Nuclear membrane-bound UDPglucuronosyltransferase of rat liver.
Some properties of rat liver nuclear membrane-bound UDPglucuronosyltransferase were compared with those of the endoplasmic reticulum bound enzyme. The activity of nuclear membrane-bound UDPglucuronosyltransferase was stimulated only about 1.5-fold by Lubrol WX. Under the same conditions microsomal UDPglucuronosyltransferase was, as usual, highly activated (up to 10-fold), when 4-nitrophenol was the acceptor of glucuronic acid. Specific activities of the detergent-activated enzyme were similar in microsomal and nuclear membrane preparations, when the following aglycone substrates were used: 4-methylumbelliferone, 4-nitrophenol, 1-naphthol, phenolphthalein, and testosterone. Apparent Km values for UDP-glucuronic acid ranged between 0.15-0.25 mM for glucuronidation of 4-nitrophenol and 1-naphthol, by either Lubrol WX activated or non-activated, nuclear membrane-bound UDPglucuronosyltransferase. These values were comparable to those found for detergent activated microsomal enzyme. The results show a similarity in behavior of detergent-activated UDPglucuronosyltransferase regardless of subcellular membrane source and, therefore, suggest the association of the same glucuronosyltransferase with nuclear membrane and endoplasmic reticulum. A possible significance of the presence of high activity of this enzyme in nuclear membrane is discussed.
D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005965:Glucuronates / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D009685:Nuclear Envelope / Q000201:enzymology*; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats
D005965:Glucuronates; C017474:Lubrol WX; D011092:Polyethylene Glycols; D017830:Octoxynol; D014453:Glucuronosyltransferase