Mechanism of Pressure-induced Reactivation of Inactivated Enzymes

为了阐明压力诱导失活酶再激活的机理，研究了压力对某些食品相关酶在3000大气压下活性的影响。(1)在3000大气压下加压灭活的过氧化氢酶(四聚体，剩余活力60%)在1000-2000大气压下再次加压10分钟，最高可达100%。冻融、冷冻干燥和热变性酶未观察到压力诱导复活现象。(2)在2500大气压下，β-半乳糖苷酶呈现可逆性压力失活，但释放压力后比活力升高。在500atm的重复加压最多将活性增加两倍。这些结果表明，该酶和过氧化氢酶的解离-缔合平衡(tetramer(〕SY.dblharw.〔)dimer(〕SY.dblharw.〔)monomer)的速率过程受到压力的影响，使平衡漂移到活性形式(四聚体)。(3)经压力和加热失活的醛缩酶和苹果酸脱氢酶不能通过再加压重新激活，而且这两种酶都是寡聚酶。单体酶、脂肪酶和过氧化物酶也不能在压力下重新激活。基于这些结果，压力诱导酶的重新激活在有限的条件下似乎是存在的，但结构的漂移(解离-缔合平衡)可能是压力重新激活的原因。

To elucidate the mechanism of pressure-induced reactivation of inactivated enzymes, the pressure effects on the activity of some food related enzymes were studied under pressures up to 3000 atm. (1) Catalase (tetramer, residual activity 60%) inactivated by pressuring at 3000 atm was reactivated, to at most 100%, by pressuring again at 1000-2000 atm for 10 min. Pressure-induced reactivation was not observed for freeze-thawing, freeze-drying and heat-denatured enzyme. (2) beta-galactosidase showed reversible pressure inactivation under 2500 atm but the specific activity was elevated after release of pressure. The repeating pressurization at 500 atm increased the activity at most two-fold. These results suggest that the rate processes of dissociation-association equiribrium (tetramer(〕SY.dblharw.〔)dimer(〕SY.dblharw.〔)monomer) of this enzyme as well as catalase are affected by pressure to drift the equilibrium to active form (tetramer). (3) Aldolase and malatedehydrogenase inactivated by pressure and heat were not reactivated by re-pressurization while both enzymes were also oligomeric ones. Monomeric enzymes, lipase and peroxidase were also not reactivated by pressure.Based on these results, the pressure-induced reactivation of enzymes seems to be phenomena under limited conditions, but the drift of structure (dissociation-association equilibrium) would be responsible for the reactivation by pressure.