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Quinoprotein-catalysed reactions
1Biochemistry Department, University of Southampton, U.K.
The Biochemical Journal
|December 15, 1996
Summary
Quinoprotein enzymes utilize quinone cofactors for catalysis. This review details their structures, mechanisms, and the roles of catalytic bases and redox centers in electron transfer.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Quinoproteins are enzymes with quinone cofactors, analogous to flavoproteins.
- Cofactors include pyrrolo-quinoline quinone (PQQ), tryptophan tryptophylquinone (TTQ), topaquinone (TPQ), and lysine tyrosylquinone (LTQ).
Purpose of the Study:
- To review the structure and function of quinoprotein enzymes.
- To correlate mechanisms with recently determined three-dimensional structures.
Main Methods:
- Literature review of quinoprotein enzymes.
- Analysis of structural data and proposed reaction mechanisms.
Main Results:
- Quinone cofactors are crucial for enzyme mechanisms.
- A catalytic base (aspartate) initiates reactions by proton abstraction.
- Enzyme mechanisms involve a reduced prosthetic group followed by an oxidative phase with electron transfer.
Conclusions:
- Quinone structure and catalytic bases are key features of quinoprotein function.
- Electron transfer mechanisms, particularly the oxidative phase, require further investigation.