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Hyunjun Choe,이수미,황효진,주정찬,조대행,김용환 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.4
The efficient regeneration of nicotinamidecofactors is an important process for industrial applicationsbecause of their high cost and stoichiometric requirements. In this study, the FDH1 β-subunit of NAD-dependentformate dehydrogenase from Methylobacterium extorquensAM1 was heterologously expressed in Escherichia coli. Itshowed water-forming NADH oxidase (NOX-2) activity inthe absence of its α-subunit. The β-subunit oxidized NADHand generated NAD+. The enzyme showed a low NADHoxidation activity (0.28 U/mg enzyme). To accelerate electrontransfer from the enzyme to oxygen, four electron mediatorswere tested; flavin mononucleotide, flavin adenine dinucleotide,benzyl viologen (BV), and methyl viologen. Alltested electron mediators increased enzyme activity; additionof 250 μM BV resulted in the largest increase in enzymeactivity (9.98 U/mg enzyme; a 35.6-fold increase comparedwith that in the absence of an electron mediator). Withoutthe aid of an electron mediator, the enzyme had a substratebindingaffinity for NADH (Km) of 5.87 μM, a turnoverrate (kcat) of 0.24/sec, and a catalytic efficiency (kcat/Km) of41.31/mM/sec. The addition of 50 μM BV resulted in a22.75-fold higher turnover rate (kcat, 5.46/sec) and a 2.64-fold higher catalytic efficiency (kcat/Km, 107.75/mM/sec).
Communication—Highly Efficient Electroenzymatic NADH Regeneration by an Electron-Relay Flavoenzyme
Lee, Sumi,Choe, Hyunjun,Cho, Dae Haeng,Yoon, Sung Ho,Won, Keehoon,Kim, Yong Hwan The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.5
<P>Efficient cofactor regeneration is essential for the utilization of many oxidoreductases. Herein, the beta-subunit of formate dehydrogenase 1 from Methylobacterium extorquens AM1 (MeFDH1-beta) was employed as a novel electroactive biocatalyst for electroenzymatic NADH regeneration for the first time. MeFDH1-beta showed much better properties in both catalytic activity (a turnover frequency of 3,600 hr(-1)) and current efficiency (ca. 98%) than a conventional rhodium (III)-based chemical catalyst (M = [Cp*Rh(bpy)H2O](2+), Cp* = C5Me5, bpy = 2,2'-bipyridine) and a traditional biocatalyst (diaphorase). (C) 2016 The Electrochemical Society. All rights reserved.</P>