Влияние химической модификации остатков триптофана на каталитическую активность глутамин(аспарагин)азы из Pseudomonas aurantiaca

Изучали изменение каталитических свойств глутамин(асиарагин)азы из Pseudomonas aurantiaca 875 (ГА) в зависимости от степени модификации (окисления) остатков триптофана в молекуле фермента. Для модификации этих остатков была использована высокоспецифичная система: перекись водорода-диоксан-бикарбонатный буфер 8, 5. а также о-нитрофенилсульфенилхлорид. Модификации подвергались только остатки триптофана.

Effect of Chemical Modification of Tryptophan Residues on the Catalytic Activity of Glutamin(asparagin)ase from Pseudomonas aurantiaca

Changes in catalytic properties of glutamin(aspsragin)asc from Pseudomonas aurantiaca 875 depending on the degree of modification (oxidation) of tryptophan residues in the enzyme molecule were analyzed. For such a modification the high specific system was applied: hydrogen peroxide:dioxan:bicartionat buffer (pH 8. 5) and o-nitrophenylsulfenil chloride. The experimental conditions allowed to measure the modification from 1 to 8 tryptophan residues (practically all of them) in I M of enzyme molecule. Experimental data show that modification only one tryptophan residues leads to the almost complete inactivation of enzyme activity in relation to the substrates. Data obtained suggest on the essential significant of tryptophan in catalytical reaction; it means that one from eight tryptophan residues takes part, either in the structure of enzyme and correspondingly catalyze directly the reaction or in structure of nearest environment of active site stabilizing the catalytical active conformation of enzyme molecule.