Title of Paper:Biochemical characteristics of a nitroreductase with diverse substrate specificity from Streptomyces mirabilis DUT001

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Date of Publication:2019-01-01

Journal:BIOTECHNOLOGY AND APPLIED BIOCHEMISTRY

Included Journals:PubMed、EI、SCIE

Volume:66

Issue:1

Page Number:33-42

ISSN No.:0885-4513

Key Words:biotransformation; diverse substrate specificity; flavin mononucleotide reduction; nitro compounds,nitroreductase; Streptomyces

Abstract:A nitroreductase-encoded gene from an efficient nitro-reducing bacterium Streptomyces mirabilis DUT001, named snr, was cloned and heterogeneously expressed in Escherichia coli. The purified Streptomyces nitroreductase SNR was a homodimer with an apparent subunit molecular weight of 24 kDa and preferred NADH to NADPH as a cofactor. By enzyme incubation and isothermal calorimetry experiments, flavin mononucleotide (FMN) was found to be the preferred flavin cofactor; the binding process was exothermic and primarily enthalpy driven. The enzyme can reduce multiple nitro compounds and flavins, including antibacterial drug nitrofurazone, priority pollutants 2,4-dinitrotoluene and 2,4,6-trinitrotoluene, as well as key chemical intermediates 3-nitrophthalimide, 4-nitrophthalimide, and 4-nitro-1,8-naphthalic anhydride. Among the substrates tested, the highest activity of k(cat(app))/K-m(app) (0.234 mu M-1 Sec(-1)) was observed for the reduction of FMN. Multiple sequence alignment revealed that the high FMN reduction activity of SNR may be due to the absence of a helix, constituting the entrance to the substrate pocket in other nitroreductases. (C) 2018 International Union of Biochemistry and Molecular Biology, Inc.