GLUCURONIDASE

From Big Medical Encyclopedia

GLUCURONIDASE (KF 3. 2. 1. 31; beta D - a glucuronide-glyukuronogidrolaza; beta glucuronidase) — enzyme of a class of hydrolases and group of hydrolases of glycosides, catalyzes hydrolytic decomposition beta D - glucuronides with education D-glucuronic to - you, and also reactions of a transglycosylation; genetic insufficiency of this enzyme is the reason of a hereditary disease — a mukopolisakharidoza of the VII type.

Drugs G. are used for measurement of maintenance of 17 oxycorticosteroids and their tetrahydroderivatives in urine and blood serum during the definition of function of bark of adrenal glands.

It is found in microorganisms, plants and animals. At mammal G. contains in the majority of fabrics and biol, liquids. The richest source of G. is preputial gland.

The first data on G. are received in 1934 when from kidneys of a bull emitted fermental drug, with the help to-rogo hydrolysis of beta glucuronides was carried out.

In bodies and tissues of mammals and the person G. it is localized in lizosomalny fraction and fraction of cytoplasmic membranes. Subcellular forms G. have a number of close properties, but differ on electrophoretic mobility and behavior on ion exchangers.

High cleaning, and in some cases homogeneous drugs G, are received from a liver of a calf, a rat and a rabbit. The optimum of pH of action of G. from different sources is ranging from 4,5 to 5,2. The isoelectric point is defined at pH 5,8 — 6,15.

It is inhibited by ions of heavy metals, steam-hlormerkuribenzoatom, D - a glyukaro-1,4-lactone.

Pier. the weight (weight) of G. makes 260 000 — 300 000 of different sources. Enzyme represents tetramer about a pier. weighing 68 000 — 75 000 subunits. Is glycoprotein (see). Drugs of enzyme from various sources differ among themselves both by quantity, and on structure of a carbohydrate (glyconew) part, edges is presented by mannose, a glycosamine, fukozy, a galactose and glucose.

Methods of definition of activity of G. are based on release of phenolphthalein, nitro - or aminophenol, and also the enzyme possessing fluorescence of 4-methyl-umbelliferone from the corresponding synthetic beta glucuronides at action on them.

G.'s ability to release steroids from steroidglyukuronovy to - t is used in clinic for determination of the general content of steroid hormones in urine and blood serum. Along with other glucosidases participates in disintegration of the mucopolysaccharides which are obligatory components of connecting fabric. G.'s absence as a result of genetic defect leads to a serious hereditary illness — a mukopolisakharidoz of the VII type (see. Mukopolisakharidoza ). At this disease in human organs a large amount of various glyukuronidsoderzhashchy mucopolysaccharides — hondroitinsulfat, hyaluronic to - you, a dermatansulfat, heparin and a geparansulfat collects and allocated with urine. G.'s absence and simultaneous accumulation in them of significant amounts of mucopolysaccharide can serve as the additional test at diagnosis of a mukopolisakharidoz of the VII type in culture of fibroblasts. Addition to culture of fibroblasts of beta glucuronidase leads to normalization of disintegration of mucopolysaccharides.

See also Glucuronides .


Bibliography Heftman E. Biochemistry of steroids, the lane with English, M., 1972, bibliogr.; L e v v at G. A. a. Marsh of Page A. 0-Glucuronidase, in book: The enzymes, ed. by P. D. Boyer a. o., v. 4, p. 397, N. Y. — L.f I960; T o m i n o S. a, o. Purification and chemical properties of mouse liver lysosomal (L form) 0-glucuronidase, J. Biol. Chem., v. 250, p. 8503, 1975, bibliogr.

H. A. Ushakova.

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