Luk Louis Y P, Loveridge E Joel, Allemann Rudolf K
School of Chemistry, Cardiff University , Main Building, Park Place, Cardiff CF10 3AT, United Kingdom.
J Am Chem Soc. 2014 May 14;136(19):6862-5. doi: 10.1021/ja502673h. Epub 2014 May 5.
The role of protein dynamics in the reaction catalyzed by dihydrofolate reductase from the hyperthermophile Thermotoga maritima (TmDHFR) has been examined by enzyme isotope substitution ((15)N, (13)C, (2)H). In contrast to all other enzyme reactions investigated previously, including DHFR from Escherichia coli (EcDHFR), for which isotopic substitution led to decreased reactivity, the rate constant for the hydride transfer step is not affected by isotopic substitution of TmDHFR. TmDHFR therefore appears to lack the coupling of protein motions to the reaction coordinate that have been identified for EcDHFR catalysis. Clearly, dynamical coupling is not a universal phenomenon that affects the efficiency of enzyme catalysis.
嗜热栖热袍菌二氢叶酸还原酶（TmDHFR）催化反应中蛋白质动力学的作用已通过酶同位素取代（¹⁵N、¹³C、²H）进行了研究。与之前研究的所有其他酶反应不同，包括大肠杆菌二氢叶酸还原酶（EcDHFR），其同位素取代导致反应性降低，而TmDHFR的氢化物转移步骤的速率常数不受同位素取代的影响。因此，TmDHFR似乎缺乏已在EcDHFR催化中确定的蛋白质运动与反应坐标的耦合。显然，动态耦合不是影响酶催化效率的普遍现象。
