Tyrosinase inactivation in its action on dopa

Muñoz‐Muñoz, José Luis; Acosta‐Motos, José Ramón; García‐Molina, Francisco; Varón, R.; Garcı́a-Ruiz, Pedro Antonio; Tudela, José; Garcı́a-Cánovas, Francisco; Rodríguez-López, JoséNeptuno

doi:10.1016/j.bbapap.2010.02.015

Cited by 34 publications

(25 citation statements)

References 45 publications

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“…Both PPO and POD are active enzymes in the production of pigments in damaged plant tissues (Albrecht and Kohlenbach, 1990). PPO is a copper protein that uses molecular oxygen to catalyze the oxidation of monophenols to o-diphenols and further to o-quinones (Muñoz-Muñoz et al, 2010); POD mediates the oxidation of L-DOPA to form dopaquinone and melanin (Nishihara et al, 2004). By evaluating the response of seed germination of different plant species to the allelochemical, L-DOPA, Nishihara et al (2004) confirmed a relationship between the changes of color on filter paper and the inhibition of radical growth.…”

Section: Discussionmentioning

confidence: 99%

The Allelochemical L-DOPA Increases Melanin Production and Reduces Reactive Oxygen Species in Soybean Roots

et al. 2011

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The non-protein amino acid, L-3,4-dihydroxyphenylalanine (L-DOPA), is the main allelochemical released from the roots of velvetbean and affects seed germination and root growth of several plant species. In the work presented here, we evaluated, in soybean roots, the effects of L-DOPA on the following: polyphenol oxidase (PPO), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities; superoxide anion (O·-2), hydrogen peroxide (H(2)O(2)), and melanin contents; and lipid peroxidation. To this end, 3-day-old seedlings were cultivated in half-strength Hoagland's solution (pH 6.0), with or without 0.1 to 1.0 mM L-DOPA in a growth chamber (at 25°C, with a light/dark photoperiod of 12/12 hr and a photon flux density of 280 μmol m(-2) s(-1)) for 24 hr. The results showed that L-DOPA increased the PPO activity and, further, the melanin content. The activities of SOD and POD increased, but CAT activity decreased after the chemical exposure. The contents of reactive oxygen species (ROS), such as O·-2 and H(2)O(2), and the levels of lipid peroxidation significantly decreased under all concentrations of L-DOPA tested. These results suggest that L-DOPA was absorbed by the soybean roots and metabolized to melanin. It was concluded that the reduction in the O·-2 and H(2)O(2) contents and lipid peroxidation in soybean roots was due to the enhanced SOD and POD activities and thus a possible antioxidant role of L-DOPA.

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Section: Discussionmentioning

confidence: 99%

The Allelochemical L-DOPA Increases Melanin Production and Reduces Reactive Oxygen Species in Soybean Roots

et al. 2011

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“…Deoxy tyrosinase oxidizes phenols and catechols to o ‐quinones, by different oxidative mechanisms. Catechol oxidation by a phenolic oxidative mechanism, results in reduction of copper to Cu 0 and tyrosinase deactivation (suicide inactivation) …”

Section: Catalytic Mechanismmentioning

confidence: 99%

Structure–function correlations in tyrosinases

2015

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Tyrosinases are metalloenzymes belonging to the type-3 copper protein family which contain two copper ions in the active site. They are found in various prokaryotes as well as in plants, fungi, arthropods, and mammals and are responsible for pigmentation, wound healing, radiation protection, and primary immune response. Tyrosinases perform two sequential enzymatic reactions: hydroxylation of monophenols and oxidation of diphenols to form quinones which polymerize spontaneously to melanin. Two other members of this family are catechol oxidases, which are prevalent mainly in plants and perform only the second oxidation step, and hemocyanins, which lack enzymatic activity and are oxygen carriers. In the last decade, several structures of plant and bacterial tyrosinases were determined, some with substrates or inhibitors, highlighting features and residues which are important for copper uptake and catalysis. This review summarizes the updated information on structure-function correlations in tyrosinases along with comparison to other type-3 copper proteins.

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“…5B) imply that this inactivation is mostly irreversible. Tyrosinase is known to be inactivated during the oxidation of DOPA 17,18) and several phenolic substrates. [19][20][21] This type of inactivation is called suicide inactivation, whose mechanism has been discussed for many years.…”

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confidence: 99%

“…Although DOPA may act as the suicide substrate in the present phenomenon, its effective concentration (around 100 mM) is considerably low as compared to those (0.25-10 mM) used for suicide inactivation under aerobic conditions. 17,18) The effectiveness of DOPA at such a low concentration implies a possibility that 2 enhances the suicide inactivation by DOPA, for instance, through conformational change of the enzyme protein by binding. However, this mechanism does not explain the fact that there was the optimum concentration for DOPA in the combination effect with 2 (Fig.…”

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confidence: 99%

“…[19][20][21] This type of inactivation is called suicide inactivation, whose mechanism has been discussed for many years. [17][18][19][20][21][22][23] For example, a two-electron transfer from the substrate to the active center Cu 2ϩ ion leading to its liberation as a Cu 0 atom was proposed as the mechanism for inactivation of tyrosinase in the enzymatic oxidation of resorcinol. 21) Compound 2 has a resorcinol moiety, but this is probably not the cause of the present inactivation, since another resorcinol derivative 3 did not suppress the melanin formation (Fig.…”

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confidence: 99%

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