Peroxide interaction with pulsed cytochrome oxidase. Optical and EPR studies

Area of Science:

• Biochemistry
• Biophysics

Background:

• Cytochrome oxidase is a crucial enzyme in cellular respiration.
• Understanding its various forms and intermediates is key to elucidating its mechanism.

Purpose of the Study:

• To characterize the 420 nm form of cytochrome oxidase using EPR and optical spectroscopy.
• To investigate the reaction of the 420 nm form with hydrogen peroxide and identify reaction products.

Main Methods:

• Electron Paramagnetic Resonance (EPR) spectroscopy.
• UV-Visible optical spectroscopy.
• Analysis of spectral properties (absorption bands, EPR signals).

Main Results:

• The 420 nm form of cytochrome oxidase exhibits a 605 nm band, g=5 EPR signals, and a blue-shifted 655 nm band.
• Reaction with hydrogen peroxide forms a peroxide complex (427 nm Soret band), a 580 nm band, and abolishes the 655 nm band and g=5 EPR signal.
• Different oxidase forms can be identified as the 420 nm or 427 nm forms.

Conclusions:

• The study identifies a peroxy intermediate during cytochrome oxidase turnover.
• Spectral characteristics allow differentiation between various cytochrome oxidase forms.
• This work contributes to understanding the catalytic cycle of cytochrome oxidase.