The inducible expression of polyphenol oxidase (PPO), a presumed antiherbivore enzyme, was examined in hybrid poplar (Populus trichocarpa x Populus deltoides). Following mechanical wounding simulating insect damage, PPO activity increased dramatically in wounded and unwounded leaves on wounded plants beginning at 24 and 48 h, respectively. A hybrid poplar PPO cDNA was isolated and its nucleotid...

A comparative study of polyphenol oxidase (PPO) from two varieties of brinjal (local long green-bili badnea and purple-gundu badne) was conducted to determine differences and similarities of some of the characteristics of the PPO enzymes in terms of temperature and pH optima, substrate specificity, thermal inactivation and potency of some PPO inhibitors. PPO was partially purified by ammonium s...

Sodium chlorite (SC) is a well known anti-microbial agent and its strong inhibitory effect on enzymatic browning of fresh-cut produce has recently been identified. We investigated the effect of SC on polyphenol oxidase (PPO) and its substrate, chlorogenic acid (CA), as it relates to the mechanisms of browning inhibition by SC. Results indicate that the browning reaction of CA (1.0mM) catalyzed ...

Two polyphenol oxidase isoforms with distinct expression patterns were identified in hybrid poplar (Populus trichocarpaxP. deltoides). PPO-1, corresponding to the previously cloned PtdPPO (Constabel et al., Plant Physiol. 124: 285-295) was primarily leaf tissue-specific and detected only after wounding. PPO-2 was expressed constitutively in all tissue types tested except mature leaves, with hig...

Peroxidases (POD) and polyphenol oxidase (PPO) are enzymes that are well known to be involved in the enzymatic browning reaction of fruits and vegetables with different catalytic mechanisms. Both enzymes have some common substrates, but each also has its specific substrates. In our computational study, the amino acid sequence of grape peroxidase (ABX) was used for the construction of models emp...

Heavy metals are one of the major groups of contaminants in the environment and many of them are toxic even at very low concentration in plants and animals. However, some metals play important roles in the biological function of many enzymes in living organisms. Metals such as zinc, iron, and cooper are important for survival and activity of enzymes in plants, however heavy metals can inhibit e...

Polyphenol oxidase (PPO) (monophenol, o-diphenol: oxygen oxidoreductase; EC 1.14.18.1) is a binuclear copper-cluster-containing monooxygenase ubiquitously present in biological systems (1, 2). PPO may be distinguished from the related oxidase laccase [p-diphenol:oxygen oxidoreductase; EC 1.10.3.2] by its substrate specificity and the type and number of catalytic coppers. PPO catalyzes the oxida...

KOCAQALISKAN I., DEMIR Y. & KABAR, K. 1995. A study on polyphenol oxidase activity during seed germination. Phyton (Horn, Austria) 35 (1): 37-43. English with German summary. In this work, polphenol oxidase (PPO) activities, when used four different substrates (dopa,catechol,caffeic acid, tyrosine) oxidizing activities, during seed germination of six different plants were studied in the embryos...

Because direct oxidation of flavonols by polyphenol oxidase (PPO) has not previously been reported and, given the importance of flavonols, the ability of broad bean seed PPO to oxidize the flavonol quercetin was studied. The reaction was followed by recording spectral changes with time. Maximal spectral changes were observed at 291 nm (increase) and at 372 nm (decrease). The presence of two iso...