Lactoperoxidase, an antimicrobial enzyme, is inhibited by some indazoles

Lactoperoxidase (LPO) has bactericidal and bacteriostatic activity on various microorganisms and it creates a natural antimicrobial defense system. So, LPO is one of the essential enzyme in biological systems and the protection of the LPO activity is extremely important for the immune system. Because of these features, the protection of the activity of the LPO has vital importance for the health of the organisms. Also, LPO is used in various sectors from cosmetics industry to agriculture industry due to its broad antimicrobial properties. Therefore, the identification of inhibitors and activators of the LPO is becoming increasingly important. In present study we aimed to investigate the inhibitory effects of some indazoles [1H-indazole (1a), 4-Bromo-1H-indazole (2a), 6-Bromo-1H-indazole (3a), 7-Bromo-1H-indazole (4a), 4-chloro-1H-indazole (5a), 6-chloro-1H-indazole (6a), 7-chloro-1H-indazole (7a), 4-fluoro-1H-indazole (8a), 6-fluoro-1H-indazole (9a), 7-fluoro-1H-indazole (10a)] on bovine milk LPO. Indazole derivatives are heterocyclic organic molecules with a wide range of biological activity. For this aim, bovine milk LPO was purified using Sepharose-4B-l-tyrosine-5-amino-2-methyl benzenesulfonamide affinity chromatography method. Then, the potential inhibitory effects of indazoles on LPO activity were investigated. K_i values were calculated for each indazole molecule. K_i values were ranging from 4.10 to 252.78 µM for 1a to10a. All of the indazole molecules we studied showed strong inhibitory effect on LPO activity. Also we determined inhibition types of the indazoles to clarify the mechanisms of inhibition.