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.
CITATION STYLE
Tsutsumi, M., Fujieda, N., Tsujimura, S., Shirai, O., & Kano, K. (2008). Thermodynamic redox properties governing the half-reduction characteristics of histamine dehydrogenase from Nocardioides simplex. Bioscience, Biotechnology and Biochemistry, 72(3), 786–796. https://doi.org/10.1271/bbb.70665
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