title: Engineering towards nitroreductase functionality in ene-reductase scaffolds.
abstract: Nitroreductases (NRs) and ene-reductases (ERs) both utilize flavin mononucleotide cofactors but catalyze distinct reactions. NRs reduce nitroaromatics, whereas ERs reduce unsaturated C=C double bonds, and these functionalities are known to somewhat overlap. Recent studies on the ER xenobiotic reductase A (XenA) from Pseudomonas putida demonstrated the possibility of increasing NR activity with active site modifications. Structural comparison between NRs and ERs led us to hypothesize that active site cavity size plays an important role in determining enzyme functionality. Residues of ER KYE1 from Kluyveromyces lactis were selected to increase the binding pocket size, compensate for hydrogen bonding pattern changes, and eliminate ER activity. Single variants were screened, and promising mutations were combined. Variant F296A/Y275A showed a 100-fold improvement in NR specific activity over wild-type, and variant H191A/F296A/Y375A exhibited complete conversion to a NR.
authors.affiliation: School of Chemical and Biomolecular Engineering, Parker H. Petit Institute for Bioengineering and Bioscience, 315 Ferst Drive, Atlanta, GA 30332-0363 (USA).
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Park
authors.forename: Lizzette M
authors.initials: LM
authors.lastname: Gómez Ramos
authors.forename: Andreas S
authors.initials: AS
authors.lastname: Bommarius
mesh_terms: D020134:Catalytic Domain; D006860:Hydrogen Bonding; D013294:Lactococcus lactis / Q000201:enzymology; D008958:Models, Molecular; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering; D016958:Pseudomonas putida / Q000201:enzymology; D015007:Yersinia / Q000201:enzymology
chemical_list: D010088:Oxidoreductases
keywords: biocatalysis; flavins; oxidoreductases; protein engineering; substrate specificity