Probing the SpNOX substrate binding site for NADPH vs. NADH affinity

Abstract

NADPH oxidases (NOXes) are a family of eukaryotic enzymes that produce reactive oxygen species (ROS). These transmembrane enzymes move electrons from the substrate NADPH across the membrane to the final electron acceptor O2, forming the superoxide anion O2 −. SpNOX is a recently discovered prokaryotic NOX homolog that, unlike eukaryotic versions, is robust to bacterial expression and is active in detergent solution, making it a good model system for study of the NOX family. Eukaryotic NOXes use NADPH exclusively as a substrate, while SpNOX has similar affinity for either NADH and NADPH. Tyrosine 353 in SpNOX occupies the same position in space as a well‐conserved arginine residue in eukaryotic NOX; by homology to other NADPH binding sites this R should interact with both the adenine ring and the extra phosphate group of NADPH, explaining the eukaryotic NOX preference for NADPH. We have created Y353R and Y353A mutations in SpNOX to probe the effects of this position on the affinity of SpNOX for NADPH vs. NADH. These results will further define the NOX substrate binding site, crucial for drug discovery.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.