Structural Principles of Covalent Flavin Modification in Oxidoreductases

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Flavin-dependent oxidoreductases utilize the versatile isoalloxazine cofactor for diverse biochemical reactions.
• The N5 and C4a atoms of flavin are crucial for catalysis and can undergo covalent modification.
• Covalent modification can lead to enzyme inactivation, impacting biological processes.

Purpose of the Study:

• To review structurally validated examples of covalent flavin inactivation in enzymes.
• To identify common structural outcomes and enzyme families susceptible to covalent modification.
• To explore the mechanistic basis and distribution of covalent flavin inactivation.

Main Methods:

• Analysis of X-ray crystallography data from the Protein Data Bank.
• Review of literature on flavoenzyme inactivation mechanisms.
• Integration of structural, mechanistic, and inhibitor design perspectives.

Main Results:

• Covalent flavin modification occurs in multiple enzyme families, including monoamine oxidases and dehydrogenases.
• Common outcomes include N5 or C4a alkylation, flavin reduction, and ring distortion.
• Amine oxidases and dehydrogenases are frequently inactivated due to iminium intermediate formation during C-N bond oxidation.

Conclusions:

• The structural record reveals recurring patterns in covalent flavin inactivation.
• Mechanistic features of certain enzyme classes predispose them to irreversible flavin modification.
• Understanding these mechanisms informs enzyme function studies and inhibitor design.