The enzyme PPO catalyzes the oxidation of phenolic substrates into reactive quinones which polymerize into dark pigments (e.g., melanin) or attach to other biomolecules. Changes in PPO expression have been observed in response to biotic stress (pathogen attack) and abiotic stress (e.g., saline irrigation). The characterization of PPO is of great interest for the food industry, since PPO is responsible for the browning of bruised or cut vegetables and fruit. PPO is also employed in various biotechnological applications, such as waste water treatment or the biosynthesis of the Parkinson’s drug L-DOPA.
PPO was a research topic of several master theses and is also the main topic of the course Chem443 Biochemistry Laboratory I.
Lalla Aida Fall. "Purification and Characterization of Polyphenol Oxidase of Hybrids Poplar Leaves". (2016) https://scholarworks.calstate.edu/downloads/44558f25j
Karishma Kaur. "Survey of Polyphenol Oxidase Enzymes in the Brassicaceae Plant Family." (2016) https://scholarworks.calstate.edu/downloads/6w924c561
Robin Baginki. "Characterization and Identification of an Enzyme from Thermomicrobium Roseum with Activity towards Catechol." (2015) https://csueastbay-dspace.calstate.edu/bitstream/handle/10211.3/158628/Robin.Lisa.BaginskiThesis.pdf
Summervir Cheema. "Characterization of Polyphenol Oxidase in Ataulfo Mango." (2015) https://csueastbay-dspace.calstate.edu/bitstream/handle/10211.3/158620/Summervir.CheemaThesis.pdf
Chem443 was designed to encompass one project dedicated to the purification (ammonium sulfate fractionation, ion exchange chromatography, hydrophobic interaction chromatography) and characterization (enzyme kinetics, protein electrophoresis) of PPO.
This video lecture (Fall 2020, Chem443) introduces the protein sequence and structure of polyphenol oxidase.