Bile salt sulfotransferase in guinea pig liver

Bile salt sulfotransferase from guinea pig liver is purified by the procedures of ammonium sulfate fractionation, Sephadex G-100 column chromatography, agarose-hexane-adenosine 3′,5′-diphosphate affinity chromatography and polyacrylamide gel electrophoresis. The purified enzyme exhibits a pH optimum of 6.8, an isoelectric point of 5.6 and a molecular weight of 7600 estimated by gel filtration technique. The apparent K_m values of the enzyme are 7.7·10^?5 M for taurolithocholate and 1.4·10^?6 M for 3′-phosphoadenosine 5′-phosphosulfate. It requires Mg²⁺ and free sulfohydryl group(s) for activity. The enzyme reacts with hydroxy groups of bile salts at both 3α and 3β positions. No activity is found in the kidney of guinea pig. The purified enzyme does not react with estrone, estradiol, testosterone, dehydroepiandrosterone, cholesterol, phenol, tyramine, and serotonin. The results indicate that bile salt sulfotransferase is distinct from other hepatic sulfotransferases.     

Steroid sulfotransferase in hamster epididymis

Steroid sulfotransferase activity is present in the cytosol fraction of hamster epididymis. The activity of this enzyme is increased by magnesium ion. Cysteine is essential to assure optimal activity. Adenosine-3′-phosphate-5′-phosphosulfate is required as sulfate donor and an apparent K_m of 62 μM was calculated. Inhibition studies suggest that this enzyme preferentially catalyzes the sulfurylation of the 3β-hydroxyl group of Δ⁵-steroids. An unusual feature of the enzyme is a pH optimum at pH 10.     

Partial purification and characterization of 3'-phosphoadenylylsulfate:keratan sulfate sulfotransferases

Two 3'-phosphoadenylylsulfate:keratan sulfate sulfotransferases were purified 600-fold and 340-fold, respectively, from isolated bovine cornea cells. Sulfotransferase I exhibited an apparent Mr = 220,000, whereas an Mr = 140,000 was calculated for sulfotransferase II. The final preparations were both devoid of chondroitin sulfate sulfotransferase activity. The position of sulfation was determined by proton nuclear magnetic resonance spectroscopy. Sixty per cent of the sulfate ester groups formed by sulfotransferase I were linked to the C-6 atom of galactosyl residues, the other ones to the C-6 atom of N-acetylglucosamine. Sulfotransferase II showed a different specificity: 23% of the newly formed sulfate ester groups were on galactosyl and 77% on N-acetylglucosaminyl residues. Both sulfotransferase preparations acted in a cooperative manner. In the presence of both sulfotransferases, the incorporation of [35S]sulfate into keratan sulfate was up to 75% higher than could be expected from the sum of individual activities. From the specific radioactivities of the oligosaccharides produced by digestion with endo-beta-galactosidase, it was also concluded that both enzyme species reacted best with keratan sulfate segments exhibiting a relatively high degree of sulfation.     

Subcellular and developmental studies of the tyrosyl protein sulfotransferase in rat brain

• 1.1. Tyrosyl protein sulfotransferase (TPS) activity in the newborn and mature rat brain was studied using the cholecystokinin derivative terbutyloxycarbonyl-Asp-Tyr-Met-Gly-Trp-Met-Asp-PheNH₂, BocCCK-8(ns), as the peptide substrate.
• 2.2. TPS activity was enriched 4 times in the microsomal and synaptic vesicular enriched fractions of rat cerebral cortex.
• 3.3. CCK-8 content, in the subcellular fractions and the peptide sulfation activity distribution was in accord with the hypothesis that tyrosyl protein sulfotransferase plays a key role in the maturation process of bioactive CCK.
• 4.4. TPS activity measured in membranes from newborn brain was 2.5 times higher than the activity observed in the mature brain membranes with a V_max = 0.83 ± 0.05 and 0.31 ± 0.02 respectively. The apparent K_M for the sulfate donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), was similar, 94 ± 4 nM and 90 ± 6 nM and the k_M for the peptide substrate, BocCCK-8(ns), was 234 ± 16 μM and 160 ± 12 μM in the newborn and adult brain membranes respectively.
• 5.5. TPS activity reached normal mature values within 20 days of age.
• 6.6. These data support the idea that tyrosyl protein sulfation is an important process in the secretion mechanism and in the CCK maturation.

     

Enzymatic sulfation of a large molecular weight glycoprotein associated with pig brain membranes

Pig brain membranes catalyze the transfer of [³⁵S]sulfate from 3′-phosphoadenosine 5′-phospho[³⁵S]sulfate into two macromolecular endogenous acceptors. Several operational enzymatic properties of the sulfotransferase activity have been defined. An apparent K_m = 0.65 μm for 3′-phosphoadenosine 5′-phosphosulfate has been determined for the pig brain in vitro sulfotransferase system. Direct proof for the absolute requirement of the 3′-phosphate moiety of 3′-phosphoadenosine 5′-phosphosulfate is presented. The nucleotide end product, 3′,5′-ADP, is a potent competitive inhibitor of the pig brain sulfotransferase activity. One of the major products enzymatically labeled during incubation with 3′-phosphoadenosine 5′-phospho[³⁵S]sulfate is a membrane-bound glycoprotein of high molecular weight. The sulfated glycoprotein appears to be an integral membrane glycoprotein, requiring 1% Triton X-100 for extraction. An ³⁵S-labeled oligosaccharide, released by mild base treatment, contains O-sulfate ester groups and at least one N-acetylneuraminic acid residue. The sulfated glycoprotein has an apparent molecular weight of 198,000. Under the same in vitro conditions [³⁵S]sulfate is also incorporated into a membrane-associated ³⁵S-labeled proteoglycan having the properties of heparan sulfate. The ³⁵S-labeled proteoglycan is electrostatically bound to the pig brain membranes, and can be readily extracted with 1 m NaCl.     

The effect of chronic ethanol consumption on temperature-dependent physical properties of liver mitochondrial membranes

We have reported that the monovalent ionophore monensin causes undersulfated chondroitin sulfate biosynthesis in cultured chondrocytes. In order to clarify the mechanism of this diminished sulfation, we have measured the rate of incorporation of sulfate into chondrocytes and assayed the cellular ATP levels. We have also measured sulfatase activity, the incorporation of ³⁵SO₄ into 3′-phosphoadenosine 5′-phospho[³⁵S]sulfate and endogenous sulfotransferase activity in the cell-free extracts. We find that: (1) The incorporation of ³⁵SO₄ into the free sulfate pool in chondrocytes was not inhibited by monensin. (2) The ATP levels of monensin-treated chondrocytes were the same as control cells. (3) There was no sulfatase activity in both control and monensin-treated chondrocytes. (4) Enzymatic analyses revealed that ³⁵SO₄ incorporation into 3′-phosphoadenosine 5′-phospho[³⁵S]sulfate and subsequent sulfotransferase activity were not inhibited in the presence of monensin. At present the most tenable hypothesis to account for monensin causing undersulfated chondroitin sulfate synthesis is that the ionophore impairs the access of proteoglycans to the sulfotransferases in the luminal walls of the Golgi structures.     

Enzymatic sulfation of steroids. II. The sulfation of corticosterone by the glucocorticoid sulfotransferases of rat liver cytosol

A radioisotopic assay for the cytoplasmic corticosterone sulfotransferase activity of rat liver was developed. The steroid inhibits the enzyme reaction. For reliable results, a complex assay method, using three different corticosterone concentrations, each studied with several different amounts of enzyme, was necessary. This "mosaic" assay compensates for observed biological, gonadal and seasonal enzyme fluctuations. Cytosols from female rats contain 6--9-times the enzyme activity found in males. The sulfation product with both sexes is corticosterone-21-sulfate. The effects of castration and of androgen administration on hepatic cortisol and corticosterone sulfation were compared in female rats. Ovariectomy resulted in 20--32% and 25--35% decreases of hepatic corticosterone and cortisol sulfotransferase activity, respectively. Androgen administration caused 37--55% and 40--60% decreases of sulfation of the two steroids. The data suggest the equivalence of hepatic cortisol and corticosterone sulfotransferases. Fractionation of cytosols from female rats, on DEAE-Sephadex A-50 columns, resolved three peaks of corticosterone sulfotransferase activity which eluted concurrently with the hepatic cortisol sulfotransferases I, II and III. They appear to be the same enzymes. Cytosol from males contained cortisosterone sulfotransferase activity due mostly to sulfotransferase III. Sulfotransferases I and II appear to have higher turnover numbers for hepatic cortisol than for corticosterone. The reverse is true for sulfotransferase III.     

An in vitro assay of 20-hydroxyecdysone sulfotrasferase in the mosquito,Aedes togoi

Sulfate conjugation of 20-hydroxyecdysone and related ecdysteroids was studies by a radiometric assay. The formation of 20-hydroxyecdysone ³⁵sulfate from PAP³⁵S (3′phosphoadenosine 5′phosphosulfate) proceeded linearly for 15 min at a pH optimum of 8.4. The apparent K_m values for PAP³⁵S and 20-hydroxyecdysone were 1.29 and 24.6 μM, respectively. The overall sulfate conjugation of 20-hydroxyecdysone was also demonstrated with ATP, Mg²⁺ and sodium ³⁵sulfate. The sulfotransferase activity showed a peak at puparium formation and a progressive increase after adult eclosion. The specific activity of the newly emerged female pupae was higher than that of the males. The reverse pattern was however observed in the adult mosquitoes where the activity of the male adult was about 2 times higher. The likely sites on the ecdysteroid molecule for sulfate conjugation are discussed.     

Aryl sulfotransferase IV from rat liver

A group of aryl sulfotransferases has been identified that catalyzes sulfate ester formation with simple phenols at an acidic pH and with several physiological metabolites at a more alkaline pH. One enzyme, aryl sulfotransferase IV, has been purified to homogeneity and found to be a protein of 61,000 daltons composed of two subunits of apparent equal size. Homogeneous preparations are active with simple phenols, organic hydroxylamines, and catecholamines as well as serotonin and its metabolites. The enzyme is also active with tyrosine methyl ester and with those peptide hormones e.g., cholecystokinin heptapeptide and some of the enkephalins, which have N-terminal tyrosine residues.     

Regulation of adenosine 5'-phosphosulfate sulfotransferase by sulfur dioxide in primary leaves of beans (Phaseolus vulgaris)

SO₂ inhibited the light-induced increase of extractable adenosine 5′-phosphosulfate sulfotransferase in greening primary leaves of bean seedlings (Phaseolus vulgaris L. cv. Saxa (Radio) Stamm Vatter). In green primary leaves containing appreciable extractable adenosine 5′-phosphosulfate sulfotransferase activity, SO₂ treatment for 20 h decreased the activity of the enzyme to between 10 and 20% of the initial level. After removal of SO₂ from the air, the extractable adenosine 5′-phosphosulfate sulfotransferase activity increased after a lag, both in green and greening primary leaves, and was back to the control level after about 48 h. The sulfate concentration was increased about fourfold during SO₂ treatment. An increase in sulfate sulfur accompanied by a decrease in adenosine 5′-phosphosulfate sulfotransferase was also observed when bean seedlings, after excision of the roots, were transferred to nutrient solutions containing high sulfate concentrations, suggesting that sulfate is involved in the regulation of the enzyme.     

Crystal structure-based studies of cytosolic sulfotransferase

Sulfation is a widely observed biological reaction conserved from bacterium to human that plays a key role in various biological processes such as growth, development, and defense against adversities. Deficiencies due to the lack of the ubiquitous sulfate donor 3'-phosphoadenosine-5'-phosphosulfate (PAPS) are lethal in humans. A large group of enzymes called sulfotransferases catalyze the transfer reaction of sulfuryl group of PAPS to the acceptor group of numerous biochemical and xenochemical substrates. Four X-ray crystal structures of sulfotransferases have now been determined: cytosolic estrogen, hydroxysteroid, aryl sulfotransferases, and a sulfotransferase domain of the Golgi-membrane heparan sulfate N-deacetylase/N-sulfotransferase 1. These have revealed the conserved core structure of the PAPS binding site, a common reaction mechanism, and some information concerning the substrate specificity. These crystal structures introduce a new era of the study of the sulfotransferases.     

Xanthurenic acid is an endogenous substrate for the silkworm cytosolic sulfotransferase, bmST1

Sulfotransferase enzymes are known to regulate physiologically active substances such as steroids and catecholamines in mammals. Although invertebrates also express sulfotransferases, their biological function is mostly unclear. In a previous study, we reported that 4-nitrocatechol and the gallete ester are substrates for the silkworm sulfotransferase bmST1. The K(m) of bmST1 for these substrates is high. However, endogenous substrates of bmST1 have not yet been determined. We therefore investigated endogenous bmST1 substrates and carried out a detailed expression profile analysis of bmST1. We found that xanthurenic acid, a tryptophan metabolite, is a possible endogenous substrate of bmST1. The K(m) of bmST1 for xanthurenic acid is low, in the μM range, which is lower than that for previously reported substrates. Additionally, xanthurenic acid is a tryptophan metabolite that characteristically shows toxicity in vivo. High dose administration of xanthurenic acid resulted in inhibition of cuticular biosynthesis. The expression of the bmST1 gene reached a maximal level in the Malpighian tubule at the 4th molting stage, when amino acid metabolism might be activated. Our results suggest that bmST1 plays a role in detoxification of xanthurenic acid in the silkworm.     

Adenosine 5‘-Phosphosulfate Sulfotransferase from Norway Spruce: Biochemical and Physiological Properties*

Biochemical and physiological properties of adenosine 5′-phosphosulfate sulfotransferase, a key enzyme of assimilatory sulfate reduction, from spruce trees growing under field conditions were studied. The apparent K_m for adenosine 5′-phosphosulfate (APS) was 29 ± 5.5μM, its apparent M_r was 115,000. 5′-AMP inhibited the enzyme competitively with a K_i of 1 mM, but also stabilized it. MgS0₄ at 800 mM increased adenosine 5′-phosphosulfate sulfotransferase activity by a factor of 3, concentrations higher than lOOOmM were inhibitory. Treatment of isolated shoots with nutrient solution containing 1 or 2 mM sulfate, and 3 or 10 mM glutathione, respectively, induced a significant decrease in extractable adenosine 5′-phosphosulfate sulfotransferase activity over 24h, whereas GSH as well as S^2- up to 5mM cysteine and up to 200 mM SO₃^2- had no effect on the in vitro activity of the enzyme. As with other enzymes involved in assimilatory sulfate reduction, namely ATP sulfurylase (EC 2.7.7.4), sulfite reductase (EC 1.8.7.1) and O-acetyl-L.-serine sulfhydrylase (EC 4.2.99.8), adenosine 5′-phosphosulfate sulfotransferase was still detected at appreciable activities in 2- and 3-year-old needles. Adenosine 5′-phosphosulfate sulfotransferase activity was low in buds and increased during shoot development, parallel to the chlorophyll content. The enzyme activity was characterized by an annual cycle of seasonal changes with an increase during February and March.     

Spondyloepiphyseal dysplasia, chondroitin sulfate type: a possible defect of PAPS--chondroitin sulfate sulfotransferase in humans

Four patients with an unusual form of spondyloepiphyseal dysplasia excreted in the urine undersulfated chondroitin 6-sulfate (Biochem. Med. $\text{7}$, 415–423, 1973). The sera of these patients show a low activity of PAPS — chondroitin sulfate sulfotransferase, while the undersulfated chondroitin sulfate present in their urine is a much better acceptor of ${}^{35}\text{SO}{}_4$ than standard chondroitin sulfate when they are incubated with [${}^{35}\text{S}$]PAPS and normal sulfotransferases. These results suggest that in these patients the skeletal lesions are secondary to a defect in the synthesis of chondroitin sulfate involving specifically the sulfotransferase activity.     

Determining heparan sulfate structure in the vicinity of specific sulfotransferase recognition sites by mass spectrometry

Sulfated motifs on heparan sulfate (HS) are involved in various extracellular processes from cell signaling to enzymatic regulation, but the structures of these motifs are obscure. We have developed a strategy to determine the structure of sulfotransferase recognition sites which constitute these motifs. Stable isotope is first introduced into specific sites on HS with HS sulfotransferases and the modified HS is then digested into oligosaccharides of differing sizes. The overlapping oligosaccharides containing the introduced stable isotope are identified by changes in the m/z profiles by mass spectrometry, and their relationships are elucidated. In this way, the HS structures in the vicinity of the sulfotransferase recognition site are quickly determined and groups on precursor structures of HS that direct the action of HS sulfotransferases are pinpointed.     

Enzymatic preparation of silybin phase II metabolites: sulfation using aryl sulfotransferase from rat liver

Aryl sulfotransferase IV (AstIV) from rat liver was overexpressed in Escherichia coli and purified to homogeneity. Using the produced mammalian liver enzyme, sulfation—the Phase II conjugation reaction—of optically pure silybin diastereoisomers (silybin A and B) was tested. As a result, silybin B was sulfated yielding 20-O-silybin B sulfate, whereas silybin A was completely resistant to the sulfation reaction. Milligram-scale sulfation of silybin B was optimized employing resting E. coli cells producing AstIV, thus avoiding the use of expensive 3′-phosphoadenosine-5′-phosphate cofactor and laborious enzyme purification. Using this approach, we were able to reach 48 % conversion of silybin B into its 20-sulfate within 24 h. The sulfated product was isolated by solid phase extraction and its structure was characterized by HRMS and NMR. Sulfation reaction of silybin appeared strictly stereoselective; only silybin B was sulfated by AstIV.     

Enzymatic sulfation of steroids III. The sulfation of corticosterone by the glucocorticoid sulfotranferases of rat liver cytosol

A radioisotopic assay for the cytoplasmic corticosterone sulfotransferase activity of rat liver was developed. The steroid inhibits the enzyme reaction. For reliable results, a complex assay method, using three different corticosterone concentrations, each studied with several different amounts of enzyme, was necessary. This ‘mosaic’ assay compensates for observed biological, gonadal and seasonal enzyme fluctuations. Cytosols from female rats contain 6–9-times the enzyme activity found in males. The sulfation product with both sexes is corticosterone-21-sulfate.The effects of castration and of androgen administration on hepatic cortisol and corticosterone sulfation were compared in female rats. Ovariectomy resulted in 20–32% and 25–35% decreases of hepatic corticosterone and cortisol sulfotransferase activity, respectively. Androgen administration caused 37–55% and 40–60% decreases of sulfation of the twoo steroids. The data suggest the equivalence of hepatic cortisol and corticosterone sulfotransferases.Fractionation of cytosols from female rats, on DEAE-Sephadex A-50 columns, resolved three peaks of corticosterone sulfotransferase activity which eluted concurrently with the hepatic cortisol sulfotransferase I, II and III. They appear to be the same enzymes. Cytosol from males contained cortisosterone sulfotransferase activity due to mostly to sulfotransferase III. Sulfotransferases I and II appear to have higher turnover numbers for hepatic cortisol than for corticosterone. The reverse is true for sulfotransferase III.     

Continuous fluorometric assay of phenol sulfotransferase.

Phenol sulfotransferases (EC 2.8.2.1) catalyze the sulfation of the acceptor hydroxyl group using 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as the donor substrate. Previous assays of these enzymes, which exhibit varied acceptor substrate specificities, have required termination of the catalysis followed by isolation and quantitation of formed sulfate ester. In this report, the sulfation of the fluorescent compound, resorufin, is investigated. Reaction of PAPS with resorufin, catalyzed by bovine lung phenol sulfotransferase, bleaches the emission of this acceptor at the pH of the reaction (pH 6.4 optimum). It is thereby possible to continuously record the sulfation reaction. Analysis of single progress curves by integrated replot can be used to determine the initial velocities and also indicates the formation of a product inhibitor, probably resorufin sulfate ester, with Ki less than Km. Sensitivity of the reaction is less than 1 pmol/min. The maximal rate of resorufin sulfation by the bovine lung enzyme is estimated at 57 nmol/mg/min, which is 10% of the rate with an optimal substrate 2-naphthol. This assay may be most sensitive for phenol sulfotransferases with optimal activities at greater than pH 6, due to the acid-base properties of resorufin (pK alpha 6), which becomes nonfluorescent upon protonation.     

Enzymatic assay for flavonoid sulfotransferase

A novel enzyme assay for flavonoid sulfotransferase is described. It makes use of tetrabutylammonium dihydrogen phosphate which forms a pair of ions with the flavonoid sulfate esters formed. This renders the sulfate ester soluble in organic solvents such as ethyl acetate, whereas the sulfate donor, 3'-phosphoadenosine-5'-phosphosulfate, remains in the aqueous reaction mixture. The procedure is simple, rapid, and reproducible. It eliminates the need for chromatographic separation of the reaction products, except when their identification is required, and is suitable for use in the purification and kinetic studies of sulfotransferases.     

Separation and characterization of chondroitin 6-sulfotransferase and chondroitin 4-sulfotransferase from chick embryo cartilage

Two distinct sulfotransferases (chondroitin 6-sulfotransferase and chondroitin 4-sulfotransferase), which catalyzed transfer of sulfate to position 6 and position 4 of acetylgalactosamine residues of chondroitin, were extracted from epiphyseal cartilage of 14-day-old chick embryos and separated by gel chromatography on Sephacryl S-200 in the presence of 3 M guanidine-HCl. When the enzyme solutions containing 3 M guanidine-HCl were dialyzed against 0.02 M Tris-HCl, pH 7.2, containing 10% glycerol, chondroitin 4-sulfotransferase became almost insoluble, whereas chondroitin 6-sulfotransferase remained soluble. Endogenous acceptors for sulfate transfer were completely removed from both enzyme preparations. Addition of basic proteins and polyamines as well as Mn²⁺ to the incubation medium caused a stimulation of both sulfotransferases; the stimulation of chondroitin 6-sulfotransferase with these cations was higher than that of chondroitin 4-sulfotransferase. The K_m values for 3′-phosphoadenylyl sulfate of both enzymes were much smaller in the presence of protamine or spermine than in the presence of Mn²⁺. The two sulfotransferases differed in the requirement for sulfhydryl compounds; in the absence of sulfhydryl compounds, the activity of chondroitin 4-sulfotransferase was very low, whereas the activity of chondroitin 6-sulfotransferase was essentially unaffected. These observations indicate that at least two sulfotransferases are involved in the biosynthesis of chondroitin sulfate, and suggest that the production of the isomers of chondroitin sulfate in chondrocytes is affected by various factors such as the intracellular concentration of sulfhydryl compounds and basic substances.