Polyphenol oxidase (PPO; also polyphenol oxidase i, chloroplastic), an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper per molecule.[1]
PPO may accept monophenols and/or o-diphenols as substrates.[2] The enzyme works by catalyzing the o-hydroxylation of monophenol molecules in which the benzene ring contains a single hydroxyl substituent to o-diphenols (phenol molecules containing two hydroxyl substituents at the 1, 2 positions, with no carbon between).[3] It can also further catalyse the oxidation of o-diphenols to produce o-quinones.[4] PPO catalyses the rapid polymerization of o-quinones to produce black, brown or red pigments (polyphenols) that cause fruit browning.
The amino acid tyrosine contains a single phenolic ring that may be oxidised by the action of PPOs to form o-quinone. Hence, PPOs may also be referred to as tyrosinases.[5]
Common foods producing the enzyme include mushrooms (Agaricus bisporus),[6][7] apples (Malus domestica),[8][9] avocados (Persea americana), and lettuce (Lactuca sativa).[10]
^"Polyphenol Oxidase". Worthington Enzyme Manual. Retrieved 13 September 2011.
^McLarin, Mark-Anthony; Leung, Ivanhoe K. H. (2020). "Substrate Specificity of Polyphenol Oxidase". Crit. Rev. Biochem. Mol. Biol.55 (3): 274–308. doi:10.1080/10409238.2020.1768209. PMID 32441137. S2CID 218831573.
^A Sánchez-Ferrer; J N Rodríguez-López; F García-Cánovas; F García-Carmona (1995). "Tyrosinase: A Comprehensive Review of Its Mechanism". Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1247 (1): 1–11. doi:10.1016/0167-4838(94)00204-t. PMID 7873577.
^C Eicken; B Krebs; J C Sacchettini (1999). "Catechol Oxidase - Structure and Activity". Current Opinion in Structural Biology. 9 (6): 677–683. doi:10.1016/s0959-440x(99)00029-9. PMID 10607672.
^Mayer AM (November 2006). "Polyphenol oxidases in plants and fungi: going places? A review". Phytochemistry. 67 (21): 2318–31. Bibcode:2006PChem..67.2318M. doi:10.1016/j.phytochem.2006.08.006. PMID 16973188.
^Mauracher SG, Molitor C, Michael C, Kragl M, Rizzi A, Rompel A (March 2014). "High level protein-purification allows the unambiguous polypeptide determination of latent isoform PPO4 of mushroom tyrosinase". Phytochemistry. 99: 14–25. Bibcode:2014PChem..99...14M. doi:10.1016/j.phytochem.2013.12.016. PMC 3969299. PMID 24461779.
^Mauracher SG, Molitor C, Al-Oweini R, Kortz U, Rompel A (September 2014). "Latent and active abPPO4 mushroom tyrosinase cocrystallized with hexatungstotellurate(VI) in a single crystal". Acta Crystallographica. Section D, Biological Crystallography. 70 (Pt 9): 2301–15. doi:10.1107/S1399004714013777. PMC 4157443. PMID 25195745.
^Kampatsikas I, Bijelic A, Pretzler M, Rompel A (August 2017). "Three recombinantly expressed apple tyrosinases suggest the amino acids responsible for mono- versus diphenolase activity in plant polyphenol oxidases". Scientific Reports. 7 (1): 8860. Bibcode:2017NatSR...7.8860K. doi:10.1038/s41598-017-08097-5. PMC 5562730. PMID 28821733.
^Kampatsikas I, Bijelic A, Pretzler M, Rompel A (May 2019). "A Peptide-Induced Self-Cleavage Reaction Initiates the Activation of Tyrosinase". Angewandte Chemie. 58 (22): 7475–7479. doi:10.1002/anie.201901332. PMC 6563526. PMID 30825403.
^Toledo L, Aguirre C (December 2017). "Enzymatic browning in avocado (Persea americana) revisited: History, advances, and future perspectives". Critical Reviews in Food Science and Nutrition. 57 (18): 3860–3872. doi:10.1080/10408398.2016.1175416. PMID 27172067. S2CID 205692816.
and 27 Related for: Polyphenol oxidase information
Polyphenoloxidase (PPO; also polyphenoloxidase i, chloroplastic), an enzyme involved in fruit browning, is a tetramer that contains four atoms of copper...
crustaceans polyphenols play a role in epicuticle hardening (sclerotization). The hardening of the cuticle is due to the presence of a polyphenoloxidase. In...
foods. Generally, it is a chemical reaction involving polyphenoloxidase (PPO), catechol oxidase, and other enzymes that create melanins and benzoquinone...
dark brown coloration. Polyphenoloxidases are a family of di-copper metalloenzymes that include tyrosinase and catechol oxidase. In plants, both enzymes...
phytochemicals, particularly polyphenols which are under preliminary research for their potential health effects. The enzyme polyphenoloxidase causes browning in...
Damaged pods brown more rapidly however, mainly due to the enzyme polyphenoloxidase. If stored fresh, the pods should be kept humid to prevent discoloration...
drying to decrease the rate of browning caused by the reaction between polyphenoloxidase and phenolic compounds. Sulfur dioxide also helps to preserve flavor...
similar to catechol oxidase, a related class of copper oxidase. Tyrosinases and catechol oxidases are collectively termed polyphenoloxidases. Tyrosinases have...
exposed to the oxygen in the air, the oxidative enzymes like polyphenoloxidase and catechol oxidase oxidize the fruit (electrons are lost to the air). Such...
for sour cream, tomatoes, basil, or peas. Due to the presence of polyphenoloxidase in the cells of avocado, exposure to oxygen in the air causes an enzymatic...
acids target enzymes that degrade fruits and vegetables, e.g., mono/polyphenoloxidase which turns surfaces of cut apples and potatoes brown. Ascorbic acid...
"Low-density lipoprotein antioxidant activity of phenolic compounds and polyphenoloxidase activity in selected clingstone peach cultivars". Journal of Agricultural...
in calories. It contains the prebiotic fiber inulin. It contains a polyphenoloxidase, which causes its darkened surface and muddy harshness by forming...
response from consuming eggplant: lipid transfer protein, profilin, polyphenoloxidase, and pollen reactions. A 2008 study of a sample of 741 people in India...
Tentoxin has also been used in recent research to eliminate the polyphenoloxidase (PPO) activity from seedlings of higher plants. PubChem. "Tentoxin"...
Fruits Inc. Specifically, gene silencing reduces the expression of polyphenoloxidase (PPO), thus delaying the onset of browning. It is the first genetically...
anthocyanins, and carotenoids in plants and animal tissues. In fruit juices, polyphenoloxidase (PPO) is the main enzyme responsible for causing browning and color...
Rescigno, Antonio (June 2013). "Isolation and characterization of polyphenoloxidase from Sardinian poisonous and non-poisonous chemotypes of Ferula communis...
by SmithKline Beecham HPV Vaccine proteins Polyphenoloxidases (PPOs): These include both catechol oxidases and tyrosinases. In additional to research...
derivatives. Other proteins include enzymes, such as catalase and polyphenoloxidase, which are important for the maturation of green coffee beans. Mature...
turns dark, because tyrosine presented in the potato is oxidised by polyphenoloxidase, which is located in the cellular juice. Therefore, cellular juice...
involves the oxidation of indole-5,6-quinone by the tyrosinase type polyphenoloxidase from tyrosine and catecholamines leading to the formation of catechol...
respond to parasite attack with a series of chemical defences, such as polyphenoloxidase, under the control of the jasmonic acid-insensitive (JA) and salicylic...
treatment, prevents enzymatic browning and inhibits activities of polyphenoloxidase. The process is economical. Osmotic dehydration depends on: Temperature...
Global Information