, which helps make the skin pigment melanin. Other enzymes convert the amino acid tyrosine to thyroid hormone: if one of the enzymes is missing at birth, the child will be mentally retarded. Enzyme deficiency disorders can be traced back to defects in genes. Problems can be alleviated if the missing enzyme is replaced.

Many prescribed drugs work by altering enzyme activity. Aspirin inhibits the activity of cyclooxygenase, an enzyme involved in producing prostaglandins, which are thought to cause painful inflammation of the joints (see Inflammation), so aspirin is a useful treatment for disorders such as rheumatoid arthritis.

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