A novel type of arylsulfotransferase

Abstract

Arylsulfotransferase catalyzes the transfer of a sulfate group from 3′-phosphoadenosine-5′-phosphosulfate (PAPS) to a phenolic acceptor substrate. We discovered a novel type of sulfotransferase from an anaerobic bacterium of human intestine, Eubacterium A-44. In the bacterial enzyme PAPS did not serve as a donor and all alcohols did not as acceptors. The new arylsulfotransferase was purified 185-fold from a crude extract of sonicated bacteria to homogeneity. The enzyme (MW 315 kd) was composed of four identical subunits (MW 80 kd) whose N-terminal amino acid was arginine, and its optimal pH and pI were 8–9 and 3.9, respectively. The enzyme catalyzed stoichiometric transfer of a sulfate group from a phenol sulfate ester to other phenols, with strict specificity. With tyramine as an acceptor, p-acetylphenyl sulfate was the best donor, followed by 4-methylumbelliferyl sulfate and p-nitrophenyl sulfate. With p-nitrophenyl sulfate as a donor, naphthol was the best acceptor, followed by estradiol, phenol, tyrosine methylester, tyramine, and epinephrine in decreasing order. Only the 4-position of catecholamines was specifically sulfated. Naturally occurring phenolic compounds, such as flavone, chalcone, and xanthone, were sulfated as well. Tyrosine-containing peptides were enzymatically sulfated: enkephalin, LH-RH, vasopressin, angiotensins, proctorin, CCK-8, and phyllocaerulein were sulfated with high yields. The novel sulfotransferase is expected to be applicable to enzymatic O-sulfation of tyrosine-containing hormones. The 35S-labeled sulfate group from (35S)p-nitrophenyl sulfate was incorporated into a tyrosyl residue at the active site of the enzyme (2 mole 35S/mole of enzyme). The enzyme was inactivated by diethylpyrocarbamate and TLCK, chemical modifying agents for a histidyl residue. The reaction mechanism of arylsulfotransferase was proposed as follows: a donor substrate combines a histidyl residue with concomitant release of a phenolic compound. The sulfate group of the histidyl residue transfers to a tyrosyl residue, and then to an acceptor with the binding of another donor substrate to the histidyl residue.