Biomaterial Database

Formation of bile acid glucosides by a sugar nucleotide-independent glucosyltransferase isolated from human liver microsomes. 1984

H Matern, and S Matern, and W Gerok

A heat-labile protein has been detected in microsomes from human liver which catalyzes the formation of glucosides of the bile acids chenodeoxycholic, deoxycholic, and ursodeoxycholic acids. This glucosyltransferase activity has been purified about 900-fold from human liver microsomes, resulting in homogeneity as determined by sodium dodecyl sulfate gel electrophoresis. The subunit molecular weight was calculated to be about 56,000. The enzyme was separated from bile acid UDP-glucuronosyltransferase [UDP-glucuronate beta-D-glucuronosyltransferase (acceptor-unspecific), EC 2.4.1.17] during purification and does not catalyze the formation of bile acid glucuronides. The purified glucosyltransferase utilizes lipophilic alkyl beta-D-glucopyranosides as artificial donor substrates and dolichyl phosphoglucose as natural donor for the transfer of glucose to bile acids and does not exhibit bile acid conjugating activity in the presence of sugar nucleotides such as UDP-glucose. The apparent Km values estimated for various alkyl beta-D-glucopyranosides decreased with increasing alkyl chain length from 680 X 10(-6) M for hexyl beta-D-glucopyranoside to 20 X 10(-6) M as estimated for decyl and dodecyl beta-D-glucopyranoside. The results suggest that a glucoside-conjugation pathway of bile acids exists in humans. This conjugation is catalyzed by a sugar nucleotide-independent glucosyltransferase and is therefore distinct from the known mechanisms of glycoside conjugation.

UI	MeSH Term	Description	Entries
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D002384	Catalysis	The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.	Catalyses
D002635	Chenodeoxycholic Acid	A bile acid, usually conjugated with either glycine or taurine. It acts as a detergent to solubilize fats for intestinal absorption and is reabsorbed by the small intestine. It is used as cholagogue, a choleretic laxative, and to prevent or dissolve gallstones.	Chenic Acid,Chenodeoxycholate,Chenodiol,Gallodesoxycholic Acid,Chenique Acid,Chenix,Chenofalk,Chenophalk,Henohol,Quenobilan,Quenocol,Sodium Chenodeoxycholate,Acid, Chenic,Acid, Chenique,Acid, Chenodeoxycholic,Acid, Gallodesoxycholic,Chenodeoxycholate, Sodium
D005964	Glucosyltransferases	Enzymes that catalyze the transfer of glucose from a nucleoside diphosphate glucose to an acceptor molecule which is frequently another carbohydrate. EC 2.4.1.-.	Glucosyltransferase
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D001647	Bile Acids and Salts	Steroid acids and salts. The primary bile acids are derived from cholesterol in the liver and usually conjugated with glycine or taurine. The secondary bile acids are further modified by bacteria in the intestine. They play an important role in the digestion and absorption of fat. They have also been used pharmacologically, especially in the treatment of gallstones.	Bile Acid,Bile Salt,Bile Salts,Bile Acids,Acid, Bile,Acids, Bile,Salt, Bile,Salts, Bile
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities