PURIFICATION AND CHARACTERIZATION OF A CANINE LIVER PHENOL SULFOTRANSFERASE

Species differences in the metabolism of xenobiotics can present signi ficant problems for safety and efficacy assessment during the developm ent of new pharmaceutical agents. Identification of animal models for human metabolism and/or toxicology of any particular compound would si gnificantly reduce the extent and cost of animal testing of novel cand idate pharmaceuticals. Sulfation is an important pathway for metabolis m of xenobiotics and potent endogenous compounds and is catalyzed by m embers of the sulfotransferase enzyme family. We have purified a pheno l sulfotransferase from male dog liver cytosol which sulfates simple p henolic compounds such as 1-naphthol and 4-nitrophenol. On SDS-polyacr ylamide gel electrophoresis, the protein had a subunit molecular weigh t of approximately 32,000 Da and was 34,200 Da by electrospray mass sp ectrometry. Immunoblot analysis with an antipeptide antibody specific for the human phenol-sulfating form of phenol sulfotransferase (P-PST, 1A1) suggested the protein was highly homologous to the human P-PST e nzyme. This was supported by amino acid sequence analysis of four pept ides derived from the purified enzyme and by comparison with sequences of other phenol sulfotransferases, which showed the highest identity with human and monkey orthologs. Our data illustrate the high degree o f conservation of phenol sulfotransferases across mammalian species an d suggest that this dog liver enzyme is more closely related to the hu man P-PST than equivalent proteins in rats and mice.