Cytochrome Oxidase is a Possible Photoreceptor in Mitochondria

Abstract

The effect of light on respiration of intact mouse liver mitochondria was examined at various temperatures using various interference filters. State 3 respiration, namely, O 2 consumption in the presence of ADP, was clearly activated by visible light around 600 nm (orange-red) and 420 nm. This photosensitivity was also observed for ascorbate-tetramethyl-p-phenylene-diamine (TMPD) oxidation by the intact mitochondrial preparation in the presence of antimycin A. These results clearly show that the photoreceptor of this activation is cytochrome oxidase which in the oxidized state has absorption maxima at 600 nm and 420—418 nm. Uncoupled mitochondria and purified cytochrome oxidase were not activated by white light, suggesting that only cytochrome oxidase coupled with oxidative phosphorylation has this photosensitivity. Similar findings obtained for bird brain mitochondria suggest that the photosensitivity may be a common property in higher animal mitochondria, and that mitochondria in a special part of bird brain could be a photoreceptor of some photophysiological process, relating to gonadal growth.