A promiscuous glutathione transferase transformed into a selective thiolester hydrolase
作者:Sofia Hederos、Lotta Tegler、Jonas Carlsson、Bengt Persson、Johan Viljanen、Kerstin S. Broo
DOI:10.1039/b510115h
日期:——
Human glutathione transferase A1-1 (hGST A1-1) can be reengineered by rational design into a catalyst for thiolester hydrolysis with a catalytic proficiency of 1.4 × 107 M−1. The thiolester hydrolase, A216H that was obtained by the introduction of a single histidine residue at position 216 catalyzed the hydrolysis of a substrate termed GSB, a thiolester of glutathione and benzoic acid. Here we investigate the substrate requirements of this designed enzyme by screening a thiolester library. We found that only two thiolesters out of 18 were substrates for A216H. The A216H-catalyzed hydrolysis of GS-2 (thiolester of glutathione and naphthalenecarboxylic acid) exhibits a kcat of 0.0032 min−1 and a KM of 41 µM. The previously reported catalysis of GSB has a kcat of 0.00078 min−1 and KM of 5 µM. The kcat for A216H-catalyzed hydrolysis of GS-2 is thus 4.1 times higher than for GSB. The catalytic proficiency (kcat/KM)/kuncat for GS-2 is 3 × 106 M−1. The promiscuous feature of the wt protein towards a range of different substrates has not been conserved in A216H but we have obtained a selective enzyme with high demands on the substrate.
人谷胱甘肽转移酶 A1-1 (hGSTA1-1) 可以通过合理设计重新设计成硫醇酯水解催化剂,催化效率为 1.4 × 107 M−1。通过在位置 216 引入单个组氨酸残基获得的硫醇酯水解酶 A216H 催化称为 GSB 的底物(谷胱甘肽和苯甲酸的硫醇酯)的水解。在这里,我们通过筛选硫醇酯库来研究这种设计的酶的底物要求。我们发现 18 种硫醇酯中只有两种是 A216H 的底物。 A216H 催化的 GS-2(谷胱甘肽和萘甲酸的硫醇酯)水解表现出 0.0032 min−1 的 kcat 和 41 µM 的 KM。之前报道的 GSB 催化作用的 kcat 为 0.00078 min−1,KM 为 5 µM。因此,A216H 催化的 GS-2 水解的 kcat 比 GSB 高 4.1 倍。 GS-2 的催化效率 (kcat/KM)/kuncat 为 3 × 106 M−1。 wt蛋白对一系列不同底物的混杂特征在A216H中并未得到保留,但我们获得了对底物有高要求的选择性酶。