Phenol sulphotransferase and uridine diphosphate glucuronyltransferase from rat liver in vivo and in vitro. 2,6-Dichloro-4-nitrophenol as selective inhibitor of sulphation

Abstract

Microsomal UDP-glucuronyltransferase and cytosolic sulphotransferase share many substrates, such as phenols and hydroxamic acids. In a search for a selective inhibitor of sulphation, several phenolic compounds were tested. 2,6-Dichloro-4-nitrophenol is introduced as a selective inhibitor of sulphation in vivo, having no effect on UDP-glucuronyltransferase activity. As substrate for both conjugating enzymes the phenolic drug harmol (7-hydroxy-1-methyl-9H-pyrido[3,4-b]indole) was used. In the rat in vivo 2,6-dichloro-4-nitrophenol caused almost complete inhibition of harmol sulphation after a single intraperitoneal injection (26mumol/kg) for 48h; the percentage of harmol sulphated decreased from 75% in controls to 5% in the treated rats. The percentage of harmol glucuronidated increased from 25 to 95%. Pentachlorophenol was equally effective but also highly toxic. Salicylamide had only a very-short-lasting inhibitory effect on sulphation. In vitro, 2,6-dichloro-4-nitrophenol inhibited sulphation of harmol by a rat liver postmitochondrial supernatant completely at 1mum, whereas even at 100mum it had no effect on glucuronidation of harmol. It is concluded that 2,6-dichloro-4-nitrophenol is a selective inhibitor of sulphation and, further, that its long duration of action makes it suitable for studies on the regulatory role of sulphation in some biological processes.

Localization and Functional Analysis of the Substrate Specificity/Catalytic Domains of Human M-form and P-form Phenol Sulfotransferases

“…The other two phenol sulfotransferases, designated the P-form phenol sulfotransferases, preferentially catalyze the sulfation of simple phenolic compounds such as p-nitrophenol (16 -18). In addition to their distinct substrate specificity, earlier studies have demonstrated M-form PST to be markedly more thermolabile and 3 orders of magnitude less sensitive to inhibition by 2,6-dichloro-4-nitrophenol (DCNP), a sulfation inhibitor (19). Our recent study also showed that, in contrast to P-form PSTs, M-form PST displayed stereoselective and manganese-dependent Dopa/tyrosine sulfotransferase activities (20).…”

Tyrosine sulphation is not required for microvillar expression of intestinal aminopeptidase N

“…If tyrosine sulphation is of importance for microvillardirected transport (for instance as a sorting signal), one should expect that interference of this type of processing would obscure the intracellular transport of newly synthesized microvillar enzymes, either by retarding their apical expression or possibly by causing an intracellular mis-sorting, leading to accumulation of microvillar enzymes in other organelles. DCNP has been described to inhibit selectively the phenol sulphotransferase from rat liver in vivo as well as in vitro (Mulder & Scholtens, 1977). In the latter case 0.1 U/M caused about 50 % inhibition and complete inhibition was achieved at 1 gM.…”

“…2,6-Dichloro-4-nitrophenol (DCNP) has been reported to inhibit phenol sulphotransferases both in vivo and in vitro (Mulder & Scholtens, 1977). In the present paper, DCNP was used to affect tyrosine sulphation in organ-cultured mucosal explants as a means to investigate the importance of this type of processing in the biosynthesis of the microvillar enzymes of the enterocyte.…”

Expression and Functional Characterization of a Rat Sulfotransferase (ST1A1) cDNA for Sulfations of Phenolic Substrates in COS-1 Cells

“…Addition of pen tachlorophenol (PCP) at 1 pM and 10 pM inhibited p nitrophenol sulfating activity by 50% and 79% in the livers of male rats and by 39% and 68% in cDNA-ex pressed cells, respectively. These results on substrate specificity and susceptibility to PCP (12) indicate that PST-1 encodes a member of the arylsulfotransferase fami ly, STIAI. The specific content of STIAI in COS-1 cytosols was quantitated and determined to be half that observed in the livers of male and female rats in Western blots.…”