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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 5
BKCSDE 32(5)
May 20, 2011 

 
Title
Non-Essential Activation of Co2+ and Zn2+ on Mushroom Tyrosinase: Kinetic and Structural Stability
Author
N. Gheibi*, A. A. Saboury, M. Sarreshtehdari
Keywords
Mushroom tyrosinase, Non-essential activation, Co2+, Zn2+, pH
Abstract
Tyrosinase is a widespread enzyme with great promising capabilities. The Lineweaver-Burk plots of the catecholase reactions showed that the kinetics of mushroom tyrosinase (MT), activated by Co2+ and Zn2+ at different pHs (6, 7, 8 and 9) obeyed the non-essential activation mode. The binding of metal ions to the enzyme increases the maximum velocity of the enzyme due to an increase in the enzyme catalytic constant (kcat). From the kinetic analysis, dissociation constants of the activator from the enzyme-metal ion complex (Ka) were obtained as 5 × 104 M−1 and 8.33 × 103 M−1 for Co2+ and Zn2+ at pH 9 and 6 respectively. The structural analysis of MT through circular dichroism (CD) and intensive fluorescence spectra revealed that the conformational stability of the enzyme in these pHs reaches its maximum value in the presence of each of the two metal ions.
Page
1500 - 1506
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