- 作者: A. A. Saboury* and M. Alijanianzadeh
- 作者服務機構: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
- 中文摘要:
The effect of ethyl xanthate(I) and propyl xanthate(II) on the kinetics of hydroxylation by mushroom
tyrosinase (MT) has been investigated at 20°C in 10mMphosphate buffer solution, pH 6.8. 4-[(4-Methylphenyl)
azo]-phenol (MePAPh) was used as a synthetic substrate for the enzyme for cresolase reaction.
The results show that ethyl xanthate and propyl xanthate can activate or inhibit the cresolase activity of
mushroomtyrosinase depending on the concentration of these effectors. Both I and II act uncompetitive at
relatively high concentrations (20-50μM). The inhibition constant (Ki) values for I and II are 13.8 and 11
μM, respectively. However, both I and II act as activators at relatively low concentrations (0-11.5μM).
Activation of the enzyme in low concentrations of xanthates arises from increasing the affinity of binding
for the substrate as well as increasing the enzyme catalytic constant. The activation constant (Ka) values
for I and II are 1.88 and 2.68μM, respectively. The enzyme has two distinct sites for both effectors. The
first one is a high-affinity activation site and the other is a low-affinity inhibition site. - 英文摘要: --
- 中文關鍵字: Mushroom tyrosinase; Ethyl xanthate; Propyl xanthate; Uncompetitive inhibition; Activation.
- 英文關鍵字: --