Structure of the phenylhydrazine adduct of the quinohemoprotein amine dehydrogenase from Paracoccus denitrificans at 1.7 A resolution.
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Datta S, Ikeda T, Kano K, Mathews FS
Structure of the phenylhydrazine adduct of the quinohemoprotein amine dehydrogenase from Paracoccus denitrificans at 1.7 A resolution.
Acta Crystallogr D Biol Crystallogr. 2003 Sep;59(Pt 9):1551-6. Epub 2003 Aug 19.
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- 12925784 [ View in PubMed]
- Abstract
The 109 kDa quinohemoprotein amine dehydrogenase (QHNDH) from Paracoccus denitrificans contains a novel redox cofactor, cysteine tryptophylquinone (CTQ). This cofactor is derived from a pair of gene-encoded amino acids by post-translational modification and was previously identified and characterized within an 82-residue subunit by chemical methods and crystallographic analysis at 2.05 A resolution. It contains an orthoquinone moiety bound to the indole ring and catalyzes the oxidation of aliphatic and aromatic amines through formation of a Schiff-base intermediate involving one of the quinone O atoms. This paper reports the structural analysis of the complex of QHNDH with the enzyme inhibitor phenylhydrazine determined at 1.70 A resolution. The phenylhydrazone product is attached to the C6 position, identifying the O6 atom of CTQ as the site of Schiff-base formation as postulated by analogy to another amine-oxidizing enzyme, methylamine dehydrogenase. Furthermore, the inner N atom closest to the phenyl ring of phenylhydrazine forms a hydrogen bond to gammaAsp33 in the complex, lending support to the hypothesis that this residue serves as the active-site base for proton abstraction during catalysis.