Abstract—Polyphenol oxidase (EC.1.14.18.1) catalyzes the hydroxylation and oxidation of phenols to o-quinones leading to browning in plants. For polyphenol oxidase activity two pH optimum were observed, respectively at 6.7 and 8, that probably belong to at least two isoenzyme, so we named them ISOIPPO and ISOIIPPO respectively. These isoenzymes have different kinetics properties. Activation of PPO by SDS occurred below 1.3 mM SDS. ISOIPPO was much more active (86 times) with pyrogallol as substrate (4.9 unit/mg protein) in comparison of catechol (0.057 unit/mg protein) in presence of SDS. This comparison is 143 times in absence of SDS (3.3 and 0.023 unit/mg protein for pyrogallol and catechol, respectively). SDS activation probably alters both its enzymatic and physical characteristics. ISOIIPPO activity gradually increased during development of tomatoes from green to ripe, but ISOIPPO activity is nearly constant during development. PPO are believed to play physiological roles both in preventing insects and microorganisms from attacking plant and as part of the wound response of plant by its phenolic content, so these roles are more important for ISOIIPPO than ISOIPPO during changes from green to red tomatoes.

Index Terms—Solanum lycopersicum, pH, catechol, pyrogallol.

Shahryar Saeidian is with the Department Of Biology, Payame Noor University, 19395-4697, Tehran, Iran (e-mail: saeedyan@saghezpnu.ac).

Cite: Shahryar Saeidian, "Demonstration and Modification of the pH Profile of Polyphenol Oxidase in Solanum Lycopersicum," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 2, no. 6, pp. 385-388, 2012.