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

• Published in: Journal of agricultural and food chemistry 1999-09, Vol.47 (9), p.3518-3525
• Main Authors: Espín, Juan Carlos, Wichers, Harry J
• Format: Article
• Language: English
• Subjects: Agaricales - enzymology; Agaricus - enzymology; Agrotechnological Research Institute; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Enzyme Activation; Enzymes and enzyme inhibitors; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Instituut voor Agrotechnologisch Onderzoek; Isoenzymes - metabolism; Kinetics; Monophenol Monooxygenase - metabolism; Oxidoreductases; Sodium Dodecyl Sulfate - pharmacology
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf981275p

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 (τ) 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. τ and V ss displayed a sigmoidal relationship to the concentration of SDS, but τ was not dependent on o-diphenol or enzyme concentration. Increasing SDS concentrations decreased τ, 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. Keywords: Agaricus; kinetics; latent; mushroom; SDS; tyrosinase.