Abstract
Polyphenol oxidase (PPO, E.C. 1.14.18.1) is a nearly ubiquitous enzyme that is widely distributed among organisms. Despite its widespread distribution, the role of PPO in plants has not been thoroughly elucidated. In this study, we report for the absence of PPO in Cynomorium coccineum, a holoparasitic plant adapted to withstand unfavorable climatic conditions, growing in Mediterranean countries and amply used in traditional medicine. The lack of PPO has been demonstrated by the absence of enzymatic activity with various substrates, by the lack of immunohistochemical detection of the enzyme, and by the absence of the PPO gene and, consequently, its expression. The results obtained in our work allow us to exclude the presence of the PPO activity (both latent and mature forms of the enzyme), as well as of one or more genes coding for PPO in C. coccineum. Finally, we discuss the possible significance of PPO deficiency in parasitic plants adapted to abiotic stress.
Highlights
Polyphenol oxidases (PPO, EC 1.14.18.1) are type-3 copper monooxygenases found in animals, plants, lichens, and bacteria [1,2,3,4]
To test the hypothesis of an activity hidden by the presence of an inhibitor, we dialyzed an aliquot of homogenate
Giant fennel was chosen because its PPO activity has characterized [26]; it is possible to find this plant in adjacent areas and in the same3 of 13
Summary
Polyphenol oxidases (PPO, EC 1.14.18.1) are type-3 copper monooxygenases found in animals, plants, lichens, and bacteria [1,2,3,4]. These enzymes catalyze the o-hydroxylation of monophenols to o-catechols (monophenolase or cresolase activity) and the oxidation of the latter to the corresponding o-quinones (diphenolase or catechol oxidase activity) [5]. An interesting role suggested for plant PPOs is the ability to repair damaged cells helping plants defend themselves against some external stress [11]. Exposure of wheat plants to stress from some heavy metals decreased PPO activity [12]
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