Polyphenoloxidases from Williams Pear (Pyrus communis L, cv Williams): Activation, Purification and Some Properties

Alternative pathway implicated as an influencing factor in the synthesis of theaflavin

“…The specific activity of the crude PPO was 14613 units/mg while the specific activity of the pooled fractions following affinity chromatography was 44059 units/mg and therefore resulting in a 3 fold purification of the PPO from Forelle pear. This was consistent with the identification of the presence of isoenzymes in PPO purified from d'Anjou pear and Williams pear in which three isoenzymes were detected [10,41]. From the pH activity profile of Forelle pear PPO, the enzyme had an observed optimum pH at 5, followed by a sharp decrease in activity (units) between pH 5 and 5.5, and a small shoulder was present at pH 6.5 ( Figure 5).…”

Some Biochemical properties of polyphenoloxidase from spearmint (Mentha arvensis)

“…The PPO activity can be assayed in the presence or absence of SDS (Moore and Flurkey, 1990;Nunez-Delicado et al, 2003;Concellón et al, 2004). The effect of SDS in the activation process results from a conformational change due to the binding of a small quantity of SDS to the active site (Moore andFlurkey, 1990, Gauillard andRichard-Forget, 1997). Nunez-Delicado et al (2003) related a latent form of PPO in persimmon fruit that was optimally activated by the presence of 1 mM SDS; the latent enzyme presented monophenolase and diphenolase activities and in the absence of SDS the enzyme activity increased at acidic pH.…”

“…It is well known that browning reactions, initiated by the enzyme, occur generally post-harvest when the tissues are exposed either to stress conditions, to deterioration or during handling, storage and processing (Tomás-Barberán and Espín, 2001). PPO has been extensively studied and characterized in a variety of tissues, as sweet potato (Lourenço et al, 1992) potato and taro (Duangmal and Owusu Apenten, 1999); egg plant (Concellón et al, 2004); palmito (Lourenço et al, 1990); apple (Nicolas et al, 1994); pears (Gauillard and Richard-Forget, 1997); grapes (Rapeanu et al, 2006); herbs (Arslan et al, 1997); tea leaves (Halder et al, 1998); peppermint (Kavrayan and Aydemir, 2001); oregano (Dogan et al, 2005) and artichoke (Aydemir, 2004). Mentha arvensis is the Mentha specie extensively cultivated in Brazil for the industrial and home uses as tea infusion.…”

Purification and Characterization of Polyphenoloxidase from Guava Infected with Fruit-rot Disease

“…There are several other reports that described high-temperature lability of PPO from other sources to the same temperature range (Fujita and Tono, 1988;Lourenco et al, 1990). The kinetic parameters of guava PPO was studied against a single substrate, but the result showed a unique similarity with other reports (Gauillard and Richard-Forget, 1997). Though we did not investigate the effect of metal ion on the activity of the enzyme, inactivation in presence of EDTA is a clear indication of metal ion dependence of the enzyme.…”