N2O reduction and HD formation by nitrogenase from a nifV mutant of Klebsiella pneumoniae.
AUTOR(ES)
Liang, J
RESUMO
Dinitrogenase from a nifV mutant of Klebsiella pneumoniae contains an altered form of iron-molybdenum cofactor (FeMoco) that lacks a biologically active homocitric acid molecule. Change in the composition of FeMoco led to substantial variation in the kinetics of nitrogenase action. The KmS of the mutant enzyme for N2 and N2O were 0.244 and 0.175 atm (24,714 and 17,726 kPa), respectively. The km for N2 was higher and the Km for N2O was lower than that for the wild-type enzyme. The mutant enzyme was ineffective in N2 fixation, in N2O reduction, and in HD formation, as indicated by the low Vmax of these reactions with saturating levels of substrate and under conditions of saturating electron flux. These observations provide further support for the concept that N2, N2O, and D2 interact with the same form of dinitrogenase. H2 evolution by the mutant enzyme is only partially inhibited by CO. Observation that different numbers of electrons are stored in CO-inhibited than in noninhibited dinitrogenase before H2 is released suggests that the mutant enzyme has more sites responsible for H2 evolution than the wild-type enzyme, whose H2 evolution is not inhibited by CO.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=210033Documentos Relacionados
- Homocitrate cures the NifV- phenotype in Klebsiella pneumoniae.
- Nucleotide sequence of the nifE and nifN genes from Klebsiella pneumoniae.
- Roles of nifF and nifJ gene products in electron transport to nitrogenase in Klebsiella pneumoniae.
- Bacteriophage mu-induced deletions in a plasmid containing the nif (N2 fixation) genes of Klebsiella pneumoniae.
- N2O reduction by Vibrio succinogenes.
