title: [Chemical modification of lysine epsilon-NH2-groups in horseradish peroxidase. Its effect on enzyme stability. Temperature dependence of thermo-inactivation constants for native and modified peroxidase].
abstract: Thermostability of horseradish peroxidase modified by acetic, propionic, butyric, valeric and succinic anhydrides and trinitrobenzolsulfonic acid (TNBS) is studied within the temperature range of 56-80 degrees C. Acylation of 4 amino groups and arylation of 3 amino groups with TNBS are found to stabilize the enzyme, while modification of 6 groups decreases the enzyme stability. Chemical modification of peroxidase does not change its pH-dependence with respect to enzyme thermostability. Thermodynamic activation parameters of irreversible thermoinactivation are determined for native and modified peroxidase. Native peroxidase has deltaH not equal to = 30+/-1 kcal/mole and deltaS not equal to = 14 e. e.; modified by acid anhydrides peroxidase has deltaH not equal to within 64-87 kcal/mole and deltaS not equal to within 110-178 e. e. depending on the nature of a modifying agent. The effect of the structure of a radical introduced into the enzyme molecule, and of a number of modified epsilon-amino groups on thermoinactivation deltaH not equal to and deltaS not equal to values is discussed.
mesh_terms: D000215:Acylation; D055598:Chemical Phenomena; D002621:Chemistry; D004355:Drug Stability; D004789:Enzyme Activation; D006735:Horseradish Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008239:Lysine; D010544:Peroxidases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013696:Temperature; D013816:Thermodynamics
chemical_list: D006735:Horseradish Peroxidase; D010544:Peroxidases; D008239:Lysine
vernacular_title: Khimicheskaia modifikatsiia epsilon-NH2-grupp ostatkov lizina v peroksidaze iz khrena. Vliianie ee na termicheskuiu stabil'nost' fermenta temperaturnye zavisimosti konstant termoinaktivatsii nativnoi i modifitsirovannoĭ peroksidazy.