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Polydisulfides of substituted phenols as effective protectors of peroxidase against inactivation by ultrasonic cavitation
Authors:Grintsevich E E  Adzerikho I E  Mrochek A G  Metelitza D I
Institution:(1) Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, ul. Kuprevicha 5/2, Minsk, 220141, Belarus;(2) Belorussian State Institute of Physician Improvement, ul. P. Brovki 3, Minsk, 220714, Belarus
Abstract:Kinetics of inactivation of horseradish peroxidase (HP) induced by low-frequency ultrasonic (US) treatment (27 kHz) with the specific power of 60 W/cm2 were studied in phosphate (pH 7.4) and acetate (pH 5.2) buffers within the temperature range of 36.0 to 50.0°C and characterized by effective first-order rate constants of US inactivation k in (us) in min–1. Values of k in (us) depend on the specific ultrasonic power within the range of 20-60 W/cm2, on the concentration of HP, and on pH and temperature of the solutions. The activation energy of US inactivation of HP is 9.4 kcal/mole. Scavengers of HO· radicals, mannitol and dimethylformamide, significantly inhibit the US inactivation of HP at 36.0°C, whereas micromolar concentrations of polydisulfide of gallic acid (poly(DSG)) and of poly(2-aminodisulfide-4-nitrophenol) (poly(ADSNP)) virtually completely suppress the US inactivation of peroxidase at the ultrasonic power of 60 W/cm2 on the sonication of the enzyme solutions for more than 1 h at pH 5.2. Various complexes of poly(DSG) with human serum albumin effectively protect HP against the US inactivation in phosphate buffer (pH 7.4). The findings unambiguously confirm a free radical mechanism of the US inactivation of HP in aqueous solutions. Polydisulfides of substituted phenols are very effective protectors of peroxidase against inactivation caused by US cavitation.
Keywords:horseradish peroxidase  ultrasonic inactivation  inactivation kinetics  phenol polydisulfides  polydisulfide of gallic acid  poly(2-aminodisulfide-4-nitrophenol)  free radicals
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