Activation of Peroxidase-Catalyzed Oxidation of Aromatic Amines with 2-Aminothiazole and Melamine

E. I. Karasyova, I. V. Naumchik, and D. I. Metelitza^*

Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, ul. Kuprevicha 5/2, Minsk, 220141 Belarus; fax: (375) (172) 63-7274; E-mail: metelitza@iboch.bas-net.by

^* To whom correspondence should be addressed.

Received November 8, 2001; Revision received January 4, 2002

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The peroxidase-catalyzed oxidation of 3,3´,5,5´-tetramethylbenzidine (TMB), ortho-phenylenediamine (PDA), and 5-aminosalicylic acid (5-ASA) is significantly accelerated in the presence of 2-aminothiazole (AT) and melamine (MA), and an increase in their concentrations is associated with a parallel increase in the k_cat and K_m values for TMB and PDA. The activation of the peroxidase-catalyzed oxidation of TMB and PDA is quantitatively characterized by a coefficient (degree) alpha (M^-1) which significantly depends on pH in the range 6.2-6.4, 6.4-7.4, and 6.0-7.4 for the TMB-AT, TMB-MA, and PDA-MA pairs, respectively. An increase in the coefficient alpha with increase in pH confirms nucleophilicity of activation of the peroxidase-catalyzed oxidation of the aromatic amines in the presence of AT and MA. Under optimal conditions the coefficients alpha for the TMB-AT, PDA-AT, TMB-MA, and PDA-MA pairs vary in the limits of (1.90-3.53)*10³ M^-1.

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KEY WORDS: horseradish peroxidase, tetramethylbenzidine, ortho-phenylenediamine, 5-aminosalicylic acid, activation of oxidation, 2-aminothiazole, melamine, nucleophilic catalysis

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