Flavoenzymes inhibited by indomethacin.

Area of Science:

• Biochemistry
• Enzymology
• Pharmacology

Background:

• Flavoenzymes play crucial roles in various metabolic pathways.
• Indomethacin is a widely used non-steroidal anti-inflammatory drug (NSAID).
• Understanding drug-enzyme interactions is vital for drug development and safety.

Purpose of the Study:

• To investigate the inhibitory effects of indomethacin on a panel of flavoenzymes.
• To characterize the mechanism of inhibition for sensitive enzymes.
• To assess indomethacin's impact on other enzyme classes like dehydrogenases and hydrolases.

Main Methods:

• Enzyme activity assays were performed using purified enzymes and subcellular fractions.
• Inhibition kinetics were determined by varying substrate and inhibitor concentrations.
• Competitive inhibition was assessed by analyzing kinetic parameters (Ki values).

Main Results:

• Indomethacin inhibited D-amino acid oxidase, flavin-containing monooxygenases, cyclohexanone monooxygenase, NADPH-quinone reductase, and glutathione reductase.
• Inhibition was competitive with D-alanine for D-amino acid oxidase and with NADPH for other sensitive flavoenzymes.
• Indomethacin showed weaker inhibition of some dehydrogenases and esterases, with no effect on glucose oxidase or NADPH-cytochrome P-450 reductase.

Conclusions:

• Indomethacin exhibits broad inhibitory activity against various flavoenzymes.
• The drug's inhibitory mechanism is primarily competitive with key cofactors or substrates.
• These findings suggest potential off-target effects of indomethacin beyond its known anti-inflammatory actions.