Inhibition of Proteinase K Activity by Copper(II) Ions
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- 作者：Lisa A. Stone ; Graham S. Jackson ; John Collinge ; Jonathan D. F. Wadsworth ; Anthony R. Clarke
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：January 9, 2007
- 年：2007
- 卷：46
- 期：1
- 页码：245 - 252
- 全文大小：169K
- 年卷期：v.46,no.1(January 9, 2007)
- ISSN：1520-4995
文摘
Disease-related prion protein, PrPSc, can be distinguished from its normal cellular precursor,PrPC, by its detergent insolubility and partial resistance to proteolysis. Several studies have suggestedthat copper(II) ions can convert PrPC to a proteinase K-resistant conformation; however, interpretation ofthese studies is complicated by potential inhibition of proteinase K (PK) by copper(II) ions. Here wehave examined directly the kinetic and equilibrium effects of copper(II) ions on PK activity using a simplesynthetic substrate, p-nitrophenyl acetate. We show that at equilibrium two to three copper(II) ions bindstoichiometrically to PK and destroy its activity (Kd < 1 
M). This inhibition has two components, aninitial reversible and weak binding phase and a slower, irreversible abolition of activity with a half-timeof 6 min at saturating copper(II) ion concentrations. Copper(II) ions produce a similar biphasic inhibitionof PK activity in the presence of brain homogenate but only when the copper(II) ion concentration exceedsthat of the chelating components present in brain tissue. Under these conditions, the apparent resistanceof PrPC to proteolysis by PK appears to be directly attributable to the inhibition of PK activity by copper(II) ions.
M). This inhibition has two components, aninitial reversible and weak binding phase and a slower, irreversible abolition of activity with a half-timeof 6 min at saturating copper(II) ion concentrations. Copper(II) ions produce a similar biphasic inhibitionof PK activity in the presence of brain homogenate but only when the copper(II) ion concentration exceedsthat of the chelating components present in brain tissue. Under these conditions, the apparent resistanceof PrPC to proteolysis by PK appears to be directly attributable to the inhibition of PK activity by copper(II) ions.