Mechanism-based inhibition of lactoperoxidase by thiocarbamide goitrogens.
The irreversible inactivation of bovine lactoperoxidase by thiocarbamide goitrogens was measured, and the kinetics were consistent with a mechanism-based (suicide) mode. Sulfide ion inactivated, 2-mercaptobenzimidazole-inactivated, and 1-methyl-2-mercaptoimidazole-inactivated lactoperoxidases have different visible spectra, suggesting different products were formed. The results support a mechanism in which reactive intermediates are formed by S-oxygenation reactions catalyzed by lactoperoxidase compound II. It is proposed that the reaction of electron-deficient intermediates with the heme prosthetic group is responsible for the observed spectral changes and inactivation by thiocarbamides.
D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology*; D002417:Cattle; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D007784:Lactoperoxidase / Q000037:antagonists & inhibitors*; D008713:Methimazole / Q000494:pharmacology*; D010544:Peroxidases / Q000037:antagonists & inhibitors*; D011485:Protein Binding; D013053:Spectrophotometry; D013329:Structure-Activity Relationship
D001562:Benzimidazoles; D007093:Imidazoles; D008713:Methimazole; C030698:2-mercaptobenzimidazole; C050222:5-nitro-2-mercaptobenzimidazole; D007784:Lactoperoxidase; D010544:Peroxidases