title: Structure, function, and applications of tryptophan tryptophylquinone enzymes.
abstract: Tryptophan and tyrosine residues in proteins may be posttranslationally modified to form enzyme cofactors. Tryptophan tryptophylquinone (TTQ), the cofactor of methylamine dehydrogenase (MADH), is formed by covalent cross-linking of two tryptophan residues and incorporation of two oxygen atoms into one of the indole rings to form a quinone. MADH converts primary amines to their corresponding aldehydes plus ammonia. During the catalytic cycle, TTQ mediates electron transfer from substrate to a copper protein, amicyanin. These electrons are transferred to the respiratory chain via a c-type cytochrome. Structural, kinetic and site-directed mutagenesis studies have characterized protein-protein interactions, and mechanisms of catalysis and electron transfer by TTQ. Preliminary results obtained with MADH enzyme-electrodes demonstrate the potential for quinoprotein-based biosensors.
authors.affiliation: Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216, USA. vdavidson@biochem.umsmed.edu
authors.forename: V L
authors.initials: VL
authors.lastname: Davidson
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D015374:Biosensing Techniques; D004579:Electron Transport; D045563:Indolequinones; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000737:chemistry / Q000378:metabolism*; D010231:Paracoccus denitrificans / Q000201:enzymology; D011809:Quinones / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D045563:Indolequinones; D011809:Quinones; D011994:Recombinant Proteins; C017079:mauC protein, Methylobacterium extorquens; C070569:tryptophan tryptophylquinone; D014364:Tryptophan; C021567:methylamine dehydrogenase; D000587:Oxidoreductases Acting on CH-NH Group Donors; C037193:aromatic amine dehydrogenase