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enzymes
Biochemical catalysts, the majority of which are globular proteins although some, known as ribozymes, are composed of RNA. About 1,000 different varieties are found in the human body.
Enzymes facilitate key processes in the biochemistry of organisms which, otherwise, would take place too slowly for the maintenance of life. Enzymes speed up chemical reactions of substrates by lowering the activation energy. They have complex tertiary structures which are held in shape by weak chemical bonds between the polypeptide chains.
Each enzyme has a specific surface configuration with one or more clefts known as active sites to which only certain substrates can bind. Each enzyme is highly specific to the reaction it catalyzes as the substrate must fit precisely into the active site. If the active site loses its unique shape, it can no longer provide a point of attachment for its substrate and the enzyme is said to be denatured. This can happen if the enzyme is subjected to temperatures or pH levels outside of the narrow range in which it normally operates. Many enzymes require the assistance of certain accessory substances, known as cofactors and coenzymes, to function properly.
Related category
• BIOCHEMISTRY
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