Sulfite is generated from PAPS by activated neutrophils.

We previously reported that neutrophils produce sulfite in response to stimulation with lipopolysaccharide, and sulfite production is dependent on inorganic sulfate contained in culture media. Microorganisms such as yeast assimilate sulfate, during which process sulfite is generated by reduction of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), an activated sulfate donor. However, little is known about how sulfite is produced in mammalian cells. In the current study, we demonstrated that chlorate, a specific inhibitor for PAPS synthesis, significantly suppressed production of sulfite by activated neutrophils obtained from rat peritoneal cavity that had been injected with glycogen to induce inflammation. Addition of excess amounts of PAPS could partially overcome the inhibitory effect of chlorate. Moreover, sulfite production from PAPS was clearly demonstrated in the cytosolic fraction of activated neutrophils. These findings strongly suggest that sulfite is generated, at least in part, from PAPS by activated neutrophils.

Characterization of 3'-phosphoadenosine 5'-phospho[35S]sulfate transport carrier from rat brain microsomes.

3'-Phosphoadenosine 5'-phospho[35S]sulfate [( 35S]PAPS) specific binding properties of rat brain tissue were studied. [35S]PAPS specific binding was optimal at pH 5.8 in either Tris-maleate or potassium phosphate buffers. Association was maximal at low temperature, reaching equilibrium in 20 min. Dissociation was rapid, with a dissociation time of 80 s. Scatchard analysis of [35S]PAPS specific binding was consistent with a single site having a KD of 0.46 +/- 0.06 microM and a Bmax of 20.8 +/- 2.0 pmol/mg of protein. Low concentrations of Triton X-100 (0.025%) were effective in increasing the number of binding sites to a Bmax of 44.5 +/- 4.6 pmol/mg of protein without affecting the affinity. [35S]PAPS specific binding was enriched in crude synaptic membranes (P2) and microsomes (P3). Regional distribution of [35S]PAPS specific binding was quite homogeneous in all brain structures studied. The pharmacological profile of [35S]PAPS specific binding in rat brain microsomes was consistent with a membrane protein having a high selectivity for the 3'-O-phosphoryl group substitution on the ribose moiety. Thus, 3'-phosphoadenosine 5'-phosphate was more potent than 2'-phosphoadenosine 5'-phosphate in competing for [35S]PAPS specific binding. Adenosine 5'-phosphosulfate was a good inhibitor of [35S]PAPS specific binding. ATP and ADP were also good displacers. Dipyridamole, a highly selective marker for adenosine uptake sites, was ineffective. 4,4-Diisothiocyanostilbene-2,2-disulfonic acid, the chloride transporter inhibitor, showed an IC50 of 36 +/- 5.1 microM for inhibition of [35S]PAPS specific binding. 2,6-Dichloro-4-nitrophenol had a low selectivity in competing for the [35S]PAPS binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Human platelet phenol sulphotransferase: assay procedure, substrate and tissue correlations.

Procedures for the precise assay of human platelet phenol sulphotransferase activity were determined. The coefficient of variation of the assay was 5.8% when the enzyme activity was expressed per 10(8) platelets, and was 9.4% when it was expressed per mg soluble platelet protein. Mean platelet phenol sulphotransferase (PST) activity in samples from 102 randomly selected adults was 1.2 +/- 0.4 units/10(8) platelets (mean +/- S.D.), with a range from 0.2 to 2.9. The mean activity for umbilical cord blood platelet PST was 0.93 +/- 0.3 units/10(8) platelets (mean +/- S.D., n = 27). The substrate used routinely for the assay was 3-methoxy-4-hydroxyphenylglycol (MHPG). There was a significant correlation between the formation of MHPG sulfate by individual platelet preparations and the formation of sulfated product with each of the following substrates: tyramine (r = 0.92, n = 21); dopamine (r = 0.82, n = 16); 5-hydroxytryptamine (r = 0.94, n = 20); acetaminophen (r = 0.77, n = 17); and alphamethyldopa (r = 0.77, n = 17) (p less than 0.001 for each). Platelet PST activity correlated significantly with human renal cortex PST activity (r = 0.54, n = 20, p less than 0.02). The correlation coefficient between platelet PST activity and jejunal mucosal enzyme activity in eight patients was 0.67. These results raise the possibility that human platelet PST activity measured with MHPG as substrate might reflect the enzyme activity in other tissues and the degree of sulfate conjugation of a variety of substrates.