Yemenicioğlu Ahmet, Cemeroğlu Bekir
Department of Food Engineering, Faculty of Agriculture, Ankara University, 06110 Dişkapi, Ankara, Turkey.
J Agric Food Chem. 2003 Apr 9;51(8):2371-9. doi: 10.1021/jf025988q.
Destabilization of thermostable polyphenol oxidase (TS-PPO) during the ripening of peaches has been previously shown (Yemenicioğlu, A.; Cemeroğlu, B. Tr. J. Agric. For. 1998, 22, 261-265). This work studied the effect of ripening on thermal stability of apricot PPO for three different cultivars. Kabaaşi cultivar contained thermolabile PPO, whereas TS-PPO appeared in Hacihaliloğlu and Cataloğlu cultivars. The TS-PPO showed biphasic inactivation curves, and its D and z values between 60 and 90 degrees C varied in the ranges of 357-1.12 min and 11.9-12.7 degrees C, respectively. In Hacihaliloğlu cultivar the TS-PPO was very consistent and existed at all stages of ripening, whereas in Cataloğlu cultivar it appeared only at the half-ripe stage. The loss of consistent TS-PPO in Hacihaliloğlu apricots after partial purification by acetone precipitation and DEAE-cellulose chromatography suggested the non-covalent nature of its stabilization. The main purified fractions (F1 and F2) showed monophasic inactivation curves with similar thermal inactivation parameters (z(F1) = 10.4 degrees C, z(F2) = 10.1 degrees C). However, their kinetic properties against catechol (K(mF1) = 61 mM, K(mF2) = 122.7 mM) and substrate specificities were considerably different. The results of this study showed the presence of TS-PPO forming and destabilizing mechanisms in apricots. Further studies are needed for the solution of these mechanisms and to develop some new strategies that may be utilized by molecular techniques for a planned production of apricot cultivars provided with heat labile but normal PPO activity.
桃子成熟过程中热稳定多酚氧化酶（TS-PPO）的稳定性下降此前已有报道（Yemenicioğlu, A.; Cemeroğlu, B. Tr. J. Agric. For. 1998, 22, 261 - 265）。本研究考察了成熟对三个不同杏品种中PPO热稳定性的影响。Kabaaşi品种含有热不稳定PPO，而Hacihaliloğlu和Cataloğlu品种中出现了TS-PPO。TS-PPO呈现双相失活曲线，其在60至90摄氏度之间的D值和z值分别在357 - 1.12分钟和11.9 - 12.7摄氏度范围内变化。在Hacihaliloğlu品种中，TS-PPO非常稳定，在成熟的各个阶段都存在，而在Cataloğlu品种中，它仅在半熟阶段出现。通过丙酮沉淀和DEAE - 纤维素色谱法对Hacihaliloğlu杏进行部分纯化后，稳定的TS-PPO消失，这表明其稳定性具有非共价性质。主要纯化组分（F1和F2）呈现单相失活曲线，具有相似的热失活参数（z(F1) = 10.4摄氏度，z(F2) = 10.1摄氏度）。然而，它们对儿茶酚的动力学性质（K(mF1) = 61 mM，K(mF2) = 122.7 mM）和底物特异性有很大差异。本研究结果表明杏中存在TS-PPO形成和失稳机制。需要进一步研究以解决这些机制，并开发一些新策略，这些策略可通过分子技术用于有计划地生产具有热不稳定但正常PPO活性的杏品种。
