Isolation and purification of two human liver UDP-glucuronosyltransferases.
Two UDP-glucuronosyltransferases (EC 2.4.1.17) were purified from human liver microsomes. Human liver microsomes were solubilized with Emulgen 911 and the UDP-glucuronosyltransferases were separated and purified by chromatofocusing and UDP-hexanolamine Sepharose 4B affinity chromatography. One isoenzyme eluted with an apparent pl of 7.4, displayed a subunit molecular weight of 53,000 after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and catalyzed the glucuronidation of p-nitrophenol, 4-methylumbelliferone, alpha-naphthylamine, and estriol, but not that of 4-aminobiphenyl. A second isoenzyme eluted with an apparent pl of 6.2, displayed a subunit molecular weight of 54,000 after SDS-PAGE, and catalyzed the glucuronidation of p-nitrophenol, 4-methylumbelliferone, alpha-naphthylamine, and 4-aminobiphenyl, but not that of estriol. Neither of the purified human liver UDP-glucuronosyltransferases employed estrone, beta-estradiol, testosterone, androsterone, or 5 alpha-androstane-3 alpha,17 beta-diol as substrate. These enzymes displayed apparent Km values in the same order of magnitude for a given substrate. In general, high concentrations of phosphatidylcholine were required for reconstitution of maximal glucuronidation activity. This report documents the existence of multiple UDP-glucuronosyltransferases in human liver.
D005965:Glucuronates / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000302:isolation & purification* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology; D008970:Molecular Weight; D010713:Phosphatidylcholines / Q000502:physiology; D013379:Substrate Specificity
D005965:Glucuronates; D007527:Isoenzymes; D010713:Phosphatidylcholines; D014453:Glucuronosyltransferase