Thermodynamic redox properties governing the half-reduction characteristics of histamine dehydrogenase from Nocardioides simplex.
Histamine dehydrogenase from Nocardioides simplex is a homodimer and belongs to the family of iron-sulfur flavoproteins having one [4Fe-4S] cluster and one 6-S-cysteinyl FMN per monomer. In the reductive titration with histamine, two-electron reduction occurred per monomer at pH<9, while single-electron reduction proceeded at pH>9. The substrate-reduced histamine dehydrogenase yielded an electron paramagnetic resonance spectral signal assigned to the flavin semiquinone. The signal intensity increased with pH up to pH 9 and reached a maximum at pH>9. These unique features are explained in terms of the redox potential of the cofactors, where the redox potential was evaluated over a pH range from 7 to 10 by using a spectroelectrochemical titration method for the flavin and cyclic voltammetry for the [4Fe-4S] cluster. The bell-type pH dependence of the enzymatic activity is also discussed in terms of the pH dependence of the centers' redox potential.
Tsutsumi
Maiko
M
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Fujieda
Nobutaka
N
Tsujimura
Seiya
S
Shirai
Osamu
O
Kano
Kenji
K
D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D005182:Flavin-Adenine Dinucleotide / Q000031:analogs & derivatives; D006632:Histamine; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins; D009618:Nocardiaceae / Q000201:enzymology*; D010084:Oxidation-Reduction; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry*; D013816:Thermodynamics
D007506:Iron-Sulfur Proteins; D005182:Flavin-Adenine Dinucleotide; C029276:flavin semiquinone; D006632:Histamine; D000587:Oxidoreductases Acting on CH-NH Group Donors; C506665:histamine dehydrogenase