Examination of the substrate specificity of cloned rat kidney phenol UDP-glucuronyltransferase expressed in COS-7 cells.

A cDNA encoding a rat kidney UDP-glucuronyltransferase (UDPGT) was subcloned into the vector pKCRH2. Expression driven by the SV40 promoter produced enzymatically active UDPGT in COS-7 cells cultured in vitro. The appearance of enzyme activity was associated with an immunodetectable glycosylated UDPGT protein (Mr 53 kDa) in the cells. The expressed enzyme rapidly catalyzed the glucuronidation of 1-naphthol, 4-methylumbelliferone, and 4-nitrophenol. Studies using more than 20 compounds showed that the cloned UDPGT exhibited a restricted specificity towards planar phenols. A crude description of the molecular conformation of 4-alkylphenols accepted within the active site of the protein was obtained. The glucuronidation of morphine, thymol, menthol, testosterone, androsterone, or estrone was not catalyzed by this enzyme.