Enzyme

Enzymes are proteins that act as biological catalysts. Catalysts accelerate chemical reactions. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Study of enzymes is called enzymology and a new field of pseudoenzyme analysis has recently grown up.

About Enzyme in brief

Enzymes are proteins that act as biological catalysts. Catalysts accelerate chemical reactions. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. The study of enzymes is called enzymology and a new field of pseudoenzyme analysis has recently grown up. Some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual ‘pseudocatalytic’ properties. Enzymes known to catalyze more than 5,000 biochemical reaction types. Some household products use enzymes to speed up chemical reactions: enzymes in biological washing powders break down protein, starch or fat stains on clothes, and enzymes in meat tenderizer break down proteins into smaller molecules, making the meat easier to chew. The discovery that enzymes could be crystallized allowed their structures to be solved by x-ray crystallography. This was first done for lysozyme, an enzyme found in saliva and egg whites, and lysoase, found in tears and saliva. These three scientists were awarded the 1946 Nobel Prize in Chemistry for their work on the digestive enzymes pepsin and chymotrypsin. The biochemical identity of enzymes was still unknown in the early 1900s. James Sumner showed in 1926 that the enzyme urerease was a pure protein and crystallized it; he did likewise for the enzyme catalase in 1937. The word enzyme was used later to refer to nonliving substances such as pepin.

Louis Pasteur concluded that this fermentation was caused by a vital force contained within the yeast cells called ‘ferments’ which were thought to function only within living organisms. He named the enzyme that brought about the fermentation of sucrose ‘zymase’ in 1907. In 1907, he received the Nobel Prize for ‘his discovery of cell-free fermentation’. Following Buchner’s example, enzymes are usually named according to the reaction they carry out: the suffix -ase is combined with the name of the substrate or to the type of reaction. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, which comes from Greek ‘leavened’ or ‘in yeast’ to describe this process. French chemist Anselme Payen was the first to discover an enzyme, diastase, in 1833. In the late 17th and early 18th centuries, the digestion of meat by stomach secretions and the conversion of starch to sugars by plant extracts and saliva were known but the mechanisms by which these occurred had not been identified. By the late 1800s, enzymes were used commercially, for example, in the synthesis of antibiotics. Some enzyme activity can be affected by other molecules: inhibitors are molecules that decrease enzyme activity, and activators are molecule that increase activity. An enzyme’s activity decreases markedly outside its optimal temperature and pH, and many enzymes are denatured when exposed to excessive heat, losing their structure and catalytic properties.

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