ENTEROTOXINS

From Big Medical Encyclopedia

ENTEROTOKSYNY (Greek enteron a gut + toxikon poison) — the polipep-tidny or proteinaceous factors of pathogenicity of bacteria possessing enterotropic action.

Knowledge of the nature and properties E. find application in medical practice for receiving specific serums, to-rye use for the purpose of indication and identification E. at epidemiol. the analysis of food toxicoinfections, and also for the emergency passive prevention and treatment of the enterit caused by the bacteria producing entero-toketsna.

On the nature of the striking action E. divide into two basic groups: AA., breaking secretory process in enterocytes; AA., breaking ability of enterocytes to soak up from a gleam of a gut nutrients (see Intestines), In the first group the thermostable factors of the polypeptide nature causing activation of guanylate cyclase distinguish (see. Guanylic acid) enterocytes, and the thermo labile proteinaceous factors activating adenylatecyclase (see Ada-nozinfosfornye of acid) enterocytes. Ability to development of the thermostable factors maintaining warming up at f 100 ° within 10 — 30 min. without loss of toxic activity is described at SAT-pilobacter of jejuni, S. by coli, S. fetus,

S. sputorum, Escherichia coli, Ed-wardsiella tarda, Klebsiella pneumoniae, Eaterobacter cloacae, Yersinia enterocolitica, Vibrio parahaemoly-ticus. The determinants coding synthesis of thermostable factors have plasmid localization and control synthesis of polypeptides from 18 — 33 and more amino-acid remains. In structure of these polypeptides it is revealed from 1 to 3 disulfide bridges. At nek-ry cultures (e.g., E. coli and Y. enterocolitica) at the final stages of synthesis from polypeptides dimeric and trimerous thermostable factors form. All thermostable factors intensively cosecrete microorganisms on Wednesday of cultivation and have similar antigenic properties. It is assumed that thermostable factors on a surface of enterocytes communicate with specific a glycoprotein-nym a receptor of the regulator controlling consumption by cells of Sa ++.

Among thermolabile proteinaceous factors the choleragen produced by a cholera vibrio is most known. Choleragen termolabilen and after 10 — 15 min. warming up at t ° 56 ° is inactivated. Synthesis of choleragen and its secretion on Wednesday of cultivation are determined by two genes localized in a chromosome, one of to-rykh codes formation of subunits In, and the second — the sequence of subunit And. At cholera of subunit In choleragen are fixed on receptors of the enterocytes containing a ganglioside of GMi in the structure and together with this receptor penetrate in cytosol of target cells where from choleragen the subunit is chipped off And, activating intracellular adenylatecyclase.

Ability to development of other thermolabile proteinaceous factors similar to choleragen at the molecular weight, structure and the nature of the striking action, is inherent in V. cholerae of a biotype (biopitch) of bottoms — 01, V. fluvialis V. mimicus, Ai-romonas to hydrophila, A. punctata u Plesiomonas shigelloides. Thermolabile proteinaceous factors, similar to choleragen, develop also E. coli, Salmonella typhimuri-um, S. enteritidis, S. weltevreden, S. wien, S. newport, S. london, Klebsiella pneumoniae, Y. enterocolitica,

C. jejuni. However the thermo labile proteinaceous factors developed by escherichias, salmonellas and other enterobakteriya concede to choleragen on specific toxic activity. As receptors for them on enterocytes serve both gangliozidsoderzhashchy structures, and the structures constructed without participation of the last. Synthesis of these thermolabile proteinaceous factors unlike choleragen is determined by the genes localized in plasmids.

AA., breaking ability of enterocytes to soak up nutrients from a gleam of a gut, hl are presented. obr. rather thermostable proteins (maintain warming up at t ° 60 ° within 45 min.) with the expressed cytotoxic action. Thermostable proteins of this group of enterotoxins develop various strains E. coli, Shigella dysenteriae, S. typhimurium, S. enteritidis,

S. kapemba, S. thompsoni, V. para-haemolyticus, V. cholerae of a biotype (biopitch) of non — 01, V. fluvialis, V. vulnificus, Aeromonas hydrophila,

A. sobria, S. jejuni. The majority of thermostable factors immunochemical are similar. The striking effect of thermostable proteins explain them with ability to be fixed on receptors of enterocytes, to get into cytosol and to induce there a stop of a proteosintez at a stage of transfer of amino acids with acceptor RNA for polysom. Enter into this group also E. with the expressed cytotoxicity, developed by cultures of bacteria of the sorts Clostridium and Bacillus. In particular, C1 isolates. perfringens of biotypes And, C and D produce the thermolabile enterotoxin with a molecular weight of 34 000 — 35 000 which is inactivated after 5 min. warming up at t ° 57 °. This E. it is capable to penetrate in cytosol of enterocytes and to dissociate there on subcomponents, one of to-rykh functions at the same time as inhibitor of a proteosintez. Cultures of Cl. difficile also develop thermolabile E. with the expressed cytotoxicity. The striking action of it E. on enterocytes connect with blockade of a proteosintez, with ability to activate guanylate cyclase, and also with ability to influence process of receipt of Sa ++ in enterocytes. Thermo labile E. with a molecular weight apprx. 50 000 and the expressed cytotoxicity concerning enterocytes form also bacteria of types of Bacillus cereus, V. of mycoides, V. of thuringiensis. The action striking them is connected not only with ability to block proteosintez, but also with the activating action on adenylatecyclase.

In addition to two basic groups E. one more kind of this sort of microbic toxins — Staphylococcus aureus enterotoxins is known. 6 serotypes are described (And, B, C, D, E, F) staphylococcal E., synthesis and secretion to-rykh are coded by the genes having both plasmid, and chromosomal localization. Despite the expressed immunochemical heterogeneity all staphylococcal E. treat thermostable squirrels (maintain warming up at t ° 100 — 121 ° within 1 — 14 min.) with a molecular weight of 28 500 — 35 300 and the expressed ability to induce diarrhea, the mechanism of development the cut remains not found out. However staphylococcal enterotoxins have no serological relationship with any another microbic E., do not influence on guanilattsiklazny and adenylate-tsiklaznuyu activity of enterocytes

and, apparently, have no cytotoxicity.

Bibliography: D and l and M. V. N and F and sh N. G. Proteinaceous toxins of microbes, M., 1980; Stanislavsky E. S. and Volynsk M. Ya. Enterotoxins of enterobakteriya, Zhurn. mikr., epid. and immun., No. 10, page 3, 1976; In u x s e r S. and. In about p-ventre P. F. Staphylococcal enterotoxins fail to disrupt membrane integrity or synthetic functions of Henle 407 intestinal cells. Infect, a. Immun., v. 31, p. 929, 1981; Giannella R. A. Escherichia coli heat-stable enterotoxin, biochemical and physiological effects on the intestine, Progr. Focd Nutr. Sci., v. 7, p. 157, 1983. See also bibliogr. to St. Toxins.

M. V. Dalin.

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