Publications

• Partial purification and characterization of three flavonol-specific sulfotransferases from Flaveria chloraefolia.

  Varin L., Ibrahim R.K.

  Three distinct flavonol-specific sulfotransferases were partially purified from the shoot tips of Flaveria chloraefolia A. Gray by fractional precipitation with ammonium sulfate, followed by gel filtration on Sephacryl S-200, 3'-phosphoadenosine 5-phosphate-Agarose affinity chromatography and chro ... >> More

  Three distinct flavonol-specific sulfotransferases were partially purified from the shoot tips of Flaveria chloraefolia A. Gray by fractional precipitation with ammonium sulfate, followed by gel filtration on Sephacryl S-200, 3'-phosphoadenosine 5-phosphate-Agarose affinity chromatography and chromatofocusing on Mono P. These enzymes exhibited expressed specificity for positions 3 of various flavonol acceptors and of 3' and 4' of flavonol 3-sulfate. The three sulfotransferases had similar molecular weights (35,000), exhibited no requirement for divalent cations and were not inhibited by SH group reagents. Their K(m) values for both the sulfate donor and the flavonol acceptors were of the same order of magnitude (ca. 0.2-0.4 micromolar). Except for the 3-sulfotransferase, which exhibited two optima at pH 6.5 and 8.5, the 3' and the 4'-sulfotransferases had a pH optimum of 7.5. The three enzymes could be resolved only by chromatofocusing and were eluted at pH 5.4, pH 6.0, and pH 5.1 for the 3-, 3'- and 4'-sulfotransferases, respectively. The substrate specificity of these three enzymes is discussed in relation to the biosynthesis of polysulfated flavonols in F. chloraefolia. << Less

  Plant Physiol. 90:977-981(1989) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Recent developments in the study of the structure-function relationship of flavonol sulfotransferases.

  Marsolais F., Varin L.

  With the rapid proliferation of sulfotransferase (ST) cDNA sequences in the last 5 years, consensus sequences were identified in four conserved regions. The association of these regions with substrate binding or catalysis was tested in several site-directed mutagenesis studies. Due to their strict ... >> More

  With the rapid proliferation of sulfotransferase (ST) cDNA sequences in the last 5 years, consensus sequences were identified in four conserved regions. The association of these regions with substrate binding or catalysis was tested in several site-directed mutagenesis studies. Due to their strict substrate and position specificities, the flavonol 3- and 4'-STs represent an advantageous model system for the study of the structure-function relationship of cytosolic STs. Using a combination of chimeric and site-directed mutant proteins, a domain was identified containing all the determinants responsible for the substrate specificity of these enzymes, and characterized amino acid residues conserved in all cloned STs that are involved in substrate binding and catalysis. This paper summarizes the results of these studies. << Less

  Chem Biol Interact 109:117-122(1998) [PubMed] [EuropePMC]

• Novel flavonol 3-sulfotransferase. Purification, kinetic properties, and partial amino acid sequence.

  Varin L., Ibrahim R.K.

  A flavonol sulfotransferase (EC 2.8.2.-), which catalyzes the transfer of the sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to the 3-hydroxyl group of flavonol aglycones, has been purified to apparent homogeneity from Flaveria chloraefolia. The specific activity of flavonol 3-sulfotrans ... >> More

  A flavonol sulfotransferase (EC 2.8.2.-), which catalyzes the transfer of the sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to the 3-hydroxyl group of flavonol aglycones, has been purified to apparent homogeneity from Flaveria chloraefolia. The specific activity of flavonol 3-sulfotransferase was enriched 2000-fold, as compared with the homogenate, with a recovery of 9%. The molecular mass of the native and denatured enzyme was found to be 34.5 kDa, suggesting that the active from of the enzyme is a monomer. The enzyme exhibited expressed specificity for position 3 of flavonol aglycones, showed two activity optima at pH 6.0 and 8.5, did not require divalent cations, and was not inhibited by either EDTA or sulfhydryl group reagents. The results of substrate interaction kinetics and product inhibition are consistent with an Ordered Bi Bi mechanism where 3'-phosphoadenosine 5'-phosphosulfate is the first substrate to bind to the enzyme and 3'-phosphoadenosine 5'-phosphate is the final product to be released. The amino acid sequence of two peptides representing 17 and 33 amino acids showed no significant sequence similarity with the amino acid sequences reported for animal sulfotransferases. Antibodies raised against F. chloraefolia 3-sulfotransferase were found to cross-react with the 3'- and 4'-sulfotransferase activities of the same plant, suggesting that the three enzymes are structurally related. << Less

  J. Biol. Chem. 267:1858-1863(1992) [PubMed] [EuropePMC]