Sulfation of aromatic hydroxamic acids and hydroxylamines by multiple forms of human liver sulfotransferases

Abstract

Sulfation activity towards various heterocyclilc and homocyclic aromatic hydroxamic acids and hydroxylainines was determined in adult human liver cytosol and with partially purified human liver sulfofransferases (STs). In adult human liver cytosols comparable ST activities towards N-hydroxy-2-acetyl-amino-5-phenylpyridine (N-OH-2AAPP), N-hydroxy-4-acetyl-aminobiphenyl (N-OH-4AABP) and N-hydroxy-4′fluoro-4-acetylaminobiphenyl (N-OH-4FAABP) were found, while the sulfation rates towards N-hydroxy-2-acetylaminofluorene (N-OH-2AA N-hydroxy-2-acetylaminonaphthalene (N-OH 2AAN), N-hydroxy-2-acetylamlnophenanthrene (N-OH-2AAP) and N-hydroxy-4-acetylaminostilbene (N-OH-4AAS) were two- to five-fold lower. In adult liver cytosol ST activity was found towards all hydroxylamines tested. No significant differences were found for the various hydroxylainines. In general, the ST activities towards the various hydroxamic acids and hydroxylamines were comparable to phenol ST activity using adult liver cytosols. Partial purification of adult human liver STs was achieved by DEAE-Sepharose chromatography followed by anion exchange FPLC. Two separated protein peaks showing both N-OH-2AAPP and N-OH-2APP ST activities were observed and were designated human hydroxylamine/hydroxamic acid sulfotransferase (hHST) 1 and 2. Iimmunoblot analysis using an anti-rat estrogen ST antibody demonstrated cross reactivity with both hHSTs at a subunit mol. wt of 32 kDa corresponding to the phenol-sulfating form of phenol ST (P-PS ST activity towards dopamine was low with both hHSTs, but hHST1 also contained significant capacity to sulfate dehydroepiandrosterone. The highest ST activity towards N-OH-2AAPP and N-OH-2APP was measured at pH 5.5 with both hHSTs. The K_m values of the two hHSTs for sulfation of N-OH-2AAPP