Title: The effect of pH changes on the optical spectrum of oxidised cytochrome oxidase
Abstract: The sensitivity to pH changes of oxidised cytochrome oxidase, oxidised oxidase-cyanide and oxidase-azide complexes was investigated by optical difference spectroscopy in the pH region 6.0–8.2. The responses of the optical spectrum of oxidised oxidase and the oxidase-cyanide complex are almost fullydeveloped within some minutes aftera pH change of 1–2 units. A blue shiftof the spectrum of oxidised oxidase and the oxidase-cyanide complex is observed with decreasing pH, whereas the oxidase-azide complex is almost insensitive to the pH change. From the pH insensitivity of the oxidase-azide complex and the differences in the pH-induced spectral changes of the oxidase-cyanide complex relative to unliganded oxidase, it is concluded that the spectral pH sensitivity in the oxidised enzyme is probably associated with proton binding at ornear cytochrome a3 only. Similar absorption changes are observed with the oxidised oxidase on increasing the pH and on the binding of azide to oxidised oxidase at constant pH. It is suggested that azide binding is probably associated with the deprotonation of some ionizable group(s) in the vinicity of the cytochrome a3-CuB site.
Publication Year: 1989
Publication Date: 1989-03-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 11
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot