Mechanism of Biogenesis and Catalytic Function of Peptidyl Built-in Quinone Cofactors

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Peptidyl built-in cofactors are produced by posttranslational modification of the cognate enzyme proteins, unlike ordinary cofactors which are mostly bio-synthesized from water soluble vitamins. In this study, we focused on two built-in quinone cofactor-containing enzymes, copper amine oxidase and quinohemoprotein amine dehydrogenase (QHNDH) that contain topa quinone (TPQ) and cysteine tryptophyl quinone (CTQ), respectively. For the reaction mechanism of copper amine oxidase, it has been demonstrated that the former reductive half-reaction is accompanied with the conformational change of TPQ. On the other hand, two proteins encoded close to the QHNDH genes, an [Fe-S]-cluster and S-adenosylmethionine-binding protein and a subtilisin-like protease, have been found to play essential roles for QHNDH biogenesis.