pH-Dependence of The Maximal Velocity of Cytochrome c Oxidase: Relation to Proton Translocation and Respiratory Control

1987 ◽  
pp. 301-309 ◽  
Author(s):  
Linda C. Gregory ◽  
Shelagh Ferguson-Miller
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Ph Dependence ◽  
Proton Translocation ◽  
Respiratory Control ◽  
Maximal Velocity

Dibucaine interacts differently with membrane and protein in cytochrome c oxidase systems

1993 ◽  
Vol 71 (1-2) ◽  
pp. 14-21
Author(s):  
Jia He ◽  
Peter Nicholls
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Proton Translocation ◽  
Tight Binding ◽  
Respiratory Control ◽  
Soret Band ◽  
Red Shift ◽  
Ph Gradients ◽  
Low Concentrations ◽  
Low Ionic Strength

Dibucaine acts as a weak protonophore in cytochrome c oxidase proteoliposomes. At low concentrations in the presence of permeant anions, it stimulates turnover and collapses enzyme-generated pH gradients. At higher concentrations, dibucaine inhibits activity of cytochrome c oxidase in proteoliposomes and the isolated enzyme. It also induces a red shift in the resting spectrum, indicating a change at the binuclear centre. This spectroscopic effect is kinetically biphasic. Dibucaine inhibits steady-state oxidase activity, but not the rate of the red shift in the cytochrome a3 Soret band during turnover. It reacts faster with the partially reduced state than with resting enzyme. The inhibition is kinetically biphasic with a noncompetitive Ki ≈ 0.5 mM. Excess dibucaine effects a maximal turnover decline of 80%. At low ionic strength only the total Vmax is affected; tight binding of cytochrome c and turnover at the "tight" site are unaffected. Dibucaine may bind to an anionic site in a hydrophobic pocket, modifying electron transfer from cytochrome a and CuA to cytochrome a3 - CuB and the oxidized spectrum of the latter centre. Stimulation of turnover in cytochrome c oxidase in proteoliposomes is due to a separate membrane-dependent proton translocation catalysed by dibucaine in the presence of permeant anions.Key words: dibucaine, cytochrome c oxidase, proteoliposomes, respiratory control, inhibition.

Sign in / Sign up

Export Citation Format

Share Document