Molecular cloning, expression, localisation and functional characterisation of a rabbit SULT1C2 sulfotransferase

The importance of sulfotransferases in xenobiotic metabolism is gaining rec ognition. The gastrointestinal (CI) tract is a major portal of entry for ma ny xenobiotics, yet little is known about the contribution of sulfotransfer ases to detoxication or bioactivation metabolism in these tissues. To this end, isolation and characterisation of sulfotransferases expressed in the s tomach of rabbits was undertaken. A unique sulfotransferase cDNA (GenBank A ccession No. AF026304) was isolated from a rabbit stomach cDNA library. Thi s cDNA was 1439 base pairs (bp) long and has an open reading frame of 888 b p. On expression of the cDNA in both COS cells and E. coil, a protein molec ular weight of 34 kDa was detected on SDS-PAGE. Immunoblotting using an ant ibody raised in goats against the bacterially expressed protein detected ex pression of the protein in GI tract tissues. The 34 kDa immunoreactive band was detected in rabbit GI tract tissues (stomach, duodenum,jejunum, ileum, colon, caecum and rectum), liver and kidneys, but not in the lungs (n = 3) . The human ortholog (GenBank Accession No AF026303) of the rabbit enzyme w as cloned from a human stomach cDNA library. These two enzymes share 84% am ino acid sequence identity and have been termed 1C2 sulfotransferases. When functional and kinetic characterisation of the recombinant rabbit and huma n proteins was carried out using 16 known ST substrates, detectable sulfona tion activity was observed only with p-nitrophenol (with K-m values of 2.2 mM and 13.3 mM, respectively). In conclusion, we have identified a rabbit G I tract sulfotransferase belonging to a newly defined sulfotransferase subf amily. (C) 1999 Elsevier Science Ltd. All rights reserved.