(442d) Characterization and Comparison of Alkyl Hydroperoxide Reductase and Water-Forming Nadh Oxidase

Authors: 
Jiang, R., Georgia Institute of Technology
Riebel, B. R., Emory University
Wellborn, W. B., Georgia Tech
Bommarius, A. S., Georgia Institute of Technology


NADH oxidases are useful biocatalysts for regenerating nicotinamide cofactors of many biological redox reactions. In this presentation, we compare the alkyl hydroperoxide reductase (AhpR) and the H2O-forming enzyme (nox-2) from Lactococcus lactis (L. lactis), as well as the H2O-former from Lactobacillus sanfranciscensis (L. sanfranciscensis). AhpR is composed of H2O2-forming NADH oxidase (nox-1) and peroxidase. The net reaction of AhpR is the same as nox-2. In this work, both nox-1 and nox-2 are found to be flavoproteins. We found a considerably lower maximum specific activity of nox-1 from L. lactis compared to its nox-2 counterpart or nox-2 from L. sanfranciscensis. Both nox-1 and nox-2 are turnover-limited, as expected for enzymes with labile, redox-active thiols in the active site. In the absence of exogenously added thiols, both nox-1 and nox-1/peroxidase are considerably more stable against overoxidation than nox-2. We will investigate the possibility of using the E. coli-based whole cell system for the oxidative biocatalysis reactions with carbonyl reductase and these flavoproteins.