Characterisation of Latent Polyphenol Oxidase in Table Beet: Effect of Sodium Dodecyl Sulphate

Escribano, Josefa; Cabanes, Juana; Garcıia-Carmona, Francisco

doi:10.1002/(sici)1097-0010(199701)73:1<34::aid-jsfa689>3.3.co;2-r

Cited by 10 publications

(13 citation statements)

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“…The sigmoid plot found with p-cresol as substrate was possibly due to the rate limiting monophenolase activity and the activation of the enzyme by the appearance of the diphenol product [Sánchez-Ferrer et al (1995)]. This was confirmed by the effect of SDS which removed the sigmoid shape and which has been shown to activate the enzyme from other sources [Escribano et al (1997), Espin and Wichers (1999)]. …”

Section: Discussionsupporting

confidence: 87%

Polyphenol oxidase activity in dormant saffron (Crocus sativus L.) corm

Saiedian

Keyhani

Keyhani³

2007

Acta Physiol Plant

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Crocus sativus L., cultivated since ancient times as the source of saffron, is a triploid plant that can be propagated only via its corms which undergo a period of dormancy. Understanding the processes taking place in the corm is essential to preserve the plant and improve its quality. Color and taste being of prime importance in the quality of the saffron spice, knowledge on polyphenol oxidase (PPO) activity in the plant is of particular interest given the role of the enzyme in fruit and vegetable browning during processing and during the storage of processed food. In this paper, PPO activity was investigated for the first time in extracts obtained from dormant C. sativus L. corms. PPO activity was detectable using L-DOPA, pyrogallol, catechol or p-cresol as substrate, each being oxidized to its corresponding o-quinone; no activity was detectable with L-tyrosine, tyramine or phenol as substrate. Two pH optima, respectively at 4.5 and 6.7, were observed with all substrates and a third one, at 8.5, was found with L-DOPA and p-cresol. Kinetics parameters studied at pH 6.7 indicated the highest catalytic efficiency (in units mg -1 prot mM -1 ) with pyrogallol: 150, then catechol: 39, L-DOPA: 6.4 and p-cresol: 4.6. The enzymatic activity was inhibited by 50% in the presence of 0.22, 0.35, 0.5 and 0.7 mM kojic acid with, respectively, catechol, pyrogallol, p-cresol and L-DOPA as substrate. When stained for PPO activity, non-denaturing gel electropherograms of extract revealed three distinct bands, indicating the presence of multiple isoenzymes in dormant C. sativus L. corms.

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Section: Discussionsupporting

confidence: 87%

Polyphenol oxidase activity in dormant saffron (Crocus sativus L.) corm

Saiedian

Keyhani

Keyhani³

2007

Acta Physiol Plant

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“…Mao). present in the soluble fraction in different fruits and vegetables [6][7][8][9]. Since colorless polyphenols are converted into dark brown quinones, the browning reaction impairs the texture, flavor, and nutritional values of fruits and vegetables.…”

Section: Introductionmentioning

confidence: 78%

Gel electrophoresis of polyphenol oxidase with instant identification by in situ blotting

Cheng

Huang

Pan

et al. 2007

Journal of Chromatography B

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“…The activation of latent tyrosinases by SDS has been widely and well reported (Moore and Flurkey, 1990;Nellapaian and Sugumaran, 1996;Chazarra et al, 1996;Jiménez and García-Carmona, 1996;Escribano et al, 1997). However, this activation has not been systematically studied for latent mushroom tyrosinase.…”

Section: Resultsmentioning

confidence: 99%

“…Tyrosinase activity on TBC was monitored spectrophotometrically at 400 nm by measuring the accumulation of 4-(tert-butyl)benzo-1,2-quinone (TBQ). This o-quinone was highly stable at every pH assayed and for a longer period than those used in the activity measurements (Waite, 1976;Ros et al, 1994b;Escribano et al, 1997). One unit of active form of tyrosinase was defined as the amount of the enzyme that produces 1 µmol of TBQ per minute.…”

Section: Methodsmentioning

confidence: 99%

“…The activation of latent tyrosinases from several sources by sodium dodecyl sulfate (SDS) has been well reported (Moore and Flurkey, 1990;Nellapaian and Sugumaran, 1996;Chazarra et al, 1996;Jiménez and García-Carmona, 1996;Escribano et al, 1997). It is assumed that SDS binds to the latent enzyme below its critical micellar concentration and induces conformational changes that cause the activation of the latent enzyme (Moore and Flurkey, 1990;Nellapaian and Sugumaran, 1996).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Activation of a Latent Mushroom (Agaricus bisporus) Tyrosinase Isoform by Sodium Dodecyl Sulfate (SDS). Kinetic Properties of the SDS-Activated Isoform

Espı́n¹,

Wichers²

1999

J. Agric. Food Chem.

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This study reports the activation of a latent mushroom tyrosinase isoform by sodium dodecyl sulfate (SDS). The activation process of latent mushroom tyrosinase by SDS is characterized by the presence of a lag period (tau) prior to the attainment of a steady-state rate (V(ss)). This could be related to a slow conformational change of the latent enzyme to render the active isoform. The molecular size of the latent isoform was 67 kDa as determined by SDS-PAGE and western-blotting assays. This size did not change after activation by SDS. The molecular size of the protease-activated isoform was 43 kDa. tau and V(ss) displayed a sigmoidal relationship to the concentration of SDS, but tau was not dependent on o-diphenol or enzyme concentration. Increasing SDS concentrations decreased tau, but then lower V(ss) values were detected because of a possible excess of unfolding and subsequent denaturation of the protein. The same reaction mechanism operated in both SDS-activated and protease-activated tyrosinase isoforms despite their different kinetic features. A possible mechanism for the activation of this latent tyrosinase by SDS is proposed.

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Characterisation of Latent Polyphenol Oxidase in Table Beet: Effect of Sodium Dodecyl Sulphate

Cited by 10 publications

References 0 publications

Polyphenol oxidase activity in dormant saffron (Crocus sativus L.) corm

Polyphenol oxidase activity in dormant saffron (Crocus sativus L.) corm

Gel electrophoresis of polyphenol oxidase with instant identification by in situ blotting

Activation of a Latent Mushroom (Agaricus bisporus) Tyrosinase Isoform by Sodium Dodecyl Sulfate (SDS). Kinetic Properties of the SDS-Activated Isoform

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