From Big Medical Encyclopedia

PHOSPHORYLATION — process of inclusion of the rest of mineral phosphoric acid in molecules of various chemical compounds. In zooblasts, plants and microorganisms F. plays an important role in a metabolism and energy (see).

Reactions F., the ATP which are followed by education at glycolysis (see) and in a cycle tricarboxylic to - t (see. Tricarboxylic acids a cycle), call substrate F. unlike oxidizing F., proceeding in a respiratory chain (see biological oxidation), or a fotofosforili-rovaniye at photosynthesis (see).

Reactions F. are connected with the most various functions of a cell: mechanical, osmotic and transport, and also effect of hormones (see), neutralization of toxic metabolic products and removal from an organism of final metabolites, light adaptation of a visual cell (see Rhodopsins), etc. Special value of reaction F. have for synthesis of nucleic acids (see) and proteins (see). Effect of DNA - and RNA polymerases is connected with phosphorylation (see Polymerases).

More than 25 enzymes and large numbers of not fermental proteins, functional activity are known to-rykh it is regulated by F. p dephosphorylations. The nervous and hormonal regulation of activity of enzymes (see) connected with phosphorylation — dephosphorylation, plays an essential role at muscular contraction (see), secretions (see), transmembrane transfer of substances (ShM. Membranes biological), transport of ions (see), growth and a differentiation of fabrics, synthesis and the proteolysis, carbohydrates and fats.

T. and dephosphorylation regulate activity of biomolecules, doing possible their inclusion in recyclings or bringing them out of an active metabolism of substances.

In reactions F. the enzymes catalyzing transfer of various groups on free inorganic phosphate participate. It is a transfer elements (see) and the enzymes catalyzing transfer of the phosphatic rest on low-molecular weight compounds and proteins — phosphotransferases (see). Mineral phosphate turns into biologically active compounds under the influence of phosphorylases. Products of a phosphorolysis (see) and a pirofosforo-liza are used for synthesis of high-energy connections (see. Vy-sokoergichesky connections) and at various stages of synthesis of polysaccharides (see), phospholipids (see Phosphatides), nucleosides, nucleotides and other substances. The reactions proceeding as a phosphorolysis and a pyro-phosphorolysis are reversible. Fosfotrans-feraznye reactions, in to-rykh the donor of the phosphatic rest serve ATP or other nukleozidtrifosfata proceeding with energy consumption are almost irreversible. Acceptors of the ^-phosphatic rest of ATP are the connections containing spirit group (sugar, their derivatives, glycerin, sincaline, nek-ry mines of Vit), a carboxyl group (acetate, aspartate, etc.) or an amino group (creatine, arginine, etc.). ATP participates in F. nukleozidmono-and nukleo-ziddifosfat, and also in reactions of transfer of a pyrophosphate and phosphate, in processes of synthesis of coenzymes (see).

Synthesis of protein begins with F., providing activation of amino acids at formation of aminoatsilade-nilat (see Proteins, biosynthesis of protein). At the following stages of synthesis of protein F. to participation of a guanozintrifosfat (GTF) there is in the course of accession an aminoacyl-TRNK to a ribosomal complex and during the movement peptidil-TRNK from aminoacylic to the peptidilny site of a ribosome (see).

The electronic and transport system of a respiratory chain and enzymes participating in oxidizing F., are localized on an inner membrane of mitochondrions (see) and are functionally connected among themselves. Certain points respiratory tsepp are accompanied by synthesis of ATP from ADF and the inorganic phosphate catalyzed by a difficult fermental complex — ATF-sintetazoy. In back reaction the same enzyme catalyzes hydrolysis of ATP. The phosphorylation connected with aerobic and anaerobic synthesis of ATP depends on the size of a ratio of ATF/ADF in a cell. At the high size of this relation braking of synthesis of ATP is observed.

Occurring at F. activation of a triglitseridlipaza (KF and Ying kt a willow a tion of of l and tse r about f wasps f oa c and l -

transferases (KF coordinates disintegration and synthesis of fats (see the Lipometabolism) in fatty tissue in response to intake of adrenaline (see). Activation of a holesterinesteraza (holesterolesteraza; KF phosphorylation causes increase in amount of the cholesterol (see) used for a steroidogenesis (see Corticosteroids) in bark of adrenal glands. Stimulation of a gluconeogenesis in a liver of glucagonomas (see) is carried out posredstvokhm an inactivation of a 6-fosfofrukto-2-kinase and a feast-vatkinazy (KF and activation of fruktozo-1,6-diphosphatase (KF 4.1.2. 13) as a result of phosphorylation

of these enzymes (see. Carbohydrate metabolism). Phosphorylation of a fenilala-ningidroksilaza (KF of a liver activates splitting of amino acids, increasing thereby education of gluconeogene predecessors and participants of a cycle trikarboyaovy to - t. At F. tyrosine hydroxyl elements (KF of adrenal glands and a brain activity of this enzyme raises also the speed of synthesis of hormones, adrenaline, noradrenaline (see) and dopamine (see Catecholamines) increases in response to stimulation of nerves. Phosphorylation of a kinase of light chains of a myosin (see. Muscular tissue) inactivates enzyme, blocking assembly of a myosin in filaments and manifestation ATF-aznoy of activity of actomyosin. Thanks to this mechanism the relaxation of unstriated muscles caused by adrenaline is mediated.

Regulation of many processes in an organism is carried out by F. and dephosphorylations of proteins under the influence of protein kinases (see Kinases) and proteinfosfataz (see Phosphatases). As a result of F. molecules atsetil-KOA — carboxymanholes (KF in several sites, catalyzed by different protein kinases, activity of enzyme decreases and thus control of synthesis of fatty acids is exercised (see) in fatty tissue — adrenaline and in a liver — glucagonomas.

Under the influence of protein kinases there is also F. ribosomal proteins and membrane proteins of subcellular organellas, napr, mitochondrions (see) that allows to carry out regulation of metabolic process on the signal received at linkng of the regulatory agent with membrane receptors. In a kernel there is F. proteins, however its functional role is established only in nek-ry cases. So, T. a histone of H1 (see Histones) is a signal to start a mitosis (see), and phosphorylation of a RNA polymerase of I leads to activation of this enzyme.

Among a large number of protein kinases interest is attracted by the so-called ti-rozinovy protein kinase allocated from a virus of sarcoma of Raus differing in high oncogenicity. It strenuously phosphorylates many cellular proteins, including the proteins responsible for a structure and growth of cells. Uncontrolled F. proteins leads to disturbance of their functions. Research F. proteins with a tumoral growth it is connected with a problem of chemotherapy of cancer.

Genetically caused loss of nek-ry processes F. is the reason of a serious hereditary illness. At muscular dystrophy are broken by F. creatine (see). Accumulation of abnormal quantities of a glycogen (see) in muscles and a liver is connected with hereditary diseases, at to-rykh is reduced or in general there is no activity of phosphorylases (see) in a liver and muscles (see Glycogenoses). Disturbance of exchange of a glycogen in a liver can be connected with insufficiency of glyukozo-6-phosphatase (KF At a galactosemia (see) in a liver the product F collects. galactoses (see the Galactose) — galaktozo-

1 phosphate having an inhibiting effect on other enzymes of glycolysis (see). Inborn hemolitic anemia is connected with insufficiency of enzymes F. — a hexokinase (KF and pyruvate kinase (see Enzimopenichesky anemia). Processes F. are broken also at hepatitis (see), hormonal frustration and other diseases.

Bibliography: Lenindger A. Biot

chemistry, the lane with English, page 391, etc., M., 1974; Moss D. U. and B and t of t e r-in about r t of Item D. Enzymology and medicine, the lane with English, M., 1978; The Cheekbone -

h e in V. P. and Kozlov I. A. Proton adenozintrifosfataza, M., 1977; Whyte A., etc. Fundamentals of biochemistry, the lane with English, M., 1981; Krebs E. G. a. Beavo J. A. Phosphorylation — dephosphorylation of enzymes, Ann. Rev. Biochem., v. 48, p. 923, 1979; Recently discovered systems of enzyme regulation by reversible phosphorylation, ed. by P. Cohen, Amsterdam — N. Y., 1980.

P.JI. Vulfson.