Purification and properties of a rat liver phenobarbital-inducible 4- hydroxybiphenyl UDP-glucuronosyltransferase

P Styczynski, M Green, J Puig, B Coffman and T Tephly

Department of Pharmacology, University of Iowa, Iowa City 52242.

A phenobarbital-inducible rat hepatic microsomal UDP- glucuronosyltransferase (UDPGT) that catalyzes the glucuronidation of 4- hydroxybiphenyl (4-HBP) has been purified to homogeneity. This UDPGT has an apparent subunit molecular weight of 52,500, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 4-HBP UDPGT was shown to catalyze the glucuronidation of 4-HBP, 4- methylumbelliferone, and p-nitrophenol but did not react with testosterone, androsterone, morphine, chloramphenicol, 4- hydroxycoumarin, or 7-methoxycoumarin. The apparent Km of 4-HBP UDPGT for 4-HBP was determined to be 0.26 mM and for UDPGA was 1.0 mM. Upon treatment with endoglycosidase H, the 4-HBP UDPGT underwent about a 2000-dalton decrease in subunit molecular weight, suggesting that this protein is N-glycosylated. Additionally, this protein demonstrated immunoreactivity with antibodies raised in rabbit against rat 17 beta- hydroxysteroid and 3 alpha-hydroxysteroid UDPGTs. This work describes the purification and characterization of a 4-HBP UDPGT from rat liver microsomes and, furthermore, provides evidence that suggests that this UDPGT is different from another UDPGT previously shown to react with 4- HBP and chloramphenicol.

Volume 40, Issue 1, pp. 80-84, 07/01/1991
Copyright © 1991 by American Society for Pharmacology and Experimental Therapeutics

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