Melanoproteins I. reactions between enzyme-generated quinones and amino acids

Mason, Howard S.; Peterson, Etta

doi:10.1016/0304-4165(65)90479-4

Cited by 182 publications

(104 citation statements)

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“…The assay employed is based on Mason and Peterson's method [29] adapted to a 96-well plate: 70 mL of 0.1M phosphate buffer pH 6.8 (PBS), 30 mL of mushroom tyrosinase diluted in phosphate buffer (167 units/mL) and various concentration of different test samples dissolved in 20 mL dimethyl sulfoxide (DMSO) were inserted into 96-well plates for 5 min pre-incubation at 308C. 100 mL L-DOPA was added to start the enzymatic reaction.…”

Section: Tyrosinase Assaymentioning

confidence: 99%

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

Zhang

Lü

Lin

et al. 2007

Journal of Enzyme Inhibition and Medicinal Chemistry

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The inhibitory effects of nobiletin and hesperidin from citrus peel crude extracts on tyrosinase diphenolase activity are evaluated. IC 50 of nobiletin and hesperidin is 1.49 mM and 16.08 mM, respectively and their inhibition mechanism is competitive type with K i ¼ 2.82 mM and noncompetitive with K i ¼ 9.16 mM, respectively. Crude extracts from citrus peel (C. unshiu Marc.) were extracted with 95% ethanol and fractionated by petroleum ether (PCPE). The ethanol phase (ECPE) was further desorbed from macroporous adsorption resin (FGRE). Their IC 50 values were 8.09 mg/mL, 7.53 mg/mL and 4.80 mg/mL, respectively. Their inhibition on melanogenesis in B16 mouse melanoma cells was also evaluated. FGRE showed a significant inhibition (42.5% at 31.25 mg/mL, p , 0.01) while hesperidin showed almost no inhibition. Nobiletin and PCPE give efficacious antiproliferation effects on B16 mouse melanoma cell with IC 50 values 88.6 mM and 62.96 mg/mL, respectively, by the MTT test. Hesperidin and other crude extracts showed very low cytotoxity to the B16 cell.

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Section: Tyrosinase Assaymentioning

confidence: 99%

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

Zhang

Lü

Lin

et al. 2007

Journal of Enzyme Inhibition and Medicinal Chemistry

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“…A generalized reaction scheme for diphenol oxidases is given in Figure 1, where it may be seen that mono-and di-hydroxy phenolics are oxidized to the corresponding quinones with the concomitant reduction of molecular 02. These quinones are highly reactive and will polymerize, either with themselves, or with amino acids or proteins, to yield a complex, heterogeneous high molecular weight structure generally called 'melanin' or Inelanoidin'; this is usually brown but can also be red, black, blue or various combinations of these (Mason and Peterson, 1965;Pierpont, 1969;Walker, 1975;Walker, 1995;Walker and Ferrar, 1996).…”

Section: Introductionmentioning

confidence: 99%

Diphenol Oxidases, Enzyme-catalysed Browning and Plant Disease Resistance

Walker

Ferrar

1998

Biotechnology and Genetic Engineering Reviews

156

120

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“…o-Benzoquinone, as well as other o-quinones produced from the oxidation of catechol, is highly reactive. Not only can it react with other molecules of catechol (3), but it also reacts with amino acids, peptides, and proteins (10,12,13). Loomis and Battaile (9) pointed out that phenols can combine with proteins reversibly by hydrogen bonding, but after oxidation they combine with proteins irreversibly via covalent condensation.…”

Section: Introductionmentioning

confidence: 99%

Effect of Phloroglucinol and Resorcinol on the Clingstone Peach Polyphenol Oxidase-catalyzed Oxidation of 4-Methylcatechol

1971

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Phloroglucinol and resorcinol are not substrates for clingstone peach (Prunus persica) polyphenol oxidase, but they react with 4-methyl-o-quinone, produced either enzymatically or nonenzymatically, to give an intense red or red-brown color with a maximal absorption at about 470 nanometers. Several colored products were isolated from an ethyl acetate extract of the reaction by two-dimensional thin layer chromatography. Based on thin layer chromatographic and spectral studies of the enzymatic and nonenzymatic reactions, polyphenol oxidase does not play a role in the reaction between 4-methyl-o-quinone and phloroglucinol, resorcinol, d-catechin, or orcinol. In such reactions, the function of polyphenol oxidase is the formation of 4-methyl-o-quinone which then reacts nonenzymatically with the above phenols. Activation energies of both enzymatic and nonenzymatic reactions were determined. o-Benzoquinone, as well as other o-quinones produced from the oxidation of catechol, is highly reactive. Not only can it react with other molecules of catechol (3), but it also reacts with amino acids, peptides, and proteins (10,12,13). Loomis and Battaile (9) pointed out that phenols can combine with proteins reversibly by hydrogen bonding, but after oxidation they combine with proteins irreversibly via covalent condensation.Phenolic compounds such as phloroglucinol and resorcinol are inhibitors of some polyphenol oxidases. For example, both phloroglucinol and resorcinol are competitive inhibitors of potato PPO3 (16), and phloroglucinol is a competitive inhibitor of peach PPO (14). On the other hand, Shannon and Pratt (17) reported that addition of phloroglucinol or resorcinol increased the rate of browning in the apple PPO-catalyzed oxidation of chlorogenic acid.Although free phloroglucinol and resorcinol are not abundant in plants, their derivatives such as the flavonoid compounds are distributed widely in plants. Using In the absence of other phenolics, the effect of 4-methylcatechol concentration on enzyme activity was studied at 420 nm. 4-Methylcatechol concentrations were varied from 9.3 X 10' to 55.8 X 10-M. The Michaelis constant was determined by the method of Lineweaver and Burk (8).Absorption Spectral Studies. The following reaction mixtures were prepared and incubated at 30 C: (I) for the enzymatic reaction: (a) 4.6 ml of 1 x I0-' M 4-methylcatechol plus 0. phloroglucinol. Spectra of each reaction were taken after 10 min, 2 hr, and 2 days. All reagents were prepared in 0.1 M citrate-0.2 M phosphate buffer, pH 6.8.Chemically synthesized 4-methyl-o-quinone was prepared according to Cason (1) and recrystallized twice from benzene. The product was kept in a brown bottle and stored in a freezer for better stability.Thin Layer Chromatography. For the enzymatic reaction, phloroglucinol at a final concentration of 8.2 X 10-' M was prepared in 5 ml of 0.1 M citrate-0.2 M phosphate buffer at pH 6.8. The compound was allowed to react with an equimolar amount of 4-methylcatechol (contained in 2 ml of the same buffer solut...

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Melanoproteins I. reactions between enzyme-generated quinones and amino acids

Cited by 182 publications

References 13 publications

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

Diphenol Oxidases, Enzyme-catalysed Browning and Plant Disease Resistance

Effect of Phloroglucinol and Resorcinol on the Clingstone Peach Polyphenol Oxidase-catalyzed Oxidation of 4-Methylcatechol

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