Purification and characterization of two amine N-sulfotransferases, AST-RB1 (ST3A1) and AST-RB2 (ST2A8), from liver cytosols of male rabbits

Two sulfotransferases (STs), designated as AST-RB1 (ST3A1) and AST-RBS (ST2 A8), with high a amine N-sulfonating activity, were purified from male rabb it liver cytosols, AST-RB1 and AST-RBS were purified to homogeneity by the anion-exchange, affinity, and hydroxyapatite chromatography. The N-terminus of both enzymes were blocked. The subunit molecular mass of both enzymes w as estimated to be 34 kDa on SDS-PAGE, AST-RB1 efficiently catalyzed N-sulf onation of alicyclic, alkyl, and arylamines such as 4-phenyl-1,2,3,6-tetrah ydropyridine, 1-[(5-chloro-2-oxo-3 (2H)-benzothiazolyl)acetyl]-piperazine, desipramine, and aniline, whereas its catalytic activities toward a-naphtho l and dehydroepiandrosterone (DHEA) were very low. On the other hand, AST-R B2 efficiently catalyzed sulfonation of desipramine and DHEA, but had no ac tivity toward a-naphthol, Amino acid sequences of peptide fragments derived from the purified AST-RB1 showed no significant homology with previously r eported STs, but those from the purified AST-RB2 shared a high similarity w ith those of the ST2 family. Both enzymes were expressed specifically in th e liver, The present results strongly suggest that the purified AST-RB1 is a novel enzyme in terms of structure and catalytic properties showing high selectivity for amine substrates, and AST-RB2 is a quite unique from among ST2A enzymes of other species in its substrate specificity. (C) 1999 Academ ic Press.