Quinoproteins.
As used today, the word quinoprotein defines three distinct groups of enzymes. Before 1979, the structures of the essential, quinonoid oxidation-reduction cofactors were a mystery for all these enzymes. The first proteins proven to harbor this type prosthetic group are those with noncovalently bound pyrroloquinoline quinone (PQQ). PQQ-containing enzymes can be described as alcohol dehydrogenases, with the exception of a single protein, which is an amine dehydrogenase. More recently, it was discovered that copper-containing amine oxidases contain 6-hydroxydopa quinone, also known as topa quinone (TQ), whereas certain bacterial amine dehydrogenases require 2',4-bitryptophan-6,7-dione (tryptophan tryptophylquinone, TTQ) for activity. These latter two quinones are formed, by unknown processes, from a specific tyrosyl residue for the amine oxidases, and from two widely separate tryptophyl residues in the polypeptide of the amine dehydrogenases.
McIntire
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Molecular Biology Division, Department of Veterans Affairs Medical Center, San Francisco, California 94121.
D003067:Coenzymes / Q000502:physiology*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000502:physiology; D045563:Indolequinones; D010084:Oxidation-Reduction; D045542:PQQ Cofactor; D015363:Quinolones / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000502:physiology
D003067:Coenzymes; D045563:Indolequinones; D015363:Quinolones; D011809:Quinones; C070569:tryptophan tryptophylquinone; D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D045542:PQQ Cofactor; D014364:Tryptophan