title: Laboratory evolution of P450 BM-3 for mediated electron transfer.
abstract: Preparative synthesis with P450 monooxygenases is hampered in cell-free systems by the requirement for cofactors such as NAD(P)H as reduction equivalents. A validated medium-throughput screening system was designed for improving P450 monooxygenases by mediated electron transfer with zinc/cobalt(III)sepulchrate (Zn/Co(III)sep) as an alternative and cost-effective cofactor system. The monooxygenase P450 BM-3 F87A was used as a model system for developing the screening system in a 96-well format. A coefficient of variation of less than 10% was achieved under optimized screening conditions. The mediator evolution screen was validated by comparing the activity of P450 BM-3 to P450 BM-3 F87A and by screening a saturation mutagenesis library at amino acid position R47. For mediated electron transfer, two double mutants P450 BM-3(F87A R47F) and P450 BM-3 (F87A R47Y) were identified with a two-threefold increased catalytic efficiency (up to 32 microM(-1) min(-1) for P450 BM-3(F87A R47F) and 34 microM(-1) min(-1) for P450 BM-3 (F87A R47Y)) compared to P450 BM-3 F87A. The kinetic constants of the double mutants are, in contrast to those of P450 BM-3 F87A, dependent on Co(III)sep concentration in the presence of NADPH. kcat increases from 145 min(-1) (0.25 mM Co(III)sep) to 197 min(-1) (0.5 mM Co(III)sep), and Km decreases simultaneously from 7.0 microM to 3.7 microM, for P450 BM-3 (F87A R47F). For P450 BM-3 (F87A R47Y), kcat increases from 138 min(-1) (0.25 mM Co(III)sep) up to 187 min(-1) (0.5 mM Co(III)sep), and Km decreases from 8.2 microM to 4.2 microM. Due to lower Km values, the catalytic efficiencies were improved six times for P450 BM-3 (F87A R47F) and three times for P450 BM-3 (F87A R47Y), when comparing catalytic efficiencies of the mediated electron-transfer system to the natural reduction equivalent NADPH.
authors.affiliation: International University Bremen, Campus Ring 8, 28759 Bremen, Germany.
authors.forename: Jovana
authors.initials: J
authors.lastname: Nazor
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schwaneberg
mesh_terms: D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D003035:Cobalt / Q000737:chemistry; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics; D019020:Directed Molecular Evolution / Q000379:methods*; D004579:Electron Transport; D004867:Equipment Design; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000235:genetics; D009249:NADP / Q000737:chemistry; D009251:NADPH-Ferrihemoprotein Reductase; D012680:Sensitivity and Specificity; D015032:Zinc / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D003035:Cobalt; D009249:NADP; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases; D015032:Zinc