CREATINE KINASE

From Big Medical Encyclopedia

CREATINE KINASE (ATP: kreatinfosfotransferaza; KF 2.7.3.2) — the enzyme relating to phosphotransferases; catalyzes reaction of reversible transfer of the fosforilny rest from ATP to creatine with formation of vysokoergichesky connection — creatine phosphate. Activity To. serves as additional diagnostic test at various diseases in blood serum.

Reaction product, catalyzed To. — creatine phosphate collects in fabrics, creating in them a stock of chemical energy which is used by cells at increase funkts, loadings (e.g., at reduction of muscles, at active transport of ions in nervous tissue, etc.). To. — the only enzyme catalyzing education and splitting of creatine phosphate plays an important role in maintenance of a ratio of ATP: ADF in a cell, influencing thereby processes of breath (see. biological oxidation ) and glycolysis (see). To. it is found in various tissues of vertebrate animals and the person and in some species of invertebrates (erinaceouses, chordates). In plants and microorganisms To. it is not found.

To. it is opened in 1932 by O. Meyergof and Lomann (To. Lohmann). In a crystal look To. for the first time received from skeletal muscles of a rabbit of S. A. Kuby, L. Noda and Lardi (N. A. Lardy) in 1954. To. it is activated by bivalent cations. The maximum speed of response depends by nature such cation and decreases among Mg 2+ > Mn 2+ > Ca 2+ . The reaction catalyzed To., it is reversible since it is followed by rather little change of free energy. The direction and speed of response to a large extent depend on the size pH. Forward reaction (phosphorylation of creatine) has an optimum of pH 9,0; back reaction (splitting of creatine phosphate) — pH 7,0.

The size of enzymatic activity To. depends from funkts, conditions of body or fabric. Activity To. in muscles with different function changes among: cross-striped muscles> of a muscle of heart> of a muscle of a pregnant uterus> of a muscle of a uterus> unstriated muscles. In different departments of a brain and heart activity To. it is not identical. In blood serum of the person traces of activity of K. V erythrocytes normal are defined this enzyme is practically absent. To. it is characterized by presence of several isoenzymes (see). In a human body and animals two polypeptide chains (M - and B-type) are synthesized from which three isoenzymes are combined To.: The I (VV), II (MB), III (MM) having relative fabric specificity. The isoenzyme of III is specific to white skeletal muscles, an isoenzyme of I — to a brain. Heart and red skeletal muscles along with isoenzymes of I and III contain a hybrid isoenzyme of II. In kidneys and unstriated muscles the isoenzyme of I is found. Pier. the weight (weight) of all three isoenzymes are almost identical (81 000 — 83 000), however their electrophoretic mobility, the amino-acid structure and antigenic properties are various. In the course of an embryogenesis of animals and the person there is an increase of activity To. and change of its isofermental range.

In the 60th 20 century, in addition to three cytoplasmatic isoenzymes To., forms K were found., connected with membranes of various intracellular structures: mitochondrions, sarcoplasmic reticulum, kernels. Falls to the share of mitochondrions in a skeletal muscle apprx. 7%, in a cardiac muscle — apprx. 30 — 40%, in a brain — apprx. 10 — 20%, all activity To. in a cell. Mitochondrial form K. it is extremely important for metabolism of a cardiac muscle since it transfers a considerable part of the ATP vysokoergichesky phosphate which is formed in mitochondrions to creatine; the creatine phosphate which is formed at the same time together with To. cytoplasms is considered as system of transport of vysokoergichesky phosphate from mitochondrions to myofibrils and other places of utilization of energy in a cordial cell.

Activity To. it was valuable diagnostic test at acute disorders of metabolism of a myocardium, especially at myocardial infarction (see). At an acute myocardial infarction increase in activity To. occurs in 3 — 4 hours after the beginning of a disease, and the maximum activity of enzyme (norms are 5 — 20 times higher) is noted by the end of the first days. In blood serum of the patient the maintenance of MM - and MV isoenzyme considerably increases To. On 2 — the 3rd days later there began diseases activity To. is returned to norm. Definition of activity To. is the most informative biochemical, the test at diagnosis of a myocardial infarction. At hereditary muscular dystrophy like Dyushenn (see. Myopathy ) increase in activity is observed To. in blood serum by 15 — 50 times; at the same time in muscles there are MB - and the VV-isoenzymes which are absent at healthy people, and the general activity To. in muscles decreases.

In clinic activity To. in blood serum determine by Müller's method — Vollenbergera — Kovarikova. By this method of creatine phosphate formed in forward reaction of phosphorylation of creatine, determine after acid hydrolysis by mineral (inorganic) phosphorus by a colorimetric method. At the course of reaction in the opposite direction the formed creatine is determined colorimetric with alpha-naphthol and diacetyl by Ennor's method — Rosenberg or flyuorimetrichesk with ninhydrin.

Activity To. determine also by spectrophotometric methods, continuously registering the adeninenucleotides which are formed in the course of reaction (ATP or ADF). In forward reaction the formed ATP is determined by Oliver's method in the system interfaced to two additional enzymes — a hexokinase and glyukozo-6-fosfatdegid-rogenazoy. In back reaction the formed ADF is determined by Tantser's method — Gilvarga in the system interfaced to a pyruvatekinase and a lactate dehydrogenase (see. Creatine ).

Isoenzymes To. define electrophoretic and immunochemical, methods.

See also Fosfotransferaza .



Bibliography: Biochemical methods of a research in clinic, under the editorship of A. A. Pokrovsky, page 128, M., 1969; Ivanov I. I., Korovkin B. F. and Markelov I. M. Introduction in clinical enzymologies), page 208, M., 1974; L y z l island and S. N. Fosfagenkinaza, L., 1974; Todorov Y. Clinical laboratory trials in pediatrics, the lane with bolg., page 896, Sofia, 1968; Chetverikova E. P. ATF-kreatinfosfotransfe-raza, distribution and properties, in book: Usp. biol, chemical, under the editorship of B. N. Stepanenko, t. 9, page 107, M., 1968, bibliogr.; R about-s and 1 k i S. Seeking the way, in book: Quality control clin, biochem., ed. by G. Anido a. o., p. 175, B. — N. Y., 1975, bibliogr.; Watts D. C. Creatine kinase, in book: The enzymes, ed. by P. D. Boyer, v. 8, p. 383, N. Y. — L., 1973, bibliogr.

L. V. Belousova.

Яндекс.Метрика