6-sulfotransferase

Sulfotransferase catalyzes the transfer of sulfate from the donor molecule adenosine-3 -phosphate-5 -phosphosulfate (PAPS) to an acceptor, /3-naphthol, to form the reaction product /3-naphthol sulfate. 

The assay used for this activity involves the separation of the /3-naphthol from the product /3-naphthol sulfate by reversed-phase HPLC (Q8 column) with a mobile phase of 0.1 M acetic acid-acetonitrile (85 15 v/v). Absorbance was monitored at 235 nm. 

The reaction mixture contained the substrate /3-naphthol (0.125 M) in a phosphate buffer (pH 6.5), 5 mW 2-mercaptoethanol, and 0.2 mM PAPS in 5% acetone (v/v). The mixture was preincubated and the reaction started by the addition of a cytosolic fraction. The suspension was incubated for 10 minutes at 37°C, and the reaction was terminated by the addition of ice-cold methanol. After centrifugation to remove insoluble material, the supernatant solution was dried, redissolved in methanol, and analyzed by HPLC. 

3 Glutathione S-Transferaee (Brown et al., 1982 Eaton and Stapleton, 1989 Tracy and O Leary, 1991) 

Glutathione 5-transferases catalyze the reaction of electrophiles with glutathione to form thioether conjugates. Substrates include alkyl halides and organo-phosphorus insecticides. In the HPLC method of Brown et al. (1982), styrene oxide was used as the substrate and the activity was measured by the formation of conjugates between the styrene oxide and the reduced glutathione conjugates. 

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The metabolism of foreign compounds (xenobiotics) often takes place in two consecutive reactions, classically referred to as phases one and two. Phase I is a functionalization of the lipophilic compound that can be used to attach a conjugate in Phase II. The conjugated product is usually sufficiently water-soluble to be excretable into the urine. The most important biotransformations of Phase I are aromatic and aliphatic hydroxylations catalyzed by cytochromes P450. Other Phase I enzymes are for example epoxide hydrolases or carboxylesterases. Typical Phase II enzymes are UDP-glucuronosyltrans-ferases, sulfotransferases, N-acetyltransferases and methyltransferases e.g. thiopurin S-methyltransferase. 

Sulfotransferases catalyze the transfer of sulfate from PAPS to wide-range xenobiotics that possess hydroxyl groups. Steroid alcohols are among the endogenous substrates. The sulfotransferases exist in different forms. 

The microsomal fraction consists mainly of vesicles (microsomes) derived from the endoplasmic reticulum (smooth and rough). It contains cytochrome P450 and NADPH/cytochrome P450 reductase (collectively the microsomal monooxygenase system), carboxylesterases, A-esterases, epoxide hydrolases, glucuronyl transferases, and other enzymes that metabolize xenobiotics. The 105,000 g supernatant contains soluble enzymes such as glutathione-5-trans-ferases, sulfotransferases, and certain esterases. The 11,000 g supernatant contains all of the types of enzyme listed earlier. 

Dajani R, Cleasby A, Neu M, Wonacott AJ, Jhoti H, Hood AM, et al. X-ray crystal structure of human dopamine sulfotransferase, SULT1A3. J Biol Chem 1999 53 37862-8. 

Lee KA, Fuda H, Lee YC, Negishi M, Strott CA, Pedersen LC. Crystal structure of human cholesterol sulfotransferase (SULT2Blb) in the presence of pregnenolone and 3 -phosphoadenosine 5 -phosphate. Rationale for specificity differences between prototypical SULT2A1 and the SULT2BG1 isoforms. I Biol Chem 2003 278 44593-9. 

King RS, Sharma V, Pedersen LC, Kakuta Y, Negishi M, Duffel MW. Structure-function modeling of the interactions of the A-alkyl-A-hydroxyanilines with rat hepatic aryl sulfotransferase IV. Chem Res Toxicol 2000 13 1251-8. 

Bidwell LM, McManus ME, Gaedigk A, Kakuta Y, Negishi M, Pedersen L, et al. Crystal structure of human catecholamine sulfotransferase. / Mol Biol 1999 293 521-30. 

HARRIS R M, WARING R H, KIRK c J, HUGHES p J (2000) Sulfation of oestrogenic alkylphenols and 17beta-oestradiol by human platelet phenol sulfotransferases. J Biol Chem. 275 159-66. 

Tosylate derivatives are not usually found in nature, but sulfate derivatives of alcohols are common (52). They are formed by the reaction of an alcohol with sulfate, catalyzed by a sulfotransferase enzyme. 

Seibert C, Cadene M, Sanhz A, Chait BT, Sakmar TP. Tyrosine sulfation of CCR5 N-terminal peptide by tyrosylprotein sulfotransferases 1 and 2 follows a discrete pattern and temporal sequence. Proc Natl Acad Sci U S A 2002 99(17) 11031— 11036. 

Easterbrook, J., Liu, C., Sakai, Y. and Li, A.P. (2001) Effects of organic solvents on the activities of cytochrome P450 isoforms, UDP-dependent glucuronyl transferase, and phenol sulfotransferase in human hepatocytes. Drug Metabolism and Disposition The Biological Fate of Chemicals, 29, 141-144. 

The enterocyte expresses many of the metabolic enzymes that are expressed in the liver. These include UDP-glucuronyltransferases, sulfotransferases, esterases and cytochromes P450. 

Sulfotransferases are cytosolic enzymes that add sulfate to phenolic and hydroxyl functions as well as certain amines. The relative rates of sulfation of several sulfo-... 

From the above, it is clear that the gut wall represents more than just a physical barrier to oral drug absorption. In addition to the requirement to permeate the membrane of the enterocyte, the drug must avoid metabolism by the enzymes present in the gut wall cell as well as counter-absorptive efflux by transport proteins in the gut wall cell membrane. Metabolic enzymes expressed by the enterocyte include the cytochrome P450, glucuronyltransferases, sulfotransferases and esterases. The levels of expression of these enzymes in the small intestine can approach that of the liver. The most well-studied efflux transporter expressed by the enterocyte is P-gp. 

Quinone oxidoreductase, Sulfotransferase Drug metabolism 6 out of 22 coding region SNPs gave amino acid substitutions 15... 

Iida A, Sekine A, Saito S, Kitamura Y, Kitamoto T, Osawa S, Mishima C, Nakamura Y. Catalog of 320 single nucleotide polymorphisms (SNPs) in 20 qui-none oxidoreductase and sulfotransferase genes. J Hum Genet 2001 46 225-240. 

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