Mechanism-based inhibition of lactoperoxidase by thiocarbamide goitrogens

Area of Science:

• Biochemistry
• Enzymology

Background:

• Lactoperoxidase (LPO) is a key enzyme in the innate immune system.
• Thiocarbamide goitrogens are known to interfere with thyroid hormone synthesis.
• Understanding LPO inactivation mechanisms is crucial for assessing potential drug interactions.

Purpose of the Study:

• To investigate the mechanism of irreversible inactivation of bovine lactoperoxidase by thiocarbamide goitrogens.
• To characterize the spectral changes associated with enzyme inactivation.
• To elucidate the role of reactive intermediates in the inactivation process.

Main Methods:

• Enzyme kinetics assays to measure inactivation rates.
• Spectroscopic analysis (UV-Visible) to detect spectral changes.
• Proposed mechanistic studies involving S-oxygenation and reactive intermediates.

Main Results:

• Bovine lactoperoxidase inactivation by thiocarbamides follows a mechanism-based (suicide) inhibition.
• Different thiocarbamides produced distinct visible spectra upon inactivation, indicating varied reaction products.
• Evidence suggests S-oxygenation reactions catalyzed by lactoperoxidase compound II form reactive intermediates.

Conclusions:

• The reaction mechanism involves S-oxygenation and the formation of reactive intermediates.
• These intermediates interact with the heme prosthetic group, causing spectral shifts and enzyme inactivation.
• This study provides insights into the molecular basis of lactoperoxidase inhibition by goitrogens.