Untitled

Inhibition of Peroxidase-Catalyzed Oxidation of Chromogenic Substrates by Propyl Gallate and Its Polydisulfide

“…Figure 2b presents Dixon plots of the dependences of the inverse value of the initial rate on PG concentration; the value K i = 62 µM, derived from the figure data, indicates that PG inhibits peroxidase-catalyzed ABTS oxidation with medium efficiency. Figure 3a shows kinetic curves of accumulation of the ABTS oxidation product in the absence of inhibitors (1) and in the presence of increasing concentrations of PGPDS (2)(3)(4)(5)(6)(7)(8)(9)(10). The duration of the induction periods, ∆τ, depends linearly on the initial concentration of PGPDS (Fig.…”

“…The schemes and mechanisms of combined oxidation of amines (AmNH 2 ) and phenols (PhOH) have been the subject of discussion in our prior reports [1,[3][4][5][6][7][8][9][10][11][12]. This complex process appears as an array of enzymatic and non-enzymatic reactions occurring in sequence and in parallel, and its overall direction and character are largely determined by the non-enzymatic exchange reaction involving aminyl and phenoxyl free radicals (discovered by Emanuel et al [23,24]:…”

“…Largescale automated EIAs require stop-reagents capable of terminating peroxidase-catalyzed oxidation of chromogenic substrates. Systematic kinetic studies of peroxidase-catalyzed oxidation of TMB and OPD in the presence of phenols have been conducted in our laboratory over the last 15 years [1,3]. We were able to demonstrate that peroxidase-catalyzed oxidation of TMB is inhibited (with variable efficiency) by gallic acid and its polydisulfide (GAPDS) [4][5][6]; 2-amino-4-nitrophenol and its polydisulfide [7,8]; 1-amino-2-naphthole-4-sulfonate and its polydisulfide [9]; 2,4-dinitrosoresorcinol and polydisulfides of resorcinol and 2,4-dinitroresorcinol [10]; 3-aminophenol polydisulfide [11]; and propyl gallate (PG) [12].…”

“…Oxidation of TMB or OPD in combination with a substituted phenol or polyphenol was characterized quantitatively by two characteristics: the constant of inhibition ( K i ) and the stoichiometric inhibition factor ( f ), the latter being equal to the number of free radicals extinguished per molecule of an inhibitor [1,[3][4][5][6][7][8][9][10][11][12]. The highest inhibitory activity was exhibited by resorcinol polydisulfide (RPDS) ( K i = 0.78 µ M; f = 76) [10] and GAPDS ( K i = 1.33 µ M; f = 36) [5,6], which may be used for complete termination of peroxidase-catalyzed TMB oxidation in the course of EIAs of various antigens.…”

Inhibition of peroxidase-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine by aminophenols

“…

Peroxidase catalyzed amine oxidation in the pres ence of phenols is a fundamental problem of peroxidase catalysis [1,2]. This problem is also of practical impor tance because amine-phenol pairs are used in enzyme immunoassay of many antigens [3] and in general antiox idant activity tests of human and animal biological liquids, food, wines, juices, and natural biopreparations in which an amine is a substrate and phenol is a "calibrating" inhi bitor (its antiradical activity is compared with the inhibito ry properties of the analyzed biological liquids) ([4, 5] and references cited therein).

…”