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Updated: Aug 14, 2026

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues
12:07

Sequence-specific Labeling of Nucleic Acids and Proteins with Methyltransferases and Cofactor Analogues

Published on: November 22, 2014

Cofactor-directed inactivation by nucleophilic amines of the quinoprotein methylamine dehydrogenase from Paracoccus

V L Davidson1, L H Jones

  • 1Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216-4505.

Biochimica Et Biophysica Acta
|May 22, 1992
PubMed

Insights

Phenylhydrazine and related compounds irreversibly inactivate methylamine dehydrogenase by modifying its tryptophan tryptophylquinone cofactor. These reactions provide insights into quinone cofactor interactions in enzymes.

Area of Science:

  • Biochemistry
  • Enzymology
  • Protein Chemistry

Background:

  • Methylamine dehydrogenase (MDH) is a key enzyme in methylotrophic metabolism.
  • The enzyme utilizes a unique tryptophan tryptophylquinone (TTQ) cofactor.
  • Understanding MDH inactivation mechanisms is crucial for enzyme function studies.

Purpose of the Study:

  • To investigate the inactivation of methylamine dehydrogenase by various hydrazine derivatives.
  • To elucidate the reaction mechanism between inactivators and the TTQ cofactor.
  • To compare these reactions with known quinone chemistries.

Main Methods:

  • Enzyme kinetics studies.
  • Spectroscopic analysis of TTQ cofactor.
  • Inactivation assays with phenylhydrazine, semicarbazide, aminoguanidine, hydrazine, and hydroxylamine.

Main Results:

  • All tested compounds irreversibly inactivated MDH.
  • Distinct spectral changes in the TTQ cofactor were observed for each inactivator.
  • Inactivation followed different kinetic patterns (bimolecular, saturation).
  • Ammonium salts acted as reversible competitive inhibitors.

Conclusions:

  • The TTQ cofactor is directly involved in the inactivation process.
  • The reaction mechanism varies depending on the inactivator.
  • These findings contribute to understanding quinone cofactor reactivity in enzymes.

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