Polyphenol oxidase

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

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, and binding sites for two aromatic compounds and oxygen.[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]

Structure and function[edit]

PPO is listed as a morpheein, a protein that can form two or more different homo-oligomers (morpheein forms), but must come apart and change shape to convert between forms. It exists as a monomer, trimer, tetramer, octamer or dodecamer,[11][12] creating multiple functions.[13]

In plants, PPO is a plastidic enzyme with unclear synthesis and function. In functional chloroplasts, it may be involved in oxygen chemistry like mediation of pseudocyclic photophosphorylation.[14]

Enzyme nomenclature differentiates between monophenol oxidase enzymes (tyrosinases) and o-diphenol:oxygen oxidoreductase enzymes (catechol oxidases).

Distribution and applications[edit]

A mixture of monophenol oxidase and catechol oxidase enzymes is present in nearly all plant tissues, and can also be found in bacteria, animals, and fungi. In insects, cuticular polyphenol oxidases are present[15] and their products are responsible for desiccation tolerance.

Grape reaction product (2-S glutathionyl caftaric acid) is an oxidation compound produced by action of PPO on caftaric acid and found in wine. This compound production is responsible for the lower level of browning in certain white wines.

Plants make use of polyphenol oxidase as one in a suite of chemical defences against parasites.[16]

Inhibitors[edit]

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.[17] 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.[18] Tropolone is a grape polyphenol oxidase inhibitor.[19] Another inhibitor of this enzyme is potassium pyrosulphite (K2S2O5).[20] Banana root PPO is strongly inhibited by dithiothreitol and sodium metabisulfite.[21] Endogenous proteinous fractions act endogenous inhibitor/regulator of onion leaves PPO (monophenol monooxygenase and o-diphenol oxidase)[17] Potassium dithionite (or potassium hydrosulfite) is also an inhibitor of PPO.

Assays[edit]

Several assays were developed to monitor the activity of polyphenol oxidases and to evaluate the inhibition potency of polyphenol oxidase inhibitors. In particular, ultraviolet/visible (UV/Vis) spectrophotometry-based assays are widely applied.[22] The most common UV/Vis spectrophotometry assay involves the monitoring of the formation of o-quinones, which are the products of polyphenol oxidase-catalysed reactions, or the consumption of the substrate.[23] Alternative spectrophotometric method that involves the coupling of o-quinones with nucleophilic reagents such as 3-methyl-2-benzothiazolinonehydrazone hydrochloride (MBTH) was also used.[24] Other techniques, such as activity staining assays with the use of polyacrylamide gel electrophoresis,[25] tritium-based radioactive assays,[26] oxygen consumption assay,[27] and nuclear magnetic resonance (NMR)-based assay were also reported and used.[28]

Enzymatic browning[edit]

Polyphenol oxidase is an enzyme found throughout the plant and animal kingdoms,[29] including most fruits and vegetables.[30] PPO has importance to the food industry because it catalyzes enzymatic browning when tissue is damaged from bruising, compression or indentations, making the produce less marketable and causing economic loss.[29][30][31] Enzymatic browning due to PPO can also lead to loss of nutritional content in fruits and vegetables, further lowering their value.[10][29][30]

Because the substrates of these PPO reactions are located in the vacuoles of plant cells damaged mainly by improper harvesting, PPO initiates the chain of browning reactions.[31][32] Exposure to oxygen when sliced or pureed also leads to enzymatic browning by PPO in fruits and vegetables.[30] Examples in which the browning reaction catalyzed by PPO may be desirable include avocados, prunes, sultana grapes, black tea, and green coffee beans.[10][30]

In mango[edit]

In mangoes, PPO catalyzed enzymatic browning is mainly caused by sap burn which leads to skin browning.[citation needed] Catechol oxidase-type PPO is located in the chloroplasts of mango skin cells and its phenolic substrates in the vacuoles. Sap burn is therefore the initiating event of PPO in mango skin, as it breaks down cell compartments.[32] PPO is located in mango skin, sap and pulp, with highest activity levels in skin.[30]

In avocado[edit]

PPO in avocados causes rapid browning upon exposure to oxygen,[10] a multistep process involving oxidation reactions of both monophenols and polyphenols, resulting in o-quinone products subsequently converted irreversibly into brown polymeric pigments (melanins).[33]

In apple[edit]

Present in the chloroplasts and mitochondria of all parts of an apple,[30] PPO is the major enzyme responsible for enzymatic browning of apples.[34] Due to an increase in consumer demand for pre-prepared fruits and vegetables, a solution for enzymatic browning has been a targeted area of research and new product development.[35] As an example, pre-sliced apples are an appealing consumer product, but slicing apples induces PPO activity, leading to browning of the cut surfaces and lowering their esthetic quality.[35] Browning also occurs in apple juices and purees when poorly handled or processed.[36]

Arctic apples, an example of genetically modified fruit engineered to reduce PPO activity, are a suite of trademarked apples that contain a non-browning trait derived by gene silencing to suppress the expression of PPO, thus inhibiting fruit browning.[37]

In apricot[edit]

Apricot as a climacteric fruit undergoes fast post-harvest maturation. The latent PPO form can spontaneously activate during the first weeks of storage, generating the active enzyme with a molecular weight of 38 kDa.[38] Ascobic acid/proteases combinations constitute a promising practical anti-browning method as treated apricot purees preserved their color.[39]

In potato[edit]

Found in high concentrations in potato tuber peel and 1–2 mm of the outer cortex tissue, PPO is used in the potato as a defense against insect predation, leading to enzymatic browning from tissue damage.[citation needed] Damage in the skin tissue of potato tuber causes a disruption of cell compartmentation, resulting in browning. The brown or black pigments are produced from the reaction of PPO quinone products with amino acid groups in the tuber.[31] In potatoes, PPO genes are not only expressed in potato tubers, but also in leaves, petioles, flowers and roots.[31]

Related enzymes[edit]

Prophenoloxidase is a modified form of the complement response found in some invertebrates, including insects, crabs and worms.[40]

Hemocyanin is homologous to the phenol oxidases (e.g. tyrosinase) since both enzymes sharing type copper active site coordination. Hemocyanin also exhibits PPO activity, but with slowed kinetics from greater steric bulk at the active site. Partial denaturation actually improves hemocyanin’s PPO activity by providing greater access to the active site.[41]

Aureusidin synthase is homologous to plant polyphenol oxidase, but contains certain significant modifications.

Aurone synthase[42] catalyzes the formation of aurones. Aurone synthase purified from Coreopsis grandiflora shows weak tyrosinase activity against isoliquiritigenin, but the enzyme does not react with the classic tyrosinase substrates L-tyrosine and tyramine and must therefore be classified as catechol oxidase.[43]

See also[edit]

References[edit]

  1. ^ "Polyphenol Oxidase". Worthington Enzyme Manual. Retrieved 13 September 2011.
  2. ^ 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.CS1 maint: uses authors parameter (link)
  3. ^ A Sánchez-Ferrer, J N Rodríguez-López, F García-Cánovas, F García-Carmona (1995). "Tyrosinase: A Comprehensive Review of Its Mechanism". Biochim. Biophys. Acta. 1247 (1): 1–11. doi:10.1016/0167-4838(94)00204-t. PMID 7873577.CS1 maint: uses authors parameter (link)
  4. ^ 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.CS1 maint: uses authors parameter (link)
  5. ^ Mayer AM (November 2006). "Polyphenol oxidases in plants and fungi: going places? A review". Phytochemistry. 67 (21): 2318–31. doi:10.1016/j.phytochem.2006.08.006. PMID 16973188.
  6. ^ 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. doi:10.1016/j.phytochem.2013.12.016. PMC 3969299. PMID 24461779.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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.
  10. ^ a b c d 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.
  11. ^ Jolley RL, Mason HS (March 1965). "The Multiple Forms of Mushroom Tyrosinase. Interconversion". The Journal of Biological Chemistry. 240: PC1489–91. PMID 14284774.
  12. ^ Jolley RL, Robb DA, Mason HS (March 1969). "The multiple forms of mushroom tyrosinase. Association-dissociation phenomena". The Journal of Biological Chemistry. 244 (6): 1593–9. PMID 4975157.
  13. ^ Mallette MF, Dawson CR (August 1949). "On the nature of highly purified mushroom tyrosinase preparations". Archives of Biochemistry. 23 (1): 29–44. PMID 18135760.
  14. ^ Vaughn KC, Duke SO (1984). "Function of polyphenol oxidase in higher plants". Physiologia Plantarum. 60 (1): 106–112. doi:10.1111/j.1399-3054.1984.tb04258.x.
  15. ^ Sugumaran M, Lipke H (May 1983). "Quinone methide formation from 4-alkylcatechols: a novel reaction catalyzed by cuticular polyphenol oxidase". FEBS Letters. 155 (1): 65–68. doi:10.1016/0014-5793(83)80210-5. S2CID 84630585.
  16. ^ Thaler JS, Karban R, Ullman DE, Boege K, Bostock RM (April 2002). "Cross-talk between jasmonate and salicylate plant defense pathways: effects on several plant parasites". Oecologia. 131 (2): 227–235. Bibcode:2002Oecol.131..227T. doi:10.1007/s00442-002-0885-9. PMID 28547690. S2CID 25912204.
  17. ^ a b Anita Goswami-Giri, Neha Sawant. "Separation of polyphenol oxidase and its inhibitor from onion leaves on Lignin Column".
  18. ^ Duke SO, Vaughn KC (April 1982). "Lack of involvement of polyphenol oxidase in ortho-hydroxylation of phenolic compounds in mung bean seedlings". Physiologia Plantarum. 54 (4): 381–385. doi:10.1111/j.1399-3054.1982.tb00696.x.
  19. ^ Valero E, Garcia-Moreno M, Varon R, Garcia-Carmona F (1991). "Time-dependent inhibition of grape polyphenol oxidase by tropolone". J. Agric. Food Chem. 39 (6): 1043–1046. doi:10.1021/jf00006a007.
  20. ^ Del Signore A, Romeoa F, Giaccio M (May 1997). "Content of phenolic substances in basidiomycetes". Mycological Research. 101 (5): 552–556. doi:10.1017/S0953756296003206.
  21. ^ Wuyts N, De Waele D, Swennen R (2006). "Extraction and partial characterization of polyphenol oxidase from banana (Musa acuminata Grande naine) roots". Plant Physiology and Biochemistry. 44 (5–6): 308–14. doi:10.1016/j.plaphy.2006.06.005. PMID 16814556.
  22. ^ García-Molina F, Muñoz JL, Varón R, Rodríguez-López JN, García-Cánovas F, Tudela J (November 2007). "A review on spectrophotometric methods for measuring the monophenolase and diphenolase activities of tyrosinase". Journal of Agricultural and Food Chemistry. 55 (24): 9739–49. doi:10.1021/jf0712301. PMID 17958393.
  23. ^ Haghbeen K, Wue Tan E (January 2003). "Direct spectrophotometric assay of monooxygenase and oxidase activities of mushroom tyrosinase in the presence of synthetic and natural substrates". Analytical Biochemistry. 312 (1): 23–32. doi:10.1016/S0003-2697(02)00408-6. PMID 12479831.
  24. ^ Espín JC, Morales M, Varón R, Tudela J, García-Cánovas F (October 1995). "A continuous spectrophotometric method for determining the monophenolase and diphenolase activities of apple polyphenol oxidase". Analytical Biochemistry. 231 (1): 237–46. doi:10.1006/abio.1995.1526. PMID 8678307.
  25. ^ Rescigno A, Sollai F, Rinaldi AC, Soddu G, Sanjust E (March 1997). "Polyphenol oxidase activity staining in polyacrylamide electrophoresis gels". Journal of Biochemical and Biophysical Methods. 34 (2): 155–9. doi:10.1016/S0165-022X(96)01201-8. PMID 9178091.
  26. ^ Pomerantz SH (June 1964). "Tyrosine hydroxylation catalyzed by mammalian tyrosinase: an improved method of assay". Biochemical and Biophysical Research Communications. 16 (2): 188–94. doi:10.1016/0006-291X(64)90359-6. PMID 5871805.
  27. ^ Naish-Byfield S, Riley PA (November 1992). "Oxidation of monohydric phenol substrates by tyrosinase. An oximetric study". The Biochemical Journal. 288 (Pt 1): 63–7. doi:10.1042/bj2880063. PMC 1132080. PMID 1445282.
  28. ^ Li Y, Zafar A, Kilmartin PA, Reynisson J, Leung IK (November 2017). "Development and Application of an NMR-Based Assay for Polyphenol Oxidases". ChemistrySelect. 2 (32): 10435–41. doi:10.1002/slct.201702144.
  29. ^ a b c Ünal MÜ (2007). "Properties of polyphenol oxidase from Anamur banana (Musa cavendishii)". Food Chemistry. 100 (3): 909–913. doi:10.1016/j.foodchem.2005.10.048.
  30. ^ a b c d e f g Vámos-Vigyázó L (1981). "Polyphenol oxidase and peroxidase in fruits and vegetables". Critical Reviews in Food Science and Nutrition. 15 (1): 49–127. doi:10.1080/10408398109527312. PMID 6794984.
  31. ^ a b c d Thygesen PW, Dry IB, Robinson SP (October 1995). "Polyphenol oxidase in potato. A multigene family that exhibits differential expression patterns". Plant Physiology. 109 (2): 525–31. doi:10.1104/pp.109.2.525. PMC 157616. PMID 7480344.
  32. ^ a b Robinson SP, Loveys BR, Chacko EK (1993). "Polyphenol Oxidase Enzymes in the Sap and Skin of Mango Fruit". Functional Plant Biology. 20 (1): 99–107. doi:10.1071/pp9930099. ISSN 1445-4416.
  33. ^ Shelby T. Peres; Kelsey A. Oonk; Kasandra J. Riley (29 October 2019). "The Avocado Lab: An Inquiry-Driven Exploration of an Enzymatic Browning Reaction" (PDF). Rollins College, CourseSource. Retrieved 8 March 2020.
  34. ^ Rocha AM, Cano MP, Galeazzi MA, Morais AM (1 August 1998). "Characterisation of 'Starking' apple polyphenoloxidase". Journal of the Science of Food and Agriculture. 77 (4): 527–534. doi:10.1002/(sici)1097-0010(199808)77:4<527::aid-jsfa76>3.0.co;2-e. hdl:10261/114868. ISSN 1097-0010.
  35. ^ a b Son SM, Moon KD, Lee CY (April 2001). "Inhibitory effects of various antibrowning agents on apple slices". Food Chemistry. 73 (1): 23–30. doi:10.1016/s0308-8146(00)00274-0.
  36. ^ Nicolas JJ, Richard-Forget FC, Goupy PM, Amiot MJ, Aubert SY (1994). "Enzymatic browning reactions in apple and apple products". Critical Reviews in Food Science and Nutrition. 34 (2): 109–57. doi:10.1080/10408399409527653. PMID 8011143.
  37. ^ "Novel Food Information - Arctic Apple Events GD743 and GS784". Novel Foods Section, Food Directorate, Health Products and Food Branch, Health Canada, Ottawa. 20 March 2015. Retrieved 5 November 2016.
  38. ^ Derardja AE, Pretzler M, Kampatsikas I, Barkat M, Rompel A (September 2017). "Purification and Characterization of Latent Polyphenol Oxidase from Apricot (Prunus armeniaca L.)". Journal of Agricultural and Food Chemistry. 65 (37): 8203–8212. doi:10.1021/acs.jafc.7b03210. PMC 5609118. PMID 28812349.
  39. ^ Derardja AE, Pretzler M, Kampatsikas I, Barkat M, Rompel A (December 2019). "Inhibition of apricot polyphenol oxidase by combinations of plant proteases and ascorbic acid". Food Chemistry. 4: 100053. doi:10.1016/j.fochx.2019.100053. PMC 6804514. PMID 31650127.
  40. ^ Beck G, Habicht GS (November 1996). "Immunity and the Invertebrates" (PDF). Scientific American. 275 (5): 60–66. Bibcode:1996SciAm.275e..60B. doi:10.1038/scientificamerican1196-60. PMID 8875808.
  41. ^ Decker H, Tuczek F (August 2000). "Tyrosinase/catecholoxidase activity of hemocyanins: structural basis and molecular mechanism". Trends in Biochemical Sciences. 25 (8): 392–7. doi:10.1016/S0968-0004(00)01602-9. PMID 10916160.
  42. ^ Molitor C, Mauracher SG, Rompel A (March 2016). "Aurone synthase is a catechol oxidase with hydroxylase activity and provides insights into the mechanism of plant polyphenol oxidases". Proceedings of the National Academy of Sciences of the United States of America. 113 (13): E1806-15. Bibcode:2016PNAS..113E1806M. doi:10.1073/pnas.1523575113. PMC 4822611. PMID 26976571.
  43. ^ Molitor C, Mauracher SG, Pargan S, Mayer RL, Halbwirth H, Rompel A (September 2015). "Latent and active aurone synthase from petals of C. grandiflora: a polyphenol oxidase with unique characteristics". Planta. 242 (3): 519–37. doi:10.1007/s00425-015-2261-0. PMC 4540782. PMID 25697287.