Cha Sun-Shin, An Young Jun
Department of Chemistry & Nano Science, Ewha Womans University, Seoul, 03760, Republic of Korea.
Marine Biotechnology Research Center, Korea Institute of Ocean Science and Technology, Ansan 426-744, Republic of Korea.
Biochem Biophys Res Commun. 2016 Sep 16;478(2):818-24. doi: 10.1016/j.bbrc.2016.08.031. Epub 2016 Aug 5.
EstSRT1 is a family VIII carboxylesterase that hydrolyzes oxyimino third- and fourth-generation cephalosporins, first-generation cephalosporins and ester substrates. According to the crystal structure of EstSRT1 (2.0-Å resolution), this protein contains a large α/β domain and a small α-helical domain and harbors three catalytic residues (Ser71, Lys74, and Tyr160) in the cavity at the domain interface, similarly to other family VIII carboxylesterases. Comparison of the structures of EstSRT1 and EstU1, a family VIII carboxylesterase with no hydrolytic activity toward bulky oxyimino cephalosporins, revealed that EstSRT1 has a smaller active site, despite its extended substrate range. The B-factors of the active site segments that could potentially contact with the oxyimino groups and the R2 side chains of oxyimino cephalosporins are higher in EstSRT1 than in EstU1, thus suggesting the role of the active site's structural flexibility in the extension of EstSRT1's substrate spectrum.
EstSRT1是一种VIII族羧酸酯酶，可水解肟基第三代和第四代头孢菌素、第一代头孢菌素以及酯类底物。根据EstSRT1的晶体结构（分辨率为2.0 Å），该蛋白包含一个大的α/β结构域和一个小的α螺旋结构域，并且在结构域界面的腔内含有三个催化残基（Ser71、Lys74和Tyr160），这与其他VIII族羧酸酯酶类似。EstSRT1与EstU1（一种对大体积肟基头孢菌素无水解活性的VIII族羧酸酯酶）的结构比较表明，尽管EstSRT1的底物范围更广，但其活性位点较小。EstSRT1中可能与肟基头孢菌素的肟基和R2侧链潜在接触的活性位点片段的B因子高于EstU1，因此表明活性位点的结构灵活性在EstSRT1底物谱扩展中的作用。
