Chu Yuan, Williams Nicholas H, Hengge Alvan C
Department of Chemistry and Biochemistry, Utah State University , Logan, Utah 84322-0300, United States.
Centre for Chemical Biology, Department of Chemistry, University of Sheffield , Sheffield S3 7HF, U.K.
Biochemistry. 2017 Aug 1;56(30):3923-3933. doi: 10.1021/acs.biochem.7b00441. Epub 2017 Jul 21.
Catalytically promiscuous enzymes are an attractive frontier for biochemistry, because enzyme promiscuities not only plausibly explain enzyme evolution through the mechanism of gene duplication but also could provide an efficient route to changing the catalytic function of proteins by mimicking this evolutionary process. PP1γ is an effectively promiscuous phosphatase for the hydrolysis of both monoanionic and dianionic phosphate ester-based substrates. In addition to its native phosphate monoester substrate, PP1γ catalyzes the hydrolysis of aryl methylphosphonates, fluorophosphate esters, phosphorothioate esters, and phosphodiesters, with second-order rate accelerations that fall within the narrow range of 10-10. In contrast to the different transition states in the uncatalyzed hydrolysis reactions of these substrates, PP1γ catalyzes their hydrolysis through similar transition states. PP1γ does not catalyze the hydrolysis of a sulfate ester, which is unexpected. The PP1γ active site is tolerant of variations in the geometry of bound ligands, which permit the effective catalysis even of substrates whose steric requirements may result in perturbations to the positioning of the transferring group, both in the initial enzyme-substrate complex and in the transition state. The conservative mutation of arginine 221 to lysine results in a mutant that is a more effective catalyst toward monoanionic substrates. The surprising conversion of substrate preference lends support to the notion that mutations following gene duplication can result in an altered enzyme with different catalytic capabilities and preferences and may provide a pathway for the evolution of new enzymes.
具有催化多效性的酶是生物化学中一个引人关注的前沿领域，因为酶的多效性不仅可以通过基因复制机制合理地解释酶的进化，还可以通过模拟这一进化过程为改变蛋白质的催化功能提供一条有效途径。PP1γ是一种对单阴离子和双阴离子磷酸酯类底物水解均有效的多效性磷酸酶。除了其天然的磷酸单酯底物外，PP1γ还催化芳基甲基膦酸酯、氟磷酸酯、硫代磷酸酯和磷酸二酯的水解，二级速率加速在10-10的狭窄范围内。与这些底物在非催化水解反应中的不同过渡态相反，PP1γ通过相似的过渡态催化它们的水解。PP1γ不催化硫酸酯的水解，这是出乎意料的。PP1γ活性位点能够容忍结合配体几何形状的变化，这使得即使是那些空间需求可能会导致转移基团在初始酶-底物复合物和过渡态中定位受到扰动的底物，也能实现有效催化。精氨酸221保守突变为赖氨酸会产生一个对单阴离子底物更有效的催化突变体。底物偏好的惊人转变支持了这样一种观点，即基因复制后的突变可以导致具有不同催化能力和偏好的酶发生改变，并可能为新酶的进化提供一条途径。
