title: Role of surface residue 184 in the catalytic activity of NADH oxidase from Streptococcus pyogenes.
abstract: Nicotinamide adenine dinucleotide (NADH) oxidase from Streptococcus pyogenes (SpNox) is a flavoprotein harboring one molecule of noncovalently bound flavin adenine dinucleotide. It catalyzes the oxidation of NADH by reducing molecular O2 to H2O directly through a four-electron reduction. In this study, we selected the lysine residues on the surface of SpNox and mutated them into arginine residues to study the effect on the enzyme activity. A single-point mutation (K184R) at the surface of SpNox enhanced NADH oxidase activity by approximately 50 % and improved thermostability with 46.6 % longer half life at 30 °C. Further insights into the function of residue K184 were obtained by substituting it with other nonpolar, polar, positively charged, and negatively charged residues. To elucidate the role of this residue, computer-assisted molecular modeling and substrate docking were performed. The results demonstrate that even a single mutation at the surface of the enzyme induces changes in the interaction at the active site and affects the activity and stability. Additionally, the data also suggest that the K184R mutant can be used as an effective biocatalyst for NAD(+) regeneration in L-rare sugar production.
authors.affiliation: Department of Chemical Engineering, Konkuk University, 1 Hwayang-Dong, Gwangjin-Gu, Seoul, 143-701, South Korea.
authors.forename: Hui
authors.initials: H
authors.lastname: Gao
authors.forename: Manish Kumar
authors.initials: MK
authors.lastname: Tiwari
authors.forename: Raushan Kumar
authors.initials: RK
authors.lastname: Singh
authors.forename: Bong Hyun
authors.initials: BH
authors.lastname: Sung
authors.forename: Sun Chang
authors.initials: SC
authors.lastname: Kim
authors.forename: Jung-Kul
authors.initials: JK
authors.lastname: Lee
mesh_terms: D019943:Amino Acid Substitution; D004795:Enzyme Stability; D005420:Flavoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008239:Lysine / Q000235:genetics*; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D017354:Point Mutation; D013297:Streptococcus pyogenes / Q000201:enzymology* / Q000235:genetics; D013696:Temperature; D014867:Water / Q000378:metabolism
chemical_list: D005420:Flavoproteins; D009097:Multienzyme Complexes; D050505:Mutant Proteins; D014867:Water; D009243:NAD; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D008239:Lysine; D010100:Oxygen