Activation of Peroxidase-Catalyzed Oxidation of 3,3´.5,5´-Tetramethylbenzidine with Poly(salicylic acid 5-aminodisulfide)

D. I. Metelitza^* and E. I. Karasyova

Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, ul. Akademika 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 September 27, 2001; Revision received February 5, 2002

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5-Aminosalicylic acid (5-ASA) inhibited by a mixed mechanism the peroxidase catalyzed oxidation of tetramethylbenzidine (TMB) in 0.015 M phosphate-citrate buffer (pH 6.4) supplemented with 5% DMSO and 5% DMF. Poly(salicylic acid 5-aminodisulfide) (poly(SAADS)) in 0.01 M phosphate buffer (pH 6.2-7.4) supplemented with 5% DMSO and 5% DMF effectively activated the peroxidase-catalyzed oxidation of TMB. The activation was quantitatively characterized by coefficients alpha (M^-1) determined at different pH values: alpha increased linearly with increase in pH up to the maximal value of 2.44*10⁵ M^-1 at pH 7.0. The activating effect of poly(SAADS) on the peroxidase-catalyzed oxidation of TMB is explained by the activator properties of polyelectrolyte, with its anionic form interacting with peroxidase sites responsible for the acid-base catalysis.

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KEY WORDS: horseradish peroxidase, tetramethylbenzidine, 5-aminosalicylic acid, poly(salicylic acid 5-aminodisulfide), activation, co-oxidation, inhibition of peroxidase-dependent reactions

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