ISOTHIOCYANATES AS SUBSTRATES FOR HUMAN GLUTATHIONE TRANSFERASES - STRUCTURE-ACTIVITY STUDIES
ISOTHIOCYANATES AS SUBSTRATES FOR HUMAN GLUTATHIONE TRANSFERASES - STRUCTURE-ACTIVITY STUDIES
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DOI：
10.1042/bj3110453
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发表时间：
1995-10-15
影响因子：
4.1
通讯作者：
MANNERVIK, B
中科院分区：
文献类型：
--
作者：
KOLM, RH;DANIELSON, UH;MANNERVIK, B
用14个异硫氰酸盐（R-NCS）底物检查了四种人谷胱甘肽转移酶（GSTS），A1-1，M1-1，M4-4和P1-1的催化特性。这些化合物包括脂肪族和芳香族同源物，其中一些是人类食物的天然组成部分，即硫二烷[1-异硫代糖酸 - 4--（甲基磺胺）丁烷]丁香蛋白[1-异硫氰酸酯[1-异硫代氨基氨基酸-4-4--（甲基硫酸盐]丁烷]，erysolin [1 butane] [1- -Isothiocyanato-4-（甲基磺酮）丁烷]，苄基-NC，苯乙基-NC和烯丙基-NC。所有研究的异硫氰酸盐都是四个GST的底物。这些酶促进异硫氰酸酯基的亲电中心碳的GSH添加，形成二硫代氨基烷[R-NH-C（= S）-SG]，在274 nm时具有较高的紫外线吸收。建立了所有化合物的摩尔吸收系数和非酶速率常数以及标准化的酶测定条件。在研究的四个同工酶中，GSTS M1-1和P1-1通常是最有效的催化剂，而GST M4-4的效率最低。异硫氰酸盐是最迅速共轭的GST底物之一。基于增强速率数据和结合能，将异硫氰酸盐与4-羟基烷烯烷进行比较，这是先前经过系统动力学分析的另一种天然GST底物。同源异硫氰酸盐中亚甲基数量增加的增量过渡状态稳定性与以前指出的同源4-羟基烷烃相似。
The catalytic properties of four human glutathione transferases (GSTs), A1-1, M1-1, M4-4 and P1-1, were examined with 14 isothiocyanate (R-NCS) substrates. The compounds include aliphatic and aromatic homologues, some of which are natural constituents of human food, namely sulphoraphane [1-isothiocyanato-4-(methylsulphinyl)butane], erucin [1-isothiocyanato-4-(methylthio)butane], erysolin [1-isothiocyanato-4-(methylsulphonyl)butane], benzyl-NCS, phenethyl-NCS and allyl-NCS. All isothiocyanates investigated were substrates for the four GSTs. The enzymes promote addition of the thiol group of GSH to the electrophilic central carbon of the isothiocyanate group to form dithiocarbamates [R-NH-C(=S)-SG] which have high UV absorption at 274 nm. Molar absorption coefficients and non-enzymic rate constants as well as standardized enzyme assay conditions for all compounds were established. Of the four isoenzymes investigated, GSTs M1-1 and P1-1 were generally the most efficient catalysts, whereas GST M4-4 was the least efficient. Isothiocyanates are among the GST substrates that are most rapidly conjugated. On the basis of rate-enhancement data and binding energies, the isothiocyanates were compared with 4-hydroxyalkenals, another class of natural GST substrates previously subjected to systematic kinetic analysis. The incremental transition-state stabilization attributable to an increased number of methylene groups in homologous alkyl isothiocyanates is similar to that previously noted for homologous 4-hydroxyalkenals.