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

Abstract

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.

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

“…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)]. …”

Isolation, Cloning and Characterization of a Tyrosinase with Improved Activity in Organic Solvents from <i>Bacillus megaterium</i>

“…0.1% SDS and deteriorated greatly at levels 1 0.5% similar to the diphenolase activity. Tyrosinases from the South African clawed frog Xenopus laevis [Wittenberg and Triplett, 1985] and A. bisporus [Espin and Wichers, 1999] have been shown to be activated by detergents. Among bacterial tyrosinases, SDS activation was observed for Bacillus sp.…”

Innovative use of intact seeds of Mucuna monosperma Wight for improved yield of L-DOPA

“…It is suggested that the activation process involves a limited conformational changes such as a swelling of the protein rather than a dissociation or aggregation. 19 However, at higher concentrations, enzyme gets denatured and activity drops eventually. Thus all elicitors used in this study, lead to increase in the synthesis of L-DOPA through increased activity of tyrosinase.…”