enzyme (rus. фермент) — Protein molecules, more rarely RNA molecules or their complexes, which accelerate (catalyse) chemical reactions in living systems.

Description

Enzymes are present in all living cells and contribute to the conversion of molecules (substrates) into different molecules (products). The main functions of enzymes are to catalyse the transformation of substances that enter the body or result from metabolism, and to promote biomolecular processes (such as genetic information reproduction and implementation). Enzymes act as catalysts in practically all biochemical reactions occurring in living organisms: they catalyse about 4,000 reactions. By their mechanism of action, enzymes can be devided to oxidoreductases (catalysing redox reactions), transferases (catalysing the transfer of a functional group from one molecule to another), hydrolases (catalysing the hydrolysis), lyases (catalysing the breaking of chemical bonds by means other than hydrolysis), isomerases (catalysing the isomerisation, such as racemases), ligases (involved in the catalytic synthesis of molecules, for example, ligation of double-stranded DNA fragments, which is coupled with ATP hydrolysis). A distinctive feature of the enzymes as compared with non-protein catalysts is their high specificity - binding constant of some enzyme-substrate complexes can be as high as 1010 l/mol or more. The enzyme specificity and activity are determined by their three-dimensional structure and achieved through a partial complementarity of charge and hydrophobic residue distribution on the substrate molecule and at the binding site of the enzyme. Furthermore, the efficiency of enzymes is much higher than the efficiency of non-protein catalysts: enzymes accelerate reactions by millions and billions of times, whereas non-protein catalysts - by hundreds or thousands of times. Many enzymes perform a catalytic function without any additional components. However, there are enzymes that require non-protein cofactors for catalysis. Cofactors can be both inorganic molecules (metal ions, iron-sulphur clusters, etc.) or organic molecules (such as flavin or heme). Organic cofactors, tightly bound to the enzyme, are called prosthetic groups. Organic сofactors which can easily detach from the enzyme, are called coenzymes. After synthesis many enzymes undergo modifications necessary for their full activity. Such modifications are called post-translational (processing). It is one of the levels of intracellular control of enzymatic activity. Enzymes are involved in all vital functions of living organisms, so it is not surprising that they are widely used in the food and textile industries, pharmaceuticals, and biotechnology. Many commercial enzymes are produced by biotechnology using bacteria or fungi hyperproducer strains, derived both by conventional selection or gene engineering.

Authors

  • Naroditsky Boris S.
  • Shirinsky Vladimir P.
  • Nesterenko Lyudmila N.

Sources

  1. Alberts B., Johnson A., Lewis J. et al. Molecular Biology of the Cell. 4th ed. — N.Y.: Garland Publishing, 2002. — 265 p.
  2. B. Glick, J. Pasternak. Molecular Biotechnology: Principles and Applications of Recombinant DNA. — 3rd ed. Sigma Publishing, 2003, 784 pp.
  3. R. Murray, D. Grenner, P. Meyes, B. Roduell. Biochemistry of the human (in Russian). / ed. by L. M. Ginodman. - М.: Mir, 1993. Enzyme // Chemical encyclopedia (in Russian). V. 5. — Moscow: Bol'shaja Rossijjskaja ehnciklopedija, 1998. 83-84 pp.
  4. Enzyme // Wikipedia, the free encyclopedia. — http://en.wikipedia.org/wiki/Enzyme (reference date: 12.10.2009).

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