Specific helium-neon laser sensitivity of the purified cytochrome c oxidase

Int J Radiat Biol. 2000 Jun;76(6):863-70. doi: 10.1080/09553000050029020.


Purpose: In order to gain some insight into the mechanism of interaction between Helium-Neon (He-Ne) laser light and mitochondrial cytochromes, the sensitivity of cytochrome electron transfer activity to He-Ne laser was tested.

Materials and methods: Irradiation of solutions containing either purified cytochromes or dissolved rat liver mitochondria was carried out (wavelength 632.8 nm, fluence rate 10 mW cm(-2), fluence 2 J cm(-2)); the irradiation conditions were the ones able to affect cytochrome c oxidase (COX) activity in mitochondria (Pastore et al., 1994).

Results: Cytochrome c oxidation catalysed by COX was affected by He-Ne laser irradiation of the purified enzyme. This result was obtained from measurements of the pseudo-first-order kinetic constant and from determinations of the turnover number of the enzyme, performed at different cytochrome c/COX ratios. Consistently, the kinetic parameters of COX changed. On the contrary, no alteration in the rate of electron transfer catalysed by either cytochrome c or bc1 complex was found.

Conclusions: This study shows that purified COX is a specific target of He-Ne laser light; therefore, COX may be considered to be a mitochondrial photo-acceptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytochrome c Group / metabolism
  • Electron Transport / radiation effects
  • Electron Transport Complex IV / isolation & purification
  • Electron Transport Complex IV / metabolism
  • Electron Transport Complex IV / radiation effects*
  • Helium
  • In Vitro Techniques
  • Kinetics
  • Lasers*
  • Mitochondria, Liver / metabolism
  • Mitochondria, Liver / radiation effects
  • Neon
  • Oxidation-Reduction
  • Rats


  • Cytochrome c Group
  • Helium
  • Neon
  • Electron Transport Complex IV