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At least 19 recordsLinked to original sources
PubMed2002

Arylsulfotransferase from Clostridium innocuum-A new enzyme catalyst for sulfation of phenol-containing compounds.

Arylsulfotransferase (AST, EC 2.8.2.22), an enzyme capable of sulfating a wide range of phenol-containing compounds was purified from a Clostridium innocuum isolate (strain 554). The enzyme has a molecular weight of 320 kDa and is composed of four subunits. Unlike many mammalian and plant arylsulfotransferases, AST from Clostridium utilizes arylsulfates, including p-nitrophenyl sulfate, as sulfate donors, and is not reactive with 3-phosphoadenosine-5'-phosphosulfate (PAPS). The enzyme possesses broad substrate specificity and is active with a variety of phenols, quinones and flavonoids, but does not utilize primary and secondary alcohols and sugars as substrates. Arylsulfotransferase tolerates the presence of 10 vol% of polar cosolvents (dimethyl formamide, acetonitrile, methanol), but loses significant activity at higher solvent concentrations of 30-40 vol%. The enzyme retains high arylsulfotransferase activity in biphasic systems composed of water and nonpolar solvents, such as cyclohexane, toluene and chloroform, while in biphasic systems with more polar solvents (ethyl acetate, 2-pentanone, methyl tert-butyl ether, and butyl acetate) the enzyme activity is completely lost. High yields of AST-catalyzed sulfation were achieved in reactions with several phenols and tyrosine-containing peptides. Overall, AST studied in this work is a promising biocatalyst in organic synthesis to afford efficient sulfation of phenolic compounds under mild reaction conditions.

Animals↗
PubMed1987

Immobilized arylsulfotransferase.

Arylsulfotransferase was stabilized for storage more markedly by covalent immobilization onto DEAE-cellulose or DEAE-Sephadex. The optimal pH, Km for sulfate donor and thermostability of covalently immobilized arylsulfotransferase were similar to those of the free enzyme. Tyrosine-containing peptides such as cholecystokinin-8-nonsulfate, tyrosine methylester and (Leu)enkephalin as acceptor substrates were effectively sulfated by the immobilized enzyme.

Arylsulfotransferase↗
PubMed1981

Stimulation of arylsulfotransferase activity by progestins in human endometrium in vitro.

The effect of progestin on the rate of estradiol (E2) sulfurylation in human endometrium was studied in two culture systems: 1) in intact endometrial tissue fragments and 2) in isolated endometrial epithelial glands and stromal cells. Human endometrial tissue fragments were cultured in medium in the presence and absence of progesterone (P) for 24-48 h. The arylsulfotransferase activity was determined in the cytosol of the tissue homogenate by measuring the rate of conversion of E2 to E2-3 sulfate (E2S) in the presence of an excess amount of substrate and cofactor (adenosine-3'-phosphate-5'-phosphosulfate). The enzyme activity was found to be stimulated in the sample cultured with P. The increase in activity correlated with the dose of P and period of culture. Stimulation of endometrial estradiol dehydrogenase activity by P, which has been reported in a series of previous publications, was also evident in the current study. Human endometrial glandular epithelial and stromal cells were cultured separately in medium in the presence and absence of medroxyprogesterone acetate (MPA). The cultured cells were incubated with E2 (0.4-0.6 nM) for 2 h. The formation of estrogen sulfates, [estrone sulfate (E1S) and E2S] was greatly increased in all the proliferative glandular epithelial cells cultured with MPA. However, the rate of sulfurylation was not appreciably affected by MPA in stromal cells and in glandular epithelial cells from secretory endometrium. The oxidation of E2 in these cultured cells was also influenced by P but not to the extent of sulfurylation. These results indicate that arylsulfotransferase in endometrium originates from glandular epithelial cells and can be stimulated by progestin.

Arylsulfotransferase↗
PubMed1990

Enzymatic sulfation of quercetin by arylsulfotransferase from a human intestinal bacterium.

A novel type of arylsulfotransferase was partially purified from human intestinal bacteria and its enzymatic properties were examined. Polyphenols such as chalcone, xanthone and flavonoid were found to be sulfated by the bacterial arylsulfotransferase though the sulfation activity varied depending upon the positions of the hydroxyl groups. Quercetin, as an example of a flavonol, was rapidly sulfated when p-nitrophenyl sulfate (PNS) was taken as a donor substrate. At a ten-fold molar excess of PNS over quercetin, two products, the 3,3'-disulfate and 3,3',7-trisulfate derivatives, were formed, but the 4'- and 5-hydroxyl groups were not sulfated. In the case of equimolar or two-fold molar excess of PNS to quercetin, only the 3,3'-disulfate was produced and no monosulfate was formed. The enzymatic procedure is useful as a specific and convenient method for the preparation of polyphenol sulfate esters.

Arylsulfotransferase↗
PubMed1991

Enzymatic sulfation of polyphenols related to tannins by arylsulfotransferase.

This report discusses a novel type of arylsulfotransferase (AST) which was derived from human intestinal bacterium sulfated polyphenolic compounds when p-nitrophenyl sulfate (PNS) was taken as a donor substrate. (+)-Catechin, (+/-)-catechin, (-)-epicatechin and (-)-epicatechin gallate were better substrates than tyramine. (-)-Epigallocatechin and (-)-epigallocatechin gallate were slightly worse substrates than tyramine. Although gallic acid was a bad substrate, alkyl gallate esters were better substrates than tyramine. The degree of acceptor specificity increased in proportion to the length of the alkyl group up to the carbon number of five. Pedunculagin, geraniin and corilagin were less effective than tyramine. Rosmarinic acid and penta-O-galloyl-beta-D-glucose were similarly well sulfated. Two products, 4'-monosulfate and 4',5-disulfate of (+)-catechin, were detected at a two-fold molar excess of PNS over (+)-catechin. When (+)-catechin-4'-monosulfate as an acceptor was enzymatically sulfated with PNS as a donor, only the 4',5-disulfate was produced. Thus, arylsulfotransferase was useful for the convenient preparation of sulfate esters of polyphenols at their specific hydroxyl groups.

Arylsulfotransferase↗
PubMed1986

Purification, characterization and reaction mechanism of novel arylsulfotransferase obtained from an anaerobic bacterium of human intestine.

A novel type of arylsulfotransferase was purified from Eubacterium A-44, one of the predominant bacteria of human intestine. The enzyme (Mr 315 000) was composed of four identical subunits (Mr 80 000) whose N-terminal amino acids were arginine. pI and optimal pH of the enzyme were 3.9 and 8-9, respectively. The apparent Km for p-nitrophenylsulfate using tyramine as an acceptor substrate and that for tyramine using p-nitrophenylsulfate as a donor substrate were determined to be 0.104 mM and 3.5 mM, respectively. The reaction mechanism of the enzyme was proposed as follows: a donor substrate, p-nitrophenyl [35S]sulfate, combines a histidine residue of the enzyme active site with concomitant release of a phenolic compound, p-nitrophenol. The sulfate group of the histidine residue transfers to a tyrosine group, and then to an acceptor with the binding of another donor to the histidine residue.

Arginine↗
PubMed2003

Mechanistic studies of beta-arylsulfotransferase IV.

Sulfotransferases are an important class of enzymes that catalyze the transfer of a sulfuryl group to a hydroxyl or amine moiety on various molecules including small-molecule drugs, steroids, hormones, carbohydrates, and proteins. They have been implicated in a number of disease states but remain poorly understood, complicating the design of specific, small-molecule inhibitors. A linear free-energy analysis in both the forward and reverse directions indicates that the transfer of a sulfuryl group to an aryl hydroxyl group catalyzed by beta-arylsulfotransferase IV likely proceeds by a dissociative (sulfotrioxide-like) mechanism. Values for the Brønsted coefficients (beta(nuc) and beta(lg)) are +0.33 and -0.45, giving Leffler alpha values of 0.19 and 0.61 for the forward and reverse reactions, respectively.

Amino Acid Sequence↗
PubMed1990

Pharmacological activities of synthetic human cholecystokinin-33 of which tyrosine was sulfated by arylsulfotransferase.

The pharmacological activities of synthetic human CCK-33, in which a tyrosine molecule was sulfated by arylsulfotransferase, were investigated in the rat and the guinea-pig. The activities were compared with those of non-sulfated CCK-33 (CCK-33NS), CCK-8 and CCK-4. CCK-33 was about 100 fold more potent than non-sulfated CCK-33(CCK-33NS) but was about 20 fold less potent than CCK-8 in the contraction of the isolated gallbladder of the guinea-pig. In rat pancreatic secretion, intravenous CCK-33 and CCK-8 showed almost the same activity. The potency of each was about 1000 fold more than the individual potency of CCK-33NS, non-sulfated CCK-8 (CCK-8NS) and CCK4. There were no significant differences in gastric acid stimulatory activities among CCK-33, CCK-8, CCK-4, but the activities of CCK-33NS and CCK-8NS were less than those of CCK-33 and CCK-8, respectively. CCK-33 and CCK-8 produced a reduction in the intake of powder chow in doses of 10(-8) and 3 x 10(-8) mol/kg i.p., but CCK-33NS, CCK-8NS and CCK-4 did not. In conclusion, the activities of synthetic human CCK-33 are almost the same as those of CCK-8 on exocrine pancreatic secretion, gastric acid secretion and food intake, but less than CCK-8 on isolated gallbladder contraction.

Animals↗
PubMed2000

Purification, cloning, and characterization of an arylsulfotransferase from the anaerobic bacterium Eubacterium rectale IIIH.

A bacterium, Eubacterium rectale IIIH, which possessed arylsulfotransferase (ASST) activity was isolated from human feces. The ASST gene (astA) was cloned and the corresponding protein partially characterized. This gene shows only moderate homology to the previously sequenced ASST genes of Klebsiella and Enterobacter, which are very closely related to each other.

Journal Article↗
PubMed1994

Activation of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b] pyridine by cDNA-expressed human and rat arylsulfotransferases.

Sulfation plays an obligatory role in the activation of N-hydroxy derivatives of carcinogenic arylamine (amide)s and heterocyclic amines. We found that the hepatic sulfotransferase-mediated covalent binding of 3H-labeled 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b] pyridine (N-OH-PhIP) to calf thymus DNA was 3.3 and 12.9 times higher with human cytosol preparation than with male and female rat cytosol preparations, respectively, in the presence of 3'-phosphoadenosine 5'-phosphosulfate. To assess the activating capacities of individual phenol-sulfating sulfotransferases, five different forms, human ST1A2 and ST1A3 and rat ST1A1, ST1B1 and ST1C1, were expressed in heterologous cells. All five sulfotransferases mediated the activation of N-OH-PhIP to DNA-bound products. The extents of the binding, however, differed considerably among these forms. Human ST1A2 and ST1A3 mediated the activation of N-OH-PhIP at 5.2- and 6.2-fold higher rates than did rat ST1C1, a main N-hydroxy-2-acetylaminofluorene-activating sulfotransferase, in rat liver. Extents of the binding of N-OH-PhIP in human hepatic cytosols of different individuals were positively correlated with the contents of immunoreactive ST1A2/3. These results suggest a potential role of human liver sulfotransferases in N-OH-PhIP activation. In contrast, the low sulfotransferase-mediated activation of N-OH-PhIP in rat liver is consistent with the lack of PhIP hepatocarcinogenicity in this species.

Amino Acid Sequence↗
PubMed1991

Modulation of hepatic mRNA translation activity and specific expression of arylsulfotransferase IV during acetylaminofluorene-induced rat hepatocarcinogenesis.

Enzymatic sulfation of N-hydroxylated arylamines by mammalian hepatic cytosol sulfotransferases (AST; EC 2.8.2.1) is an important metabolic step which generates ultimate carcinogens. The metabolic activity of AST IV, the putative isozymic form of AST primarily responsible for catalyzing N-hydroxy-2-acetylaminofluorene sulfation, is modulated during 2-acetylaminofluorene (AAF)-induced rat hepatocarcinogenesis. To characterize the molecular mechanisms regulating the differential expression of AST IV, we have assessed polyadenylated mRNA derived from the livers of Sprague-Dawley rats undergoing different stages of AAF hepatocarcinogenesis for general in vitro translation capacity and specific expression of AST IV and albumin. Following 1 and 3 cycles of a cyclical feeding regimen (3 weeks 0.05% AAF, then 1 week basal diet), the mRNA capacity for translation was lowered and the expression of AST IV and albumin was down-regulated about 2-fold each but recovered to normal levels when treated rats were subsequently placed on basal diet for 3 continuous weeks. Cytosolic albumin levels were determined by Western blot analysis to be lowered about 1.5-2-fold. In contrast, however, mRNA from rats on basal diets for 3 weeks subsequent to cycle 5 of the feeding regimen recovered only about 50% of the capacity for AST IV expression, although overall translation capacity and albumin expression returned to normal levels. This pattern of reversible expression, followed by irreversible expression of AST IV at early and late stages of AAF hepatocarcinogenesis, respectively, provides the first evidence correlating the modulation of hepatic mRNA capacity for AST IV expression with differential cytosolic AST IV activity in the AAF hepatocarcinogenesis model. The results further suggest that during early stages in hepatocarcinogenesis modulation of mRNA protein synthesis functions may be a critical factor in AAF-mediated lowering of AST IV expression, while other persistent genetic lesions are likely playing a more significant role at the late stages of the carcinogenic process leading to neoplastic transformation of initiated hepatocytes.

2-Acetylaminofluorene↗
PubMed1990

2-Acetylaminofluorene-mediated alteration in the level of liver arylsulfotransferase IV during rat hepatocarcinogenesis.

Rat liver cytosolic sulfotransferase activity forms the highly reactive sulfuric acid ester of N-hydroxy-2-acetylaminofluorene (N-OH-2AAF), an ultimate carcinogen in 2-acetylaminofluorene (2AAF) hepatocarcinogenesis. A previous report demonstrated that 2AAF-induced liver hyperplastic nodules displayed a persistent loss of cytosolic N-OH-2AAF sulfotransferase activity following a hepatocarcinogenesis-producing regimen of 2AAF administration. As an initial step in examining the mechanism responsible for lowering N-OH-2AAF sulfotransferase activity, a monospecific polyclonal antibody to aryl sulfotransferase IV (AST IV) was produced and used in the assessment of AST IV as a candidate enzyme for liver cytosolic N-OH-2AAF sulfotransferase activity. Studies comparing the levels of N-OH-2AAF sulfotransferase activity of highly purified AST IV and rat liver cytosols with corresponding immunochemical analysis of AST IV contents demonstrated that there was sufficient AST IV activity in liver cytosols to indicate that it was the primary enzyme catalyzing cytosolic N-OH-2AAF sulfation. A subsequent immunochemical survey of nine extrahepatic tissues showed no detectable AST IV content and indicated that AST IV expression may be tissue specific. An immunochemical comparison of AST IV levels in control liver cytosols (high in sulfotransferase activity) with cytosols from 2AAF-derived hyperplastic nodules (low in sulfotransferase activity) or liver tumors (no sulfotransferase activity) showed low or no detectable levels, respectively, of AST IV. In addition, an immunochemical analysis of four rat hepatoma cell lines showed they contained no detectable levels of AST IV. These results suggested a strong correlation existed between a decrease in AST IV expression and tumor development. When the liver cytosols of rats taken from early, intermediate, and late stages of 2AAF carcinogenesis were analyzed for the development of a persistent loss of N-OH-2AAF sulfotransferase activity, a parallel loss of cytosolic N-OH-2AAF sulfotransferase activity and AST IV content was observed in rats which had proceeded from a stage of low risk to high risk for liver cancer. These findings indicated that (a) AST IV, a liver-specific enzyme, was the principle enzyme comprising cytosolic N-OH-2AAF sulfotransferase activity and (b) the decrease in sulfotransferase activity in nodules and tumors resulted from a decrease in the level of AST IV expression. Furthermore, it is suggested that a persistent decrease in AST IV expression may reflect a role for AST IV as part of a resistance phenotype in which transforming liver cells are able to escape the cytotoxic effects of highly reactive 2AAF metabolites and progress to cancer.

2-Acetylaminofluorene↗
PubMed1986

The role of intestinal flora in metabolism of phenolic sulfate esters.

Arylsulfotransferase activity was found in the feces of human (14.74 +/- 2.674) and rat (7.37 +/- 1.126 mumol/hr/g wet feces). In the case of the rat, arylsulfotransferase activity was markedly and rapidly decreased by the treatment with antibiotics mixture, but restored to the original activity 3 weeks after stopping the administration of antibiotics. The excretion of the sulfate esters derived from p-nitrophenylsulfate was enhanced by the administration of acetaminophen but not by the treatment with antibiotics. Furthermore, in rats treated with antibiotics, inorganic sulfate excretion was severely decreased. When only acetaminophen was administered, the excretion of acetaminophen-O-sulfate showed a 10-15% decrease in rats treated with antibiotics compared with conventional rat.

Acetaminophen↗
PubMed1992

Inhibition of sulfotransferase affecting unscheduled DNA synthesis induced by 2-acetylaminofluorene: an in vivo and in vitro comparison.

The unscheduled DNA repair (UDS) assay was conducted using the in vivo and in vitro procedures to investigate the role of arylsulfotransferases (AST) in the genotoxicity of 2-acetylaminofluorene (AAF). The in vivo assay had 4 groups of rats that consisted of those treated with pentachlorophenol (PCP), PCP and AAF, or AAF and an untreated control. The in vitro assay used hepatocytes from 3-methylcholanthrene or corn oil (control) treated rats. In both the in vivo and in vitro UDS assays AAF induced DNA damage. PCP, an inhibitor of arylsulfotransferase, significantly decreased AAF induced DNA damage. In the in vivo assay, PCP induced a significant increase in UDS and confounded an investigation of the role of sulfotransferase. The in vitro UDS assay more clearly defined the effect of PCP on AAF genotoxicity.

2-Acetylaminofluorene↗
PubMed2002

How sleep deprivation affects gene expression in the brain: a review of recent findings.

The identification of the molecular correlates of sleep and wakefulness is essential to understand the restorative processes occurring during sleep, the cellular mechanisms underlying sleep regulation, and the functional consequences of sleep loss. To determine what molecular changes occur in the brain during the sleep-waking cycle and after sleep deprivation, our laboratory is performing a systematic screening of brain gene expression in rats that have been either sleeping or spontaneously awake for a few hours and in rats that have been sleep deprived for different periods of time ranging from a few hours to several days. So far, ~10,000 transcripts expressed in the cerebral cortex have been screened. The expression of the vast majority of these genes does not change either across behavioral states or after sleep deprivation, even when forced wakefulness is prolonged for several days. A few hours of wakefulness, either spontaneous or forced by sleep deprivation, increase the expression of the same small groups of genes: immediate-early genes/transcription factors, genes related to energy metabolism, growth factors/adhesion molecules, chaperones/heat shock proteins, vesicle- and synapse-related genes, neurotransmitter/hormone receptors, neurotransmitter transporters, and enzymes. Sleep, on the other hand, induces the expression of a few unknown transcripts whose characterization is in progress. Thus, although the characterization of the molecular correlates of behavioral states is not yet complete, it is already apparent that the transition from sleep to waking can affect basic cellular functions such as RNA and protein synthesis, neural plasticity, neurotransmission, and metabolism. The pattern of changes in gene expression after long periods of sleep deprivation is unique and does not resemble that of short-term sleep deprivation or spontaneous wakefulness. A notable exception is represented, however, by the enzyme arylsulfotransferase, whose induction appears to be proportional to the duration of previous wakefulness. Arylsulfotransferase in rodents plays a major role in the catabolism of catecholamines, suggesting that an important role for sleep may be that of interrupting the continuous activity, during wakefulness, of brain catecholaminergic systems.

Animals↗
PubMed1998

Nonlinearities in 2-acetylaminofluorene exposure responses for genotoxic and epigenetic effects leading to initiation of carcinogenesis in rat liver.

The dose responses for several effects of low-level limited exposures to 2-acetylaminofluorene (AAF) in the livers of male Fischer 344 rats were measured and a subsequent phenobarbital tumor promotion regimen was used to manifest initiation of carcinogenesis. Three doses over a 10-fold range yielding cumulative total exposures of 0.126, 0.42, and 1.26 mmol AAF/kg body weight were achieved by daily intragastric instillation for up to 12 weeks with interim terminations. This was followed by 24 weeks administration of 500 ppm phenobarbital (PB) in the diet to promote liver tumor development. At 12 weeks at the end of AAF administration, all exposures produced adducts in liver DNA, measured by 32P postlabeling, and the level of adducts increased with exposure, except that the high exposure did not produce a dose proportional increase. Measurement of arylsulfotransferase activity, a key enzyme in the metabolic activation of AAF, revealed that in livers from the high exposure animals, the enzyme was inhibited. To assess for toxicity, the centrilobular zone of glutamine synthetase-positive hepatocytes was quantified immunohistochemically at 12 weeks. The area of the zone was reduced in the high exposure group and there was a trend to reduction in relationship to exposure. The two lower exposures to AAF produced no increase in cell proliferation, whereas the high exposure resulted in a marked increase, about 8-fold over controls. Initiation was assessed by induction of hepatocellular altered foci (HAF) that expressed the placental form of glutathione S-transferase. AAF induced HAF in the high exposure group, 9-fold at 8 weeks and 170-fold at 12 weeks compared to controls. In rats maintained on PB for 24 weeks after exposure, the multiplicity of HAF increased in controls and comparably in the low and mid exposure groups, but remained at the about the same high level in the high exposure group. The high exposure produced a substantial incidence of benign neoplasms by 12 weeks, and with promotion by 36 weeks, all rats developed hepatocellular neoplasia. In the mid exposure group, only one adenoma occurred at 36 weeks in 17 rats, while in the low exposure group, no liver tumor occurred in 23 rats. Thus, these findings document nonlinearities for some of the effects of AAF, with supralinear effects at the high exposure for cell proliferation and induction of HAF, and a no-observed-effect level for induction of promotable liver neoplasms at the lowest cumulative exposure of 0.126 mmol/kg, in spite of the formation of DNA adducts. We conclude that the effects of this DNA-reactive hepatocarcinogen leading to initiation exhibit nonlinearities and possible thresholds.

2-Acetylaminofluorene↗