DOES LIGHT-INDUCED RELIEF OF CYTOCHROME-C-OXIDASE FROM CO-INDUCED INHIBITION RESULT IN PHOTO-REACTIVATION OF CO-INHIBITED RESPIRATION IN SPERM OF SEA-URCHIN, OYSTER AND FISH

Light irradiation, at a light fluence rate sufficient for the strong p hoto-reactivation of the CO-inhibited cytochrome c oxidase in mitochon dria isolated from the sperm of fish, oyster and sea urchin, weakly ac tivated the CO-inhibited respiration only in the sea urchin sperm, wit h peaks of photo-reactivation corresponding to those in the absorption spectrum of CO-bound cytochrome aa(3). NADH cytochrome c reductase wa s inhibited by CO, weakly in mitochondria from sea urchin sperm and co mpletely in those from fish and oyster sperm. The CO-induced complete inhibition of cytochrome c reduction in fish and oyster sperm probably does not allow the photo-reactivation of CO-inhibited cytochrome c ox idase to augment CO-blocked respiration. At a light fluence rate highe r than that mentioned above, photo-activation of NADH cytochrome c red uctase, found in the sperm of oyster and sea urchin, occurred even in the presence of CO in mitochondria isolated from sea urchin sperm and strongly activated CO-inhibited respiration in sea urchin sperm, with peaks corresponding to those in the absorption spectrum of reduced cyt ochrome b. The acceleration of cytochrome c reduction due to the photo -activation of this complex enzyme in sea urchin sperm probably induce s another activation of CO-inhibited respiration at the high light flu ence rate.