Structure, function, and applications of tryptophan tryptophylquinone enzymes.
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.
Davidson
V L
VL
Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216, USA. vdavidson@biochem.umsmed.edu
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
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