Carvajal Nelson, Uribe Elena, López Vasthi, Salas Mónica
Departamento de Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
Protein J. 2004 Apr;23(3):179-83. doi: 10.1023/b:jopc.0000026413.68088.e0.
Human liver arginase (EC 3.5.3.1) was totally inactivated by incubation with Woodward's reagent K (WRK). The inactivation followed pseudo-first-order kinetics, and the order of the inactivation was close to 1, consistent with reaction of one molecule of WRK with one subunit molecule for inactivation. The effect was totally reversed by 0.5 M hydroxylamine, and reactivated species were inactivated again by a second incubation with WRK. The pH dependence of the pseudo--first-order rate constants of inactivation indicated the participation of a ionizable residue with a pKa of 6.3 at 25 degrees C. Replacement of His141 with phenylalanine rendered the enzyme totally resistant to the inactivation. We conclude that His141 is the residue whose chemical modification with WRK inactivates the enzyme.
人肝脏精氨酸酶（EC 3.5.3.1）与伍德沃德试剂K（WRK）孵育后完全失活。失活遵循假一级动力学，失活级数接近1，这与一分子WRK与一个亚基分子反应导致失活一致。0.5 M羟胺可完全逆转这种效应，重新激活的酶在再次与WRK孵育时会再次失活。失活的假一级速率常数的pH依赖性表明在25℃下有一个pKa为6.3的可电离残基参与其中。用苯丙氨酸取代His141使该酶完全抗失活。我们得出结论，His141是其与WRK的化学修饰使酶失活的残基。
