Department of Biology, Roudehen Branch, Islamic Azad University, Roudehen, Iran.
J Food Biochem. 2019 Feb;43(2):e12724. doi: 10.1111/jfbc.12724. Epub 2018 Nov 8.
Peroxidase as a heme-containing metalloprotein, is an important enzyme for food industries. Hence, the current study is aimed to evaluate the inhibitory properties of zinc ion in terms of activity and thermal stability of horseradish peroxidase (HRP) in the range of 40-70°C for 1-45 min. The results showed that zinc ion potently inhibited HRP activity by noncompetitive mechanism. The thermal inactivation of enzyme followed first-order reaction kinetics in the presence of ZnCl up to 300 μM. However, higher concentrations of Zn -induced irregularities in HRP thermo inactivation pattern from first-order kinetics. According to the kinetic parameters, K and E , the rate of reactivation of HRP may be dependent on the amount of zinc ion, inactivation time, and heating duration. PRACTICAL APPLICATIONS: Thermal inactivation kinetics of HRP was investigated in the presence of Zn . The results showed that thermal inactivation of HRP followed first-order kinetics for up to 300 μM of Zn . HRP inactivation was consistent with biphasic models for higher concentrations of Zn at 60°C. The transition free energy of inactivation confirmed that zinc ion increased the enzyme unfolding transition states stability as denatured structure of HRP is more favorable than native one in this condition. Moreover, reactivation potential of enzyme decreased by increasing the zinc ion concentration.
过氧化物酶作为一种含铁金属蛋白，是食品工业中的重要酶。因此，本研究旨在评估锌离子在 40-70°C 范围内对辣根过氧化物酶（HRP）活性和热稳定性的抑制特性，时间为 1-45 分钟。结果表明，锌离子通过非竞争性机制强烈抑制 HRP 活性。在 ZnCl 存在下，酶的热失活遵循一级反应动力学，直至 300 μM。然而，较高浓度的 Zn 会导致 HRP 热失活动力学从一级动力学不规则。根据动力学参数 K 和 E ，HRP 的复活速率可能取决于锌离子的数量、失活时间和加热持续时间。
研究了 HRP 在 Zn 存在下的热失活动力学。结果表明，HRP 的热失活遵循一级动力学，直至 300 μM 的 Zn。对于 60°C 下更高浓度的 Zn，HRP 失活与两相模型一致。失活的自由能转变证实，锌离子增加了酶展开过渡态的稳定性，因为在这种条件下，HRP 的变性结构比天然结构更有利。此外，随着锌离子浓度的增加，酶的复活潜力降低。
