title: Isotopic fractionation associated with [NiFe]- and [FeFe]-hydrogenases.
abstract: BACKGROUND
  Hydrogenases catalyze the reversible formation of H2 from electrons and protons with high efficiency. Understanding the relationships between H2 production, H2 uptake, and H2-H2O exchange can provide insight into the metabolism of microbial communities in which H2 is an essential component in energy cycling.
  
  
  METHODS
  We used stable H isotopes (1H and 2H) to probe the isotope effects associated with three [FeFe]-hydrogenases and three [NiFe]-hydrogenases.
  
  
  RESULTS
  All six hydrogenases displayed fractionation factors for H2 formation that were significantly less than 1, producing H2 that was severely depleted in 2H relative to the substrate, water. Consistent with differences in their active site structure, the fractionation factors for each class appear to cluster, with the three [NiFe]-hydrogenases (α = 0.27–0.40) generally having smaller values than the three [FeFe]-hydrogenases (α = 0.41–0.55). We also obtained isotopic fractionation factors associated with H2 uptake and H2-H2O exchange under conditions similar to those utilized for H2 production, providing a more complete picture of the reactions catalyzed by hydrogenases.
  
  
  CONCLUSIONS
  The fractionation factors determined in our studies can be used as signatures for different hydrogenases to probe their activity under different growth conditions and to ascertain which hydrogenases are most responsible for H2 production and/or uptake in complex microbial communities.
authors.forename: Hui
authors.initials: H
authors.lastname: Yang
authors.forename: Hasand
authors.initials: H
authors.lastname: Gandhi
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Cornish
authors.forename: James J
authors.initials: JJ
authors.lastname: Moran
authors.forename: Helen W
authors.initials: HW
authors.lastname: Kreuzer
authors.forename: Nathaniel E
authors.initials: NE
authors.lastname: Ostrom
authors.forename: Eric L
authors.initials: EL
authors.lastname: Hegg
mesh_terms: D005591:Chemical Fractionation; D016825:Chlamydomonas reinhardtii / Q000201:enzymology; D003013:Clostridium / Q000201:enzymology; D003903:Deuterium / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D020592:Shewanella / Q000201:enzymology
chemical_list: D007506:Iron-Sulfur Proteins; D006859:Hydrogen; D003903:Deuterium; C118830:iron hydrogenase; C043296:nickel-iron hydrogenase; D006864:Hydrogenase