Consistency of Polyphenol Oxidase (PPO) Thermostability in Ripening Apricots (Prunus armeniaca L.):  Evidence for the Presence of Thermostable PPO Forming and Destabilizing Mechanisms in Apricots

Abstract

Destabilization of thermostable polyphenol oxidase (TS-PPO) during the ripening of peaches has been previously shown (Yemenicioǧ lu, A.; Cemeroǧ lu, 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. Kabaaş ı cultivar contained thermolabile PPO, whereas TS-PPO appeared in Hacıhaliloǧ lu and Ç ataloǧ lu cultivars. The TS-PPO showed biphasic inactivation curves, and its D and z values between 60 and 90°C varied in the ranges of 357-1.12 min and 11.9-12.7°C, respectively. In Hacıhaliloǧ lu cultivar the TS-PPO was very consistent and existed at all stages of ripening, whereas in Ç ataloǧ lu cultivar it appeared only at the half-ripe stage. The loss of consistent TS-PPO in Hacıhaliloǧ lu 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°C, z F2 ) 10.1°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.

Extraction and Characterization of Polyphenol Oxidase in Pawpaw (Asimina Triloba) Fruit

“…The K m of pawpaw fruit PPO was comparable with the K m of PPO from Spanish papaya (Cano et al. 1996), thymus (Dogan and Dogan 2004), apricots (Yemenicioglu and Cemeroglu 2003), marula fruit (Mdluli 2005), raspberry fruits (Gonzalez et al. 1999) and blackberry fruits (Gonzalez et al.…”

“…The V max and K m of the enzyme extract, based on the reaction rate in the linear range (0-60 s), were 0.1363/s and 0.3266 M, respectively. The K m of pawpaw fruit PPO was comparable with the K m of PPO from Spanish papaya (Cano et al 1996), thymus (Dogan and Dogan 2004), apricots (Yemenicioglu and Cemeroglu 2003), marula fruit (Mdluli 2005), raspberry fruits (Gonzalez et al 1999) and blackberry fruits (Gonzalez et al 2000). However, the specific K m value varies with fruit species, indicating different isoforms of PPO are produced by different plant species (Broothaerts et al 2000).…”

Partial purification and kinetic characterization of mushroom stem polyphenoloxidase and determination of its storage stability in different lyophilized forms

“…The same phenomenon was observed at pH 3.0 for the monophenolase activity of a wild edible mushroom (Macrolepiota mastoidea), while the enzyme showed highest stability at pH 4.0 [38]. The loss of labile monophenolase activity was also frequently observed during purification of PPO by different workers [2,39,40]. The pH effect on loss of monophenolase activity may be related to structural changes in enzyme.…”

Relationship between polyphenol oxidase activity and nutrition, maturity and quality parameters in flat peach

“…Changes in PPO activity during maturation have been described for several fruits, including apple, apricot, banana, grape, litchi, mango, melon, olive and also peach . In most cases, PPO activity progressively increases as fruit matures, experiencing the highest rise in the last days before harvest.…”