Characterization of different enzymes catalyzing oxidative deamination of amines

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The crystal structure of a quinohemoprotein amine dehydrogenase from Pseudomonas putida has been determined at .1.9A resolution. The enzyme comprises three non-identical subunits ; a four-domain A-subunit that harbors adi-heme cytochrome c, a seven-bladed B-propeller B-subunit that provides part of the active site, and a small G-subunit that contains a novel cross-linked. proteinous quinone cofactor, cysteine tryptophylquinone. More suprisingly, the catalytic G-subunit contains three additional chemical cross-links that encage the cysteine trytpphylquinone cofactor, involving a cysteine side chain bridged to either an Asp or Glu residue all in a hitherto unknown thicether bonding with a methylene carbon atom of acidic amino acid side chains. Thus, the structure of the 79-residue G-subunit is quite unusual, containing four internal cross-links in such a short polypeptide chain that would otherwise be difficult to fold into a globular structure.Spermidine dehydrogenase from Citrobacter freundii and histamine dehydrogenase from Nocardioides simplex have also been crystallized for X-ray analysis, which may develop another new fields of quinoprotein chemistry. Furthermore, it is very much promising to have been succeeded in purification of cytokinin oxidase and amino-aldehyde dehydrogenase from plants sources.