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


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.
Pastore
D
D
Dipartimento di Scienze Animali, Vegetali e dell'Ambiente, Università del Molise, Campobasso, Italy.
Greco
M
M
Passarella
S
S
D000818:Animals; D003574:Cytochrome c Group / Q000378:metabolism; D004579:Electron Transport / Q000528:radiation effects; D003576:Electron Transport Complex IV / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D006371:Helium; D066298:In Vitro Techniques; D007700:Kinetics; D007834:Lasers; D008930:Mitochondria, Liver / Q000378:metabolism / Q000528:radiation effects; D009356:Neon; D010084:Oxidation-Reduction; D051381:Rats
D003574:Cytochrome c Group; D006371:Helium; D009356:Neon; D003576:Electron Transport Complex IV