Polyphenol oxidase: Difference between revisions

{{Use dmy dates|date=1st November 20132018}}

Tyrosine is a key compound of pigmentation/browning reaction through the action of polyphenol oxidase. Discrimination of this pigmentation reaction is responsible for various types of diseases and disorders.<ref name=":0">{{Cite web|url=https://scholar.google.co.in/citations?user=D0mEhNEAAAAJ&hl=en|title=Separation of polyphenol oxidase and its inhibitor from onion leaves on Lignin Column|last=Anita Goswami-Giri, Neha Sawant|first=|date=|website=|archive-url=|archive-date=|dead-url=|access-date=}}</ref>There are two types of inhibitor of PPO, those competitive to oxygen in the copper site of the enzyme and those competitive to phenolics. [[Tentoxin]] has also been used in recent research to eliminate the PPO activity from seedlings of higher plants.<ref name="Duke_1982">{{cite journal |vauthors=Duke SO, Vaughn KC | title = Lack of involvement of polyphenol oxidase in ortho-hydroxylation of phenolic compounds in mung bean seedlings | journal = Physiologia Plantarum |date=April 1982 | volume = 54 | issue = 4 | pages = 381–385 | doi = 10.1111/j.1399-3054.1982.tb00696.x }}</ref> [[Tropolone]] is a grape polyphenol oxidase [[Enzyme inhibitor|inhibitor]].<ref>Time-dependent inhibition of grape polyphenol oxidase by tropolone. Edelmira Valero, Manuela Garcia-Moreno, Ramon Varon and Francisco Garcia-Carmona, J. Agric. Food Chem., 1991, 39 (6), pp 1043–1046, {{doi|10.1021/jf00006a007}}</ref> Another inhibitor of this enzyme is [[potassium pyrosulphite]] (K₂S₂O₅).<ref name="Del_Signore_1997">{{cite journal |vauthors=Del Signore A, Romeoa F, Giaccio M |title=Content of phenolic substances in basidiomycetes | journal = Mycological Research |date=May 1997 | volume = 101 | issue = 5 | pages = 552–556 | doi = 10.1017/S0953756296003206}}</ref> Banana root PPO is strongly inhibited by [[dithiothreitol]] and [[sodium metabisulfite]].<ref>{{cite journal | vauthors = Wuyts N, De Waele D, Swennen R | title = Extraction and partial characterization of polyphenol oxidase from banana (Musa acuminata Grande naine) roots | journal = Plant Physiology and Biochemistry | volume = 44 | issue = 5-6 | pages = 308–14 | year = 2006 | pmid = 16814556 | doi = 10.1016/j.plaphy.2006.06.005 }}</ref> Endogenous proteinous fractions act endogenous inhibitor/regulator of onion leaves PPO (monophenol monooxygenase and o-diphenol oxidase)<ref name=":0" /> [[Potassium dithionite]] (or potassium hydrosulfite) is also an inhibitor of PPO.