Qiang Zhou1, Jian Gao2, Ye-Wang Zhang3. 1. School of Pharmacy, Jiangsu University, Zhenjiang, 212013, People's Republic of China. 2. College of Petroleum and Chemical Engineering, Qinzhou, 535100, People's Republic of China. 3. School of Pharmacy, Jiangsu University, Zhenjiang, 212013, People's Republic of China. zhangyewang@ujs.edu.cn.
Abstract
OBJECTIVE: To improve the activity of a water-forming NADH oxidase from Lactobacillus rhamnosus under neutral or alkaline pH for coupling NAD+-dependent dehydrogenases with an alkaline optimal pH. RESULTS: The water-forming NADH oxidase from Lactobacillus rhamnosus was engineered by replacing the aspartic acid or glutamic acid with arginine on the surface. The mutant D251R improved the activity with a 112%, 111%, and 244% relative activity to the wild-type at pH 6.5, pH 7.0, and pH 7.5, respectively. Docking substrate into the D251R mutant reveals that the NADH is access to the substrate-binding site with a larger substrate loop due to the enhanced electrostatic repulsion between ARG-251 and ARG-243. In the D251R-NADH complex, the carboxyl of NADH additionally forms two hydrogen bonds (2.6 and 2.9 Å) with G154 due to the changed interaction of substrate and the residues in the catalytic sites, and the hydrogen bond with the oxygen of carbonyl in P295 is shortened from 2.9 to 2.0 Å, which could account for the enhanced specific activity. CONCLUSIONS: The D251R mutant displayed higher catalytic activity than the wild-type in the pH range 6.5-7.5, and further insight into those shorter and newly formed hydrogen bonds in substrate docking analysis could account for the higher bind affinity and catalytic efficiency of D251R mutant.
OBJECTIVE: To improve the activity of a water-forming NADH oxidase from Lactobacillus rhamnosus under neutral or alkaline pH for coupling NAD+-dependent dehydrogenases with an alkaline optimal pH. RESULTS: The water-forming NADH oxidase from Lactobacillus rhamnosus was engineered by replacing the aspartic acid or glutamic acid with arginine on the surface. The mutant D251R improved the activity with a 112%, 111%, and 244% relative activity to the wild-type at pH 6.5, pH 7.0, and pH 7.5, respectively. Docking substrate into the D251R mutant reveals that the NADH is access to the substrate-binding site with a larger substrate loop due to the enhanced electrostatic repulsion between ARG-251 and ARG-243. In the D251R-NADH complex, the carboxyl of NADH additionally forms two hydrogen bonds (2.6 and 2.9 Å) with G154 due to the changed interaction of substrate and the residues in the catalytic sites, and the hydrogen bond with the oxygen of carbonyl in P295 is shortened from 2.9 to 2.0 Å, which could account for the enhanced specific activity. CONCLUSIONS: The D251R mutant displayed higher catalytic activity than the wild-type in the pH range 6.5-7.5, and further insight into those shorter and newly formed hydrogen bonds in substrate docking analysis could account for the higher bind affinity and catalytic efficiency of D251R mutant.
Authors: Garrett M Morris; Ruth Huey; William Lindstrom; Michel F Sanner; Richard K Belew; David S Goodsell; Arthur J Olson Journal: J Comput Chem Date: 2009-12 Impact factor: 3.376