A bireactant, irreversible, active-site-directed inhibitor of β-d-galactosidase (Escherichia coli). Synthesis and properties of (1/2,5,6)-2-(3-azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol
作者:Reuben E. Huber、Jochen Lehmann、Lothar Ziser
DOI:10.1016/s0008-6215(00)90528-7
日期:1991.8
(1/2,5,6)-2-(3-Azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol** (1) was synthesized and was found to irreversibly inactivate beta-D-galactosidase (Escherichia coli). The inactivation was prevented by the presence of isopropyl 1-thio-beta-D-galactopyranoside (IPTG). The vinyloxirane group of 1 reacted with water and other nucleophiles, especially at higher pH values. Reaction of 1 with beta-D-galactosidase was slow enough so that a competitive-inhibition constant (K(i)) of 29mM could be determined. The inhibition constant for (1,2/3,6)-6-3-azibutylthio)-2-bromo-4-cyclohexene-1,3-diol (2), the precursor of the bireactant inhibitor 1, was 13mM, while that of (1,3/2,4)-3-(3-azibutylthio)-5-cyclohexene-1,2,4-triol (3), the product formed when the reactant is allowed to react with water, was 23mM. After irradiation by light, beta-D-galactosidase that had initially been treated with the bireactant compound and then digested with trypsin, showed a new pattern of elution from h.p.l.c., indicating that there was reaction at two regions of the beta-D-galactosidase molecule.
(1/2,5,6)-2-(3-叠氮丁基硫基)-5,6-环氧-3-环己烯-1-醇 **(1)** 被合成,并且发现它可以不可逆地失活 β-D-半乳糖苷酶(大肠杆菌)。这种失活作用在有异丙基 1-硫代-β-D-半乳糖吡喃苷(IPTG)存在时会被抑制。化合物 1 的乙烯氧化物基团与水和其他亲核试剂反应,尤其是在较高 pH 值下。1 与 β-D-半乳糖苷酶的反应足够缓慢,因此可以测定其竞争性抑制常数(K(i))为 29 mM。对于 (1,2/3,6)-6-(3-叠氮丁基硫基)-2-溴-4-环己烯-1,3-二醇(2),即双反应抑制剂 1 的前体,其抑制常数为 13 mM;而对于 (1,3/2,4)-3-(3-叠氮丁基硫基)-5-环己烯-1,2,4-三醇(3),即反应物与水反应生成的产物,其抑制常数为 23 mM。当在光照下照射时,最初用双反应化合物处理然后用胰蛋白酶消化的 β-D-半乳糖苷酶显示出从高效液相色谱(HPLC)洗脱的新模式,这表明在 β-D-半乳糖苷酶分子的两个区域发生了反应。