Catechol oxidase

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Catechol oxidase (EC 1.10.3.1; CAS number: 9002-10-2) is an enzyme that catalyses the oxidation of phenols such as catechol. Catechol oxidase is a copper-containing enzyme whose activity is similar to that of tyrosinase, a related class of copper oxidases.

Catechol oxidase carries out the oxidation of phenols such as catechol, using dioxygen (O₂). In the presence of catechol, benzoquinone is formed (see reaction below). Hydrogens removed from catechol combine with oxygen to form water.

[edit] Browning in Fruit

Fruits and vegetables can be kept fresh by storage at coldish temperatures, because the cold slows down all cellular mechanisms. This is similar to hibernation - the cells are still alive, but do not need a high turnover of oxygen and nutrients. Nevertheless, during the ripening of apples and bananas, browning occurs. The browning is caused by a reaction between catechol and oxygen, catalyzed by the enzyme "catechol oxidase," resulting in benzoquinone, a brownish compound toxic to bacteria. When the peel is damaged, oxygen can then react with the catechol, protecting the fruit. Nitrogen is sometimes used to insulate the fruit - extending shelf life by not allowing oxygen to come in contact with the fruit.

[edit] References

Solomon, E.I.; Chen, P.; Metz, M.; Lee, S.-K.; Palmer, A.E. (2001). "Oxygen Binding, Activation, and Reduction to Water by Copper Proteins". Angew. Chem. Int. Ed. 40: 4570–4590. doi:10.1002/1521-3773(20011217)40:24<4570::AID-ANIE4570>3.0.CO;2-4. PMID 12404359. .