Bioscience, Biotechnology, and Biochemistry
Online ISSN : 1347-6947
Print ISSN : 0916-8451
Analytical Chemistry Regular Paper
Thermodynamic Redox Properties Governing the Half-Reduction Characteristics of Histamine Dehydrogenase from Nocardioides simplex
Maiko TSUTSUMINobutaka FUJIEDASeiya TSUJIMURAOsamu SHIRAIKenji KANO
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JOURNAL FREE ACCESS

2008 Volume 72 Issue 3 Pages 786-796

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Abstract

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.

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© 2008 by Japan Society for Bioscience, Biotechnology, and Agrochemistry
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