Varin L, Ibrahim R K
Department of Biology, Concordia University, Montreal, Quebec, Canada.
J Biol Chem. 1992 Jan 25;267(3):1858-63.
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.
一种黄酮醇磺基转移酶（EC 2.8.2.-）已从绿黄菊（Flaveria chloraefolia）中纯化至表观均一，该酶催化硫酸基团从3'-磷酸腺苷5'-磷酸硫酸转移至黄酮醇苷元的3-羟基上。与匀浆相比，黄酮醇3-磺基转移酶的比活性提高了2000倍，回收率为9%。天然和变性酶的分子量均为34.5 kDa，表明该酶的活性形式为单体。该酶对黄酮醇苷元的3位表现出特异性，在pH 6.0和8.5时呈现两个活性峰值，不需要二价阳离子，且不受EDTA或巯基试剂的抑制。底物相互作用动力学和产物抑制的结果与有序双底物双产物机制一致，其中3'-磷酸腺苷5'-磷酸硫酸是第一个与酶结合的底物，3'-磷酸腺苷5'-磷酸是最后释放的产物。代表17个和33个氨基酸的两个肽段的氨基酸序列与已报道的动物磺基转移酶的氨基酸序列没有明显的序列相似性。针对绿黄菊3-磺基转移酶产生的抗体被发现与同一植物的3'-和4'-磺基转移酶活性发生交叉反应，表明这三种酶在结构上相关。
