Purification and characterization of a canine liver phenol sulfotransferase

Species differences in the metabolism of xenobiotics can present significant problems for safety and efficacy assessment during the development of new pharmaceutical agents. Identification of animal models for human metabolism and/or toxicology of any particular compound would significantly reduce the extent and cost of animal testing of novel candidate pharmaceuticals. Sulfation is an important pathway for metabolism of xenobiotics and potent endogenous compounds and is catalyzed by members of the sulfotransferase enzyme family. We have purified a phenol sulfotransferase from male dog liver cytosol which sulfates simple phenolic compounds such as 1-naphthol and 4-nitrophenol. On SDS-polyacrylamide gel electrophoresis, the protein had a subunit molecular weight of approximately 32,000 Da and was 34,200 Da by electrospray mass spectrometry. Immunoblot analysis with an anti-peptide 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 enzyme. This was supported by amino acid sequence analysis of four peptides 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 of conservation of phenol sulfotransferases across mammalian species and suggest that this dog liver enzyme is more closely related to the human P-PST than equivalent proteins in rats and mice.