Phenol Sulfotransferase Activity Research Articles

Ontogeny of Pediatric Pharmacogenetics: Celebrating the Past and Vision for the Future.

Ontogeny of Pediatric Pharmacogenetics: Celebrating the Past and Vision for the Future.

Decreased phenol sulfotransferase activities associated with hyperserotonemia in autism spectrum disorders

Hyperserotonemia is the most replicated biochemical abnormality associated with autism spectrum disorders (ASD). However, previous studies of serotonin synthesis, catabolism, and transport have not elucidated the mechanisms underlying this hyperserotonemia. Here we investigated serotonin sulfation by phenol sulfotransferases (PST) in blood samples from 97 individuals with ASD and their first-degree relatives (138 parents and 56 siblings), compared with 106 controls. We report a deficient activity of both PST isoforms (M and P) in platelets from individuals with ASD (35% and 78% of patients, respectively), confirmed in autoptic tissues (9 pineal gland samples from individuals with ASD—an important source of serotonin). Platelet PST-M deficiency was strongly associated with hyperserotonemia in individuals with ASD. We then explore genetic or pharmacologic modulation of PST activities in mice: variations of PST activities were associated with marked variations of blood serotonin, demonstrating the influence of the sulfation pathway on serotonemia. We also conducted in 1645 individuals an extensive study of SULT1A genes, encoding PST and mapping at highly polymorphic 16p11.2 locus, which did not reveal an association between copy number or single nucleotide variations and PST activity, blood serotonin or the risk of ASD. In contrast, our broader assessment of sulfation metabolism in ASD showed impairments of other sulfation-related markers, including inorganic sulfate, heparan-sulfate, and heparin sulfate-sulfotransferase. Our study proposes for the first time a compelling mechanism for hyperserotonemia, in a context of global impairment of sulfation metabolism in ASD.

A nano switch mechanism for the redox-responsive sulfotransferase

Cellular redox signaling is important in diverse physiological and pathological processes. The activity of rat phenol sulfotransferase (rSULT1A1), which is important for the metabolism of hormone and drug, is subjected to redox regulation. Two cysteines, Cys232 and Cys66, nanometer away from each other and from the enzyme active site were proposed to form disulfide bond to regulate the activity of rSULT1A1. A nano switch, composed of a flexible loop from amino acid residues 59–70, explained how this long distance interaction between two cysteines can be achieved. The enzyme properties were investigated through site-directed muatagnesis, circular dichroism, enzyme kinetics and homologous modeling of the rSULT1A1 structures. We proposed that the formation of disulfide bond between Cys232 and Cys66 induced conformational changes of sulfotransferase, then in turn affected its nucleotide binding and enzyme activity. This discovery was extended to understand the possible redox regulation of other sulfotransferases from different organisms. The redox switch can be created in other redox-insensitive sulfotransferases, such as human phenol sulfotransferase (hSULT1A1) and human alcohol sulfotransferase (hSULT2A1), to produce mutant enzymes with redox regulation capacity. This study strongly suggested that redox regulation of drug and hormone metabolism can be significantly varied even though the sequence and structure of SULT1A1 of human and rat have a high degree of homology.

Pomegranate Juice Inhibits Sulfoconjugation in Caco-2 Human Colon Carcinoma Cells

Several fruit juices have been reported to cause food-drug interactions, mainly affecting cytochrome P450 activity; however, little is known about the effects of fruit juices on conjugation reactions. Among several fruit juices tested (apple, peach, orange, pineapple, grapefruit, and pomegranate), pomegranate juice potently inhibited the sulfoconjugation of 1-naphthol in Caco-2 cells. This inhibition was both dose- and culture time-dependent, with a 50% inhibitory concentration (IC(50)) value calculated at 2.7% (vol/vol). In contrast, no obvious inhibition of glucuronidation of 1-naphthol in Caco-2 cells was observed by any of the juices examined. Punicalagin, the most abundant antioxidant polyphenol in pomegranate juice, was also found to strongly inhibit sulfoconjugation in Caco-2 cells with an IC(50) of 45 microM, which is consistent with that of pomegranate juice. These data suggest that punicalagin is mainly responsible for the inhibition of sulfoconjugation by pomegranate juice. We additionally demonstrated that pomegranate juice and punicalagin both inhibit phenol sulfotransferase activity in Caco-2 cells in vitro, at concentrations that are almost equivalent to those used in the Caco-2 cells. Pomegranate juice, however, shows no effects on the expression of the sulfotransferase SULT1A family of genes (SULT1A1 and SULT1A3) in Caco-2 cells. These results indicate that the inhibition of sulfotransferase activity by punicalagin in Caco-2 cells is responsible for the reductions seen in 1-naphthyl sulfate accumulation. Our data also suggest that constituents of pomegranate juice, most probably punicalagin, impair the enteric functions of sulfoconjugation and that this might have effects upon the bioavailability of drugs and other compounds present in food and in the environment. These effects might be related to the anticarcinogenic properties of pomegranate juice.

Sulfotransferase activities towards xenobiotics and estradiol in two marine fish species ( Mullus barbatus and Lepidorhombus boscii): Characterization and inhibition by endocrine disrupters

We have characterized hepatic phenol sulfotransferase (SULT) activities in two benthic fish species, Mullus barbatus and Lepidorhombus boscii, using p-nitrophenol, dopamine, 17β-estradiol, 4-nonylphenol, and 1-naphthol as substrates. High affinity sulfation of 17β-estradiol was observed in both species ( K m = 28–75 nM), suggesting the presence of a specific estrogen sulfotransferase that catalyzes the formation of estradiol-3 sulfate. Among the tested compounds, 1-naphthol was the most effective substrate for sulfation, with V max/ K m ratios several hundred-fold higher than the other substrates examined. Both species sulfated the tested compounds, but only M. barbatus was able to sulfate dopamine. We also tested the inhibitory effects of common marine pollutants with estrogenic (4-nonylphenol) and androgenic (tributyltin, triphenyltin) properties on p-nitrophenol and 17β-estradiol SULT activities. 4-Nonylphenol and triphenyltin inhibited sulfation of both substrates at micromolar concentrations in both species. However, tributyltin was only effective against SULTs from L. boscii, again at micromolar concentrations. The data indicate that M. barbatus and L. boscii are able to sulfate a range of xenobiotics and endogenous compounds, and inhibition of these activities by environmental pollutants may contribute to the known toxic effects of these compounds.

Turmeric and Curcumin Modulate the Conjugation of 1-Naphthol in Caco-2 Cells

Turmeric, the powdered dry rhizome of the Curcuma longa plant, and curcumin, the major anti-oxidant constituent of turmeric, have been shown to possess chemopreventive activity. To elucidate the possible interaction of turmeric and curcumin with conjugation reactions, which in many cases are involved in the activation of procarcinogens, we measured their effects in the conjugation of 1-naphthol in Caco-2 cells, a human colon carcinoma cell line, within a 24 h period. Turmeric exhibits inhibitory activity toward both sulfo- and glucuronosyl conjugations of 1-naphthol at approximately the same levels (IC(50)=0.24 and 0.29 mg/ml, respectively). Curcumin inhibits sulfo-conjugation at lower concentrations (IC(50)=9.7 microg/ml), but only showed weak inhibition toward glucuronosyl conjugation of 1-naphthol in Caco-2 cells. In addition, turmeric was found to strongly inhibit in vitro phenol sulfotransferase (SULT) activity and demonstrate moderate inhibitory properties against UDP-glucuronosyl transferase (UGT) activity in Caco-2 cells (IC(50)=0.17 mg/ml and 0.62 mg/ml, respectively). Curcumin also strongly inhibits in vitro phenol sulfotransferase activity with an IC(50) of 2.4 microg/ml. Moreover, and in contrast to the moderate inhibition of UGT activity by turmeric and curcumin, both induce the expression of the UGT1A1 and UGT1A6 genes, revealed by real-time PCR analysis. These findings are indicative of a possible interaction of both turmeric and curcumin with conjugation reactions in the human intestinal tract and colon. This in turn may affect the bioavailability of therapeutic drugs and toxicity levels of environmental chemicals, particularly procarcinogens.

Induction of Phenolsulfotransferase Expression by Phenolic Acids in Human Hepatoma HepG2Cells

Phenolic acids are antioxidant phenolic compounds, widespread in plant foods, which contribute significant biological and pharmacological properties; some have demonstrated a remarkable ability to alter sulfate conjugation. However, the modulation mechanisms of antioxidant phenolic acids on phenolsulfotransferase activity have not yet been described. In the present study, the human hepatoma cell line, HepG2, was used as a model to investigate the effect of antioxidant phenolic acids on enzymatic activity and expression of one of the major phase II sulfate conjugation enzymes, P-form phenolsulfotransferase (PST-P). The results showed that gallic acid, gentisic acid, p-hydroxybenzoic acid, and p-coumaric acid increased PST-P activity, in a dose-dependent manner. A maximum of 4- and 5-fold induction of PST-P activity was observed for both gallic acid and gentisic acid; however, they showed an adverse effect on cell growth at higher concentrations. A 2- or 2.5-fold increase of PST-P activity was found with either p-coumaric or p-hydroxybenzoic acid treatment, whereas no significant effect was found for ferulic acid treatment. PST-P induction, by gallic acid, was further confirmed, using reverse transcription PCR and Western blotting techniques to measure mRNA expression and protein translation. A significant correlation (r = 0.74, p < 0.01) between the expressions of PST-P mRNA and the corresponding PST-P activity was observed. Thus, gallic acid increased PST-P protein expression in HepG2 cells, in a dose- and time-dependent manner. The results demonstrated that certain antioxidant phenolic acids could induce PST-P activity in HepG2 cells, by promoting PST-P mRNA and protein expression, suggesting a novel mechanism by which phenolic acids may be implicated in phase II sulfate conjugation.

A Mixture‐of‐Genotypes Model for the Distribution of Thermostable Phenol Sulfotransferase Activity

AbstractA statistical method for parametric density estimation based upon a mixture‐of‐genotypes model is developed for the thermostable phenol sulfotransferase (SULT1A1) activity which has a putative role in modifying risk for colon and prostate cancer/polyps. The EM algorithm for the general mixture model is modified to accommodate the genetic constraints and is used to estimate genotype frequencies from the distribution of the SULT1A1 phenotype. A parametric bootstrap likelihood ratio test is considered as a testing method for the number of mixing components. The size and power of the test is then investigated and compared with the conventional chi‐squared test. The relative risk associated with genotypes defined by this model is also investigated through the generalized linear model. This analysis revealed that a genotype with the highest mean value of SULT1A1 activity has greater impact on cancer risk than others. This result suggests that the phenotype with a higher SULT1A1 activity might be important in studying the association between the cancer risk and SULT1A1 activity. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Characterization of the rates of testosterone metabolism to various products and of glutathione transferase and sulfotransferase activities in rat intestine and comparison to the corresponding hepatic and renal drug-metabolizing enzymes

Metabolism of testosterone to various products (catalyzed by several different CYP isozymes) and the activities of phenol sulfotransferase (pST) and glutathione transferase (GST) in S9 fractions prepared from the mucosa of the duodenum, jejunum, ileum, caecum and upper and lower colon of male Sprague–Dawley rats were determined and compared to the corresponding hepatic and renal activities. Incubation of the S9 fraction prepared from the jejunum with testosterone and NADPH resulted in the formation of 2α-, 6α-, 6β- and 16α-hydroxytestosterone and androstenedione at rates that were 1.6, 24, 1.3, 0.6 and 1.3%, respectively, of the corresponding hepatic values. The production of 2α-hydroxytestosterone was catalyzed only by the preparations from the duodenum and jejunum; whereas 6α-, 6β- and 16α-hydroxytestosterone and androstenedione were produced in all regions of the intestine. In the case of the rat kidney, the rates of formation of the different testosterone metabolites were between 0.6 and 35% of the corresponding liver activity. The activity of glutathione transferase was approximately 12–26% of the corresponding hepatic activity throughout the intestine. The highest activity of phenol sulfotransferase was observed in the lower colon (almost 6% of the liver activity) and the lowest activity in the duodenum (1%). The renal activities of GST and pST were 70 and 1%, respectively, of the corresponding liver values. In summary, the metabolism of testosterone and the activities of GST and pST in rat intestine are generally low to very low in comparison to the corresponding activities in rat liver. In most cases, these activities are present throughout the entire intestine and not restricted to a particular portion(s) of this organ.

Synergistic effect of antioxidant phenolic acids on human phenolsulfotransferase activity.

Sulfate conjugation by phenolsulfotransferases (PSTs) is an important process in the detoxification of xenobiotics and endogenous compounds. There are two forms of PSTs for the sulfation of small phenols (PST-P) and monoamines (PST-M). Phenolic acids are known to increase the activities of PST-P and PST-M. The purpose of this study is to investigate the synergistic effect of the combinations of phenolic acids on human PSTs activities. The combinations of p-hydroxybenzoic acid, gentisic acid, ferulic acid, gallic acid, and coumaric acid in a random order for their effects on PSTs activities were evaluated at concentrations of 2.5, 5.0, and 7.5 microM. The PST-M activity was significantly increased when gentisic acid was combined with each of the other phenolic acids. When p-hydroxybenzoic acid was combined with each of the other phenolic acids, a synergistic effect with respect to the promotion of PST-P activity was obtained. A potential synergistic effect for the PST-P activity was also found in the following combination: p-hydroxybenzoic acid + gallic acid + gentisic acid, p-hydroxybenzoic acid + gallic acid + m-coumaric acid, p-hydroxybenzoic acid + o-coumaric acid + p-coumaric acid, p-hydroxybenzoic acid + o-coumaric acid + m-coumaric acid, gallic acid + gentisic acid + p-coumaric acid, and gallic acid + o-coumaric acid + m-coumaric acid. Therefore, the activities of both forms of PSTs can be promoted by all of these combinations of phenolic acids. These results provide a better understanding regarding the effect of phenolic acids on human PSTs activities, as well as more information on the intake of antioxidant phenolic acids for human health.

Phytoestrogens are potent inhibitors of estrogen sulfation: implications for breast cancer risk and treatment.

We investigated the ability of 37 flavonoids and flavonoid sulfoconjugates, including some abundant dietary constituents, to act as substrates and/or inhibitors of the sulfotransferase and sulfatase enzymes that interconvert active estrogens and inactive estrogen sulfates in human tissues. The enzymes studied include estrogen sulfotransferase, the thermostable phenolsulfotransferase that acts on a range of substrates including estrogens; steroid sulfatase; and two related enzymes, monoamine phenolsulfotransferase and arylsulfatase A. Several dietary flavonoids, including the soy isoflavones genistein and daidzein, were sulfated by these human sulfotransferases. Many flavonoids were potent inhibitors of thermostable phenolsulfotransferase. Genistein and equol were potent mixed inhibitors of hepatic estrogen sulfotransferase, with inhibitory constant values of 500 nM and 400 nM, respectively. Monoamine phenolsulfotransferase activity was relatively unaffected by flavonoids, but this enzyme was mainly responsible for the sulfation of flavonoids at concentrations greater than 1 micro M. Of the compounds tested, only daidzein 4,7-bisulfate, a trace metabolite in humans, significantly inhibited steroid sulfatase in the micromolar concentration range. Hence, dietary flavonoids may be able to influence the bioavailability of endogenous estrogens, and disrupt endocrine balance, by increasing the ratio of active estrogens to inactive estrogen sulfates in human tissues.

Activities of drug metabolizing enzymes in bovine colon epithelial cell cultures.

The metabolic competence of cultured bovine colon epithelial cells was evaluated by determining activities of phase I and II enzymes in colonocytes cultured for different intervals (maximum of 10 days) compared with activities measured in freshly isolated cells. Cytochrome p50 1A1-associated 7-ethoxyresorufin O-deethylase (EROD) activity was detectable in freshly isolated colonocytes and in colon cells maintained in culture for up to 5 days. In contrast to liver samples, cytochrome p50 3A4-associated 7-benzyloxyresorufin O-debenzylase (BROD) activity was not detectable in bovine colon cells. Prostaglandin H synthase-mediated production of prostaglandin E(2) was found in freshly isolated and also in cultured colonocytes. Both isoenzymes (COX 1 and COX 2) were detected in cultured cells. To examine phase II metabolic potency, activities of N-acetyltransferases 1 and 2, of phenol and amino sulfotransferases, of glutathione S-transferases alpha, mu, pi and theta and of UDP-glucuronyltransferase were measured. N-Acetyltransferase (NAT) activity (substrate p-aminobenzoic acid, PABA, a diagnostic substrate for the human NAT-1 enzyme) was stable under culture conditions and during the observed culture period comparable to that of freshly isolated cells. In contrast, sulfamethazine, a specific substrate for NAT-2, was not acetylated, neither in bovine colon cells nor in bovine liver samples. Whereas activity of amino sulfotransferase (substrate 2-naphthylamine) decreased continuously during the entire culture period, the activity of phenol sulfotransferase (substrate 1-naphthol) decreased only slowly. Activity of total glutathione S-transferases (alpha, mu, and pi) (substrate 1-chloro-2,4-dinitrobenzene) decreased after 2 days in culture, but was stable during the following culture period. Activity of glutathione S-transferase theta (substrate epoxy-3-nitrophenoxypropane) changed during the culture period. At the beginning and the end (after 10 days) of the culture period maximum activity was measured. Activity of UDP-glucuronyltransferase increased during the culture period reaching a maximum after 7 days. The results show that cultured bovine epithelial colon cells express several enzyme activities required for the biotransformation of xenobiotics.

Mechanism of posttranslational regulation of phenol sulfotransferase: expression of two enzyme forms through redox modification and nucleotide binding.

Sulfotransferase catalyzes sulfuryl group transfer between a nucleotide and a variety of nucleophiles that may be sugar, protein, xenobiotics, and other small molecules. Nucleotides may serve as cosubstrate, cofactor, inhibitor, or regulator in an enzyme catalyzed sulfuryl group transfer reaction. We are trying to understand how nucleotide regulates the activity of phenol sulfotransferase (PST) through the expression of two enzyme forms. The homogeneous rat recombinant PST was obtained from Escherichia coli, and the nucleotide copurified was examined. The nucleotide was completely removed from inactive PST in high salt and oxidative condition. Total enzyme activity was recovered following incubation in reductive environment. Many nucleotides are known to tightly bind to PST but only one nucleotide, 3'-phosphoadenosine 5'-phosphate (PAP), was identified to combine with PST by ion-pair RP-HPLC, UV-visible spectra, (31)P NMR, and ESI-MS and MS-MS spectrometry. In addition to the presence or absence of PAP, oxidation following reduction of PST was required to completely interconvert the two forms of PST. According to the experimental results, a mechanism for the formation of the two enzyme forms was proposed.

Structure-Function Relationships in the Stereospecific and Manganese-dependent 3,4-Dihydroxyphenylalanine/ Tyrosine-sulfating Activity of Human Monoamine-form Phenol Sulfotransferase, SULT1A3

The human monoamine-form phenol sulfotransferase (PST), SULT1A3, has a unique 3,4-dihydroxyphenylalanine (Dopa)/tyrosine-sulfating activity that is stereospecific for their d-form enantiomers and can be stimulated dramatically by Mn(2+). This activity is not present in the simple phenol-form PST, SULT1A1, which is otherwise >93% identical to SULT1A3 in amino acid sequence. The majority of the differences between these two proteins reside in two variable regions of their sequences. Through the characterization of chimeric PSTs where these two regions were exchanged between them, it was demonstrated that variable Region II of SULT1A3 is required for the stereospecificity of its Dopa/tyrosine-sulfating activity, whereas variable Region I of SULT1A3 is required for the stimulation by Mn(2+) of this activity. Further studies using point-mutated SULT1A3s mutated at amino acid residues in these two regions and deletional mutants missing residues 84-86 and 84-90 implicate residue Glu-146 (in variable Region II of SULT1A3), as well as the presence of residues 84-90 of variable Region I, in the stereospecificity in the absence of Mn(2+). Residue Asp-86 (in variable Region I of SULT1A3), on the other hand, is critical in the Mn(2+) stimulation of the Dopa/tyrosine-sulfating activity of SULT1A3. A model is proposed, with reference to the reported x-ray crystal structure of SULT1A3, to explain how the normal role of SULT1A3 in dopamine regulation may be subverted in the presence of Mn(2+). These studies could be relevant in understanding the stereoselective action of SULT1A3 on chiral drugs.

Manganese Stimulation and Stereospecificity of the Dopa (3,4-Dihydroxyphenylalanine)/Tyrosine-sulfating Activity of Human Monoamine-form Phenol Sulfotransferase: KINETIC STUDIES OF THE MECHANISM USING WILD-TYPE AND MUTANT ENZYMES

Kinetic studies were performed to dissect the mechanism underlying the remarkable Mn(2+) stimulation of the Dopa/tyrosine-sulfating activity of the human monoamine (M)-form phenol sulfotransferase (PST). The activities and the stimulation by Mn(2+) are highly stereospecific for the d-form enantiomers of tyrosine and Dopa. Analysis of the kinetic results strongly suggests that tyrosine-Mn(2+) and tyrosine-Mn(2+)-tyrosine complexes are obligatory substrates, whereas Dopa-Mn(2+) complexes may be better substrates than Dopa alone. This activation of the Dopa/tyrosine-sulfating activity of M-form PST by Mn(2+) via complex formation between Mn(2+) and the substrate is the first reported case of a regulatory mechanism in this important class of enzymes. Our previous studies using point-mutated M-form PSTs established that the Mn(2+) (in the substrate-Mn(2+) complex) exerts its stimulatory effect by binding predominantly to the Asp-86 residue at the active site. We present here further studies using dopamine as substrate to bolster this conclusion. The possible physiological implications of this rather unusual specificity for the d-amino acid and its derivatives and the stimulation by Mn(2+) are discussed in the context of protective and detoxification mechanisms that may operate in neurodegenerative processes in the brain. The Mn(2+) stimulation of the activity of M-form PST toward d-enantiomers of Dopa/tyrosine may have implications for other substrates (including chiral drugs) and for the other cytosolic sulfotransferases that are involved in the regulation of endogenous metabolites as well as in detoxification.

Effects of Phenolic Environmental Estrogens on the Sulfotransferase Activity of the Mouse Intestine and a Human Colon Carcinoma Cell Line, Caco-2.

In order to explore the possible role of sulfation in the inactivation of environmental estrogens at gastrointestinal sites and their subsequent removal, we investigated the effects of phenolic environmental estrogens on sulfotransferase (ST) activity. The mouse intestine and a human colon carcinoma cell line, Caco-2, were studied. ST enzymes were found to have a high affinity for diethylstilbestrol (DES) and bisphenol A (BPA), whereas phenol ST (PST) activity was strongly inhibited by nonylphenol and genistein in both mice and humans. Kinetic analysis showed that this inhibition was competitive. These observations suggest that nonylphenol and genistein compounds might inhibit PST activity in the human intestine and that they might escape detoxification by sulfation.

Epigallocatechin Gallate (EGCG) Inhibits the Sulfation of 1-Naphthol in a Human Colon Carcinoma Cell Line, Caco-2.

We have previously reported that epigallocatechin gallate (EGCG) strongly inhibits the in vitro phenol sulfotransferase (P-ST) activity of a human colon carcinoma cell line, Caco-2. In the present study, we examined the ability of EGCG to inhibit the sulfation of 1-naphthol in intact Caco-2 cells. Sulfation of 1-naphthol was detected in Caco-2 cells after 2 h of incubation, and was observed to continue for 24 h, resulting in an accumulation of sulfated 1-naphthol. Sulfation was strongly inhibited by the addition of EGCG to the culture medium. The IC50 of EGCG was calculated to be 20 microM; this value is similar to that obtained from in vitro assays (14 microM) [Ref. Tamura et al., Biol. Pharm. Bull., 23, 695, (2000)]. These results indicate that catechins are capable of inhibiting P-ST activity in intact cells as well as in vitro. We believe that the inhibitory activity of catechins might be the mechanism by which catechins (and green tea) exert anti-carcinogenic activity against procarcinogenic compounds that require P-ST activation in vivo.

Nucleotide Binding and Sulfation Catalyzed by Phenol Sulfotransferase

The sulfation of a nucleotide is an indispensable step for the sulfuryl group transfer in a biological system. The product and cosubstrate of sulfotransferase in physiological condition are adenosine 3′,5′-bisphosphate (PAP) and 3′-phospho adenosine 5′-phosphosulfate (PAPS), respectively. We find that ribose and adenine, two major parts of the adenosine nucleotide, bind tightly to phenol sulfotransferase (PST) separately, and various nucleotides also bind tightly to PST. We determine the dissociation constants of a variety of nucleotides and examine their potential as cofactors or cosubstrates of PST. Using 4-nitrophenyl sulfate as the sulfuryl group donor, three nucleotides, adenosine 5′-monophosphate (AMP), adenosine 2′,5′-bisphosphate (2′,5′-PAP), and adenosine 2′:3′-cyclic phosphate 5′-phosphate (2′:3′-cyclic PAP), are shown here for the first time to be sulfated at 5′-phopho position by a PST catalyzed reaction. Spectrophotometry, HPLC, and 31P NMR are used to determine the activity of PST and identify the sulfated nucleotides. The Vmax of PST and Km of these nucleotides are determined when they are used as cofactors or cosubstrates for the sulfuryl group transfer. The existence and possible physiological significance of these newly reported binding and sulfation of nucleotides by PST in biology is yet to be discovered.

Inhibitory effects of green tea and grape juice on the phenol sulfotransferase activity of mouse intestines and human colon carcinoma cell line, Caco-2.

Tea and fruit juices are beverages consumed daily all over the world. The present study reports the inhibitory effects of these beverages on the activity of mammalian intestinal phenol sulfotransferases (P-STs). Green tea strongly inhibited the E. coli-expressed mouse intestinal P-ST activity in vitro. (-)-Epigallocatechin gallate (EGCG) was found to be the most potent inhibitor among the catechins tested (IC50=0.93 microM). (-)EGCG also inhibited the P-ST activity of the human colon carcinoma cell line, Caco-2. Kinetic analysis showed that the inhibition was competitive. Among fruit juices examined (apple, grape, grapefruit and orange), grape juice exhibited the most potent inhibitory action on the P-ST activity of mouse intestines and human colon carcinoma cells. The inhibitory activity of grape juice was located mainly in the skin and seeds. Flavonols, such as quercetin and kaempferol, inhibited the P-ST activity at low concentrations. These observations suggest the possible inhibition of P-ST activity in human intestines by green tea or grape juice.

Interethnic and interindividual variabilities of platelet sulfotransferases activity in Italians and Finns.

The aim of this investigation was to see whether there was interethnic variability in the platelet activities of catechol- and phenol sulfotransferases in Italians and Finns. The activities of catechol- and phenol sulfotransferases were measured in platelets obtained from 103 Italian and 74 Finnish individuals. Blood donors were obtained from healthy volunteers free from drugs and without apparent disease. The activities of catechol- and phenol sulfotransferases were measured with 60 microM dopamine and 4 microM 4-nitrophenol as substrates, respectively. The activity of catechol sulfotransferase was not gender dependent and the median estimates (pmol/min/mg) were 9.10 in Italians and 6.37 in Finns (P = 0.0018). The activity of phenol sulfotransferase activity was gender dependent in Finns but not in Italians. The median estimates (pmol/min/mg) were 3.81 in Finnish men and 1.18 in Finnish women (P = 0.0007). In Italian men and women, the median estimates (pmol/min/mg) of phenol sulfotransferase activity were 1.25 and 1.24, respectively (NS). This study shows that platelet catechol sulfotransferase activity is greater in Italians than Finns and that the activity of phenol sulfotransferase is gender regulated in Finns but not in Italians. Thus, interethnic differences exist in platelet sulfotransferases between Italians and Finns.