Uppenberg J, Ohrner N, Norin M, Hult K, Kleywegt G J, Patkar S, Waagen V, Anthonsen T, Jones T A
Department of Molecular Biology, Uppsala University, Sweden.
Biochemistry. 1995 Dec 26;34(51):16838-51. doi: 10.1021/bi00051a035.
Many lipases are potent catalysts of stereoselective reactions and are therefore of interest for use in chemical synthesis. The crystal structures of lipases show a large variation in the shapes of their active site environments that may explain the large variation in substrate specificity of these enzymes. We have determined the three-dimensional structure of Candida antarctica lipase B (CALB) cocrystallized with the detergent Tween 80. In another crystal form, the structure of the enzyme in complex with a covalently bound phosphonate inhibitor has been determined. In both structures, the active site is exposed to the external solvent. The potential lid-forming helix alpha 5 in CALB is well-ordered in the Tween 80 structure and disordered in the inhibitor complex. The tetrahedral intermediates of two chiral substrates have been modeled on the basis of available structural and biochemical information. The results of this study provide a structural explanation for the high stereoselectivity of CALB toward many secondary alcohols.
许多脂肪酶是立体选择性反应的高效催化剂，因此在化学合成中具有应用价值。脂肪酶的晶体结构显示其活性位点环境的形状存在很大差异，这可能解释了这些酶底物特异性的巨大差异。我们已经确定了南极假丝酵母脂肪酶B（CALB）与去污剂吐温80共结晶的三维结构。在另一种晶体形式中，已经确定了该酶与共价结合的膦酸酯抑制剂复合物的结构。在这两种结构中，活性位点都暴露于外部溶剂。CALB中潜在的形成盖子的α5螺旋在吐温80结构中排列有序，而在抑制剂复合物中则无序。基于现有的结构和生化信息，对两种手性底物的四面体中间体进行了建模。这项研究的结果为CALB对许多仲醇的高立体选择性提供了结构解释。
