title: A Hidden Transhydrogen Activity of a FMN-Bound Diaphorase under Anaerobic Conditions.
abstract: Redox cofactors of NADH/NADPH participate in many cellular metabolic pathways for facilitating the electron transfer from one molecule to another in redox reactions. Transhydrogenase plays an important role in linking catabolism and anabolism, regulating the ratio of NADH/NADPH in cells. The cytoplasmic transhydrogenases could be useful to engineer synthetic biochemical pathways for the production of high-value chemicals and biofuels.
  
  
  
  A transhydrogenase activity was discovered for a FMN-bound diaphorase (DI) from Geobacillus stearothermophilus under anaerobic conditions. The DI-catalyzed hydride exchange were monitored and characterized between a NAD(P)H and a thio-modified NAD+ analogue. This new function of DI was demonstrated to transfer a hydride from NADPH to NAD+ that was consumed by NAD-specific lactate dehydrogenase and malic dehydrogenase.
  
  
  
  We discover a novel transhydrogenase activity of a FMN-DI by stabilizing the reduced state of FMNH2 under anaerobic conditions. FMN-DI was demonstrated to catalyze the hydride transfer between NADPH and NAD+. In the future, it may be possible to incorporate this FMN-DI into synthetic enzymatic pathways for balancing NADH generation and NADPH consumption for anaerobic production of biofuels and biochemicals.
authors.affiliation: Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Collins
authors.affiliation: Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America.
authors.forename: Scott
authors.initials: S
authors.lastname: Huston
authors.affiliation: Cell Free Bioinnovations Inc., Blacksburg, Virginia 24060, United States of America.
authors.forename: Fangfang
authors.initials: F
authors.lastname: Sun
authors.affiliation: Cell Free Bioinnovations Inc., Blacksburg, Virginia 24060, United States of America.|Department of Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States of America.
authors.forename: Y-H Percival
authors.initials: YH
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America.|Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, New Jersey 08102, United States of America.
authors.forename: Jinglin
authors.initials: J
authors.lastname: Fu
mesh_terms: D001665:Binding Sites / Q000502:physiology; D002384:Catalysis; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D004579:Electron Transport / Q000502:physiology; D005486:Flavin Mononucleotide / Q000378:metabolism*; D001411:Geobacillus stearothermophilus / Q000378:metabolism; D006873:Hydroquinones / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000378:metabolism*; D009249:NADP / Q000378:metabolism; D009250:NADP Transhydrogenases / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D006873:Hydroquinones; C540087:flavin mononucleotide hydroquinone; D009243:NAD; D009249:NADP; D005486:Flavin Mononucleotide; D008291:Malate Dehydrogenase; D009250:NADP Transhydrogenases; D009245:NADH Dehydrogenase; D008058:Dihydrolipoamide Dehydrogenase