[Human thyroid peroxidase: inhibition of iodide ion and 3,3',5,5'-tetramethylbenzidine hydrolysis by phenol antioxidants].
A comparative kinetic study on the poly(gallic acid disulfide) (poly(DSGA)) inhibition of the iodide ion oxidation and on the 2-hydroxy-3,5-di-tert-butyl-N-phenylaniline (butaminophene) inhibition of 3,3',5,5'-tetramethylbenzidine (TMB) oxidation involving human thyroid peroxidase (hTPO) and horseradish peroxidase (HRP) was performed. The inhibition processes were characterized with the inhibition constants Ki and stoichiometric inhibition coefficients f, indicating the number of radical particles perishing on one inhibitor molecule. In the case of poly(DSGA), the Ki values for the I- oxidation were 0.60 and 0.04 microM, and the coefficients f were 13.6 and 16.5 for hTPO and HRP, respectively, which evidences the regeneration and high effectiveness of the polymeric inhibitor. In the case of butaminophene, the Ki values for TMB oxidation were 38 and 46 microM for hTPO and HRP, respectively. The coefficients f were 1.33 and 1.47, respectively, to reveal that butaminophene does not regenerate. The inhibition mechanisms for I- and TMB oxidation involving the two peroxidases are discussed.
Grintsevich
E A
EA
Institute of Bioorganic Chemistry, Belarussian Academy of Sciences, ul. Kuprevicha 5/2, Minsk, 220141 Belarus.
Senchuk
V V
VV
Puchkaev
A V
AV
Shadyro
O I
OI
Metelitsa
D I
DI
D000838:Anions; D000975:Antioxidants / Q000737:chemistry*; D001560:Benzidines / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D006801:Humans; D007202:Indicators and Reagents; D007453:Iodide Peroxidase / Q000737:chemistry*; D007454:Iodides / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D010636:Phenols; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000737:chemistry*
C441091:2-hydroxy-3,5-dibutyl-N-phenylalanine; D000838:Anions; D000975:Antioxidants; D001560:Benzidines; D004220:Disulfides; D007202:Indicators and Reagents; D007454:Iodides; D010636:Phenols; C441090:poly(gallic acid disulfide); C021758:3,3',5,5'-tetramethylbenzidine; D010649:Phenylalanine; D005707:Gallic Acid; D006735:Horseradish Peroxidase; D007453:Iodide Peroxidase