In biochemistry, sulfotransferases (SULTs) are transferase enzymes that catalyze the transfer of a sulfo group () from a donor molecule to an acceptor alcohol () or amine (). The most common sulfo group donor is 3'-phosphoadenosine-5'-phosphosulfate (PAPS). In the case of alcohol as acceptor, the product is a sulfate ():
whereas an amine leads to a sulfamate ():
Both reactive groups for a sulfonation via sulfotransferases may be part of a protein, lipid, carbohydrate, or steroid.
Examples The following are examples of sulfotransferases:
carbohydrate sulfotransferase: CHST1, CHST2, CHST3, CHST4, CHST5, CHST6, CHST7, CHST8, CHST9, CHST10, CHST11, CHST12, CHST13, CHST14 galactose-3-O-sulfotransferase: GAL3ST1, GAL3ST2, GAL3ST3, GAL3ST4 heparan sulfate 2-O-sulfotransferase: HS2ST1 heparan sulfate 3-O-sulfotransferase: HS3ST1, HS3ST2, HS3ST3A1, HS3ST3B1, HS3ST4, HS3ST5, HS3ST6 heparan sulfate 6-O-sulfotransferase: HS6ST1, HS6ST2, HS6ST3 N-deacetylase/N-sulfotransferase: NDST1, NDST2, NDST3, NDST4 tyrosylprotein sulfotransferase: TPST1, TPST2 uronyl-2-sulfotransferase Estrone sulfotransferase Chondroitin 4-sulfotransferase other: SULT1A1, SULT1A2, SULT1A3, SULT1A4, SULT1B1, SULT1C2, SULT1C3, SULT1C4, SULT1D1P, SULT1E1, SULT2A1, SULT2B1, SULT4A1, SULT6B1
Mechanism and structure The enzyme sulfotransferase catalyzes the sulfate transfer process with the use of 3'-phosphoadenosine-5'-phosphosulfate (PAPS), which is the form of the sulfate donor in its active state. Upon activation of the substrates for the catalysis, the substrate performs a nucleophilic attack on the sulfur atom from the sulfate group that has been transferred onto PAPS. This results in a transfer of the sulfate group and the creation of 3' phosphoadenosine-5-phosphate (PAP) as the products formed in the reaction. Kinetic and structural studies indicate that many sulfotransferases perform their catalysis via in-line nucleophilic substitution-like mechanism.
Many sulfotransferases possess conserved amino acid sequences or motifs, related to PAPS binding and catalytic activity. The central α/β fold of most cytosolic sulfotransferases contains a 5-stranded β-sheet running in a parallel fashion with surrounding α helix structures. Conserved residues within the active site help orient both the sulfate donor and the acceptor substrate, contributing to catalytic efficiency and substrate specificity.Rath VL, Verdugo D, Hemmerich S (2004). "Sulfotransferase structural biology and inhibitor discovery". Drug Discov. Today. 9 (23): 1003–1011.
Sulfotransferases are generally classified into cytosolic and membrane-associated forms. Cytosolic sulfotransferases participate primarily in the metabolism of hormones, neurotransmitters, xenobiotics, and drugs, whereas membrane-associated sulfotransferases localized in the Golgi apparatus are commonly involved in sulfation of carbohydrates, glycoproteins, and proteoglycans. Structural studies using X-ray crystallography have also provided insight into substrate recognition, conformational flexibility, and inhibitor binding among sulfotransferase families.
See also List of EC numbers (EC 2)#EC 2.8.2: Sulfotransferases List of MeSH codes (D08)#MeSH D08.811.913.817 – sulfur group transferases (EC_2.8)
References
External links