From Big Medical Encyclopedia

ENOLAZA (synonym of an enolaz) — 2-fos-fo-B-glitserat hydrolyase (phospho-pyruvate-hydratase, 2-fosfoglitse-rat-dehydratase; KF, enzyme of a class LiAZ catalyzing a reversible test of degidratirovaniye 2-fosfo-V-glitserata (2-phospho-glitserata, 2-phosphoglyceric acid) with formation of fosfoyenol-pyruvate (fosfoyenolpirovinograd-ache acids, an enolpiruvatfosfata).

This reaction leading to formation of makroergichesky connection — a fosfoyenolpiruvat from poor in energy 2 phosphoglycerates (see Vysokoergichesky connections), is an important stage of a glycoclastic way of splitting of carbohydrates (see Glycolysis). The reaction catalyzed E., serine - isocitrate - whether - aznogo ways of education atsetil-KOA from formaldehyde and C02 carbon dioxide at metilotrofny microorganisms represents also one of stages.

AA. it is extremely eurysynusic in the nature. At animals and the person E. it is most active in skeletal muscles and is less active in kidneys and a liver. Considerable eno-lazny activity is found in blood serum.

AA., allocated from various sources (including from yeast, muscles of the person and animals), it is received in crystalline state. Active molecules of enzyme have a pier. the weight (weight) 82 000 — 100 000 also consist of two identical subunits (monomers) about a pier. weighing 41 000 — 50 000. Monomers E. have no enzymatic activity. At nek-ry animal species existence of multiple forms eno-manholes is established (see Isoenzymes).

In c. N of page of the person and animals the specific neural form E is found., identical to so-called mozgspetsifichesky protein 14-3-2. In total three enzymes having E. V activity a brain of the adult a neural form E are found in a brain. not neural form E is localized only in neurons, and. — in a glia. At early stages of ontogenesis neurons contain hl in an unripe brain. obr. not neural form of an enolaza, edge in the course of differentiation it is replaced with neural enolazy.

AA. is the highly specific enzyme operating selectively on 2-fosfo-V-glitserat (in forward reaction) and fosfoyenolpiru-vat (in back reaction). Optimum of pH for E. is in neutral area of pH values and depends by nature buffer solution used at a research. For action E. presence of bivalent cations — Mg2 + is absolutely necessary or Mp2+, to-rye much change conformation (see) molecules of enzyme, stabilizing its active dimeric form. The ions of metal which are strongly connected to a molecule of enzyme participate in binding E. with substrate and probably in the subsequent electronic reorganizations. Inhibitors E. ions of fluorine F” (in the presence of ions of Mg2 + and phosphate), and also a pyrophosphate and ions of Sa2+ are. Addition of fluoride to the glycolyseing system stops enolazny reaction and leads to accumulation neprevra-shchenny phosphoglyceric to - t.

The reaction catalyzed E., consists in eliminating of water (totally) from the 2nd and 3rd carbon atoms 2-fosfo of of l of an itserat:

During this reaction water is released in the form of consistently leaving a hydrogen ion (a bystry stage) and a hydroxylic ion (a slow stage); intermediate compound (intermediaty) of this process is carbanion. Enolazny reaction can also be considered as intramolecular okislitelno - recovery process (see Redoxreactions), in Krom the oxidation level of the 2nd carbon atom 2 of phosphoglycerate increases, and the 3rd carbon atom — decreases. Considerable redistribution of intramolecular energy results, and phosphoradio communication poor in energy 2 phosphoglycerates turns into energy-rich enolfosfatny bond.

Activity E. determine by increase in concentration of a fosfoyenolpiruvat in forward reaction. Definition of a fosfoyenolpiruvat is carried out by yodometrichesk (see. Titrimetric analysis), on release of labile phosphatic group at acid hydrolysis (see Phosphorus, methods of definition) or (most often) spektrofotometrichesk (see Spektrofotometriya) on absorption at 240 nanometers (absorption 2 phosphoglycerates in this area is minimum). Activity E. define also in the interfaced fermental system taking into account transformation of a fosfoyenolpiruvat into pyruvate under the influence of a pyruvatekinase (KF, measure amount of the formed pyruvate in presence of l of the act of t dehydrogenase (see) and NAD-N on absorption recovered OVER at 340 nanometers.

Increase in activity E. it is revealed in blood serum of patients with a myocardial infarction, at diseases of a liver and innidiation of malignant tumors.

Bibliography: Vilkinson D. The principles and methods of diagnostic enzymology, the lane with English, M., 1981; D and to with about N M. and Webb E. Enzymes, the lane with English, t. 1 — 3, M., 1982; Handbook of neurochemistry, ed. by A. Lajtha, v. 4, p. 403, N. Y. — L., 1983. H. V. Gulyaeva.