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Quinone Cofactors

  1. Albert Lang,
  2. Judith P Klinman

Published Online: 15 FEB 2013

DOI: 10.1002/9780470015902.a0000660.pub2

eLS

eLS

How to Cite

Lang, A. and Klinman, J. P. 2013. Quinone Cofactors. eLS. .

Author Information

  1. University of California, California Institute of Quantitative Biosciences, Berkeley, California, USA

Publication History

  1. Published Online: 15 FEB 2013

Abstract

Quinone cofactors are used by several classes of enzymes, which catalyse the oxidation of biogenic amines and alcohols, to help catalyse these reactions. Before 1990 only one cofactor, the peptide-derived pyrroloquinoline quinone had been identified. During 1990–2001, however, four new quinone prosthetic groups derived from naturally occurring amino acids were discovered. The first protein-derived, nondissociable cofactor identified was 2,4,5-trihydroxyphenylalanine quinone, designated topaquinone (TPQ) in copper amine oxidases. The discovery of TPQ led to the identification of a series of new quinone cofactors, including lysine tyrosylquinone (LTQ) in lysyl oxidase, cysteine tryptophylquinone (CTQ) in quinohaemoprotein amine dehydrogenase and tryptophan tryptophylquinone (TTQ) in bacterial methylamine dehydrogenase. These cofactors contribute electrophillic capabilities (and stabilise free radical intermediates) that naturally occurring, unmodified amino acid side chains are unable to provide.

Key Concepts:

  • Quinone cofactors are a class of cofactors used by many enzymes to catalyse the oxidation of amines and alcohols.

  • Five quinone cofactors have been characterised: PQQ, TPQ, LTQ, TTQ and CTQ.

  • PQQ is a peptide-derived cofactor that involves the expression of six genes located within an operon.

  • TPQ is derived from a precursor tyrosine and requires only Cu2+ and O2 for biogenesis.

  • LTQ is formed by the cross-linking of a tyrosine residue and a lysine residue, also requiring only Cu2+ and O2.

  • TTQ is formed by the cross-linking of two tryprophan resides, with MauG completing biogenesis.

  • CTQ, the most recently discovered quinone cofactor, is formed by the cross-linking of a cysteine reside and a tryptophan residue.

Keywords:

  • structure and function;
  • catalytic mechanisms;
  • biogenesis;
  • model compounds