Catalytic Proficiency: The Extreme Case of S–O Cleaving Sulfatases
作者:David R. Edwards、Danielle C. Lohman、Richard Wolfenden
DOI:10.1021/ja208827q
日期:2012.1.11
the spontaneous hydrolyses of aryl sulfate monoesters, which proceed by S-O cleavage. Extrapolation of a Bronsted plot [log(k(25)(N)) = (-1.81 ± 0.09) pK(a)(LG) + (3.6 ± 0.7)] based on the rate constants at 25 °C for hydrolysis of a series of sulfate monoesters to a pK(a)(LG) value of 16.1, typical of an aliphatic alcohol, yields k(25)(N) = 3 × 10(-26) s(-1). Comparison of that value with established
作为判断硫酸单酯酶催化能力的基准,我们试图确定未活化的烷基硫酸单酯通过 SO 键断裂的自发水解率。新戊基硫酸盐被证明不适合此目的,因为发现它通过 CO 键断裂机制进行水解,并重新排列其碳骨架。相反,我们检查了芳基硫酸酯单酯自发水解的温度依赖性,该水解通过 SO 裂解进行。基于 25 °C 水解 a 的速率常数,外推布朗斯台德图 [log(k(25)(N)) = (-1.81 ± 0.09) pK(a)(LG) + (3.6 ± 0.7)]一系列硫酸单酯的 pK(a)(LG) 值为 16.1,典型的脂肪醇,产量 k(25)(N) = 3 × 10(-26) s(-1)。将该值与细菌硫酸酯酶的既定 k(cat) 值进行比较表明,这些酶对硫酸酯单酯的水解产生高达 2 × 10(26) 倍的速率增强 (k(cat)/k(uncat))。这些速率增强超过了由磷酸水解酶(以前已知的最强大的生物催化剂)产生的