Cytochrome Oxidase Activity in Cell-free Preparations from Blue-Green Algae.

The chlorophyll-containing lamellar structures isolated from Anabaena variabilis have the ability to oxidize reduced mammalian cytochrome c in the dark. This activity is oxygen dependent and heat labile. As with other cytochrome oxidase preparations, activity is stimulated by detergents and is sensitive to the ionic strength of the assay solution. The cytochrome oxidase activity is not inhibited by azide, is slightly inhibited by carbon monoxide, but is readily inhibited by potassium cyanide. This sensitivity to inhibition by cyanide distinguishes the cytochrome oxidase from cytochrome photo-oxidase which is cyanide insensitive (6). There are several studies indicating the feeble respiratory activity of blue-green algae (2-5, 9, 16, 20, 21). Cell-free preparations from blue-green algae have been found to catalyze respiratory chain oxidations (3, 4, 8, 12, 20). Whereas reduced cytochrome c photooxidation is regularly observed on illumination of particulate preparations from blue-green algae (7, 14), a "dark" cytochrome oxidase such as would participate in a respiratory chain has not revealed itself to all experimenters. Biggins (4) reported cytochrome oxidase in preparations of Anacystis nidulans and Phormidium luridlim; yet Horton (8) could not observe cytochrome oxidase activity in preparations from Anabaena variabilis, A. nidulans or Leucothrix which were active in NADH oxidation. Using "colorless" species of blue-green algae Webster and Hackett found, as did Horton, that particulate preparations exhibited NADH oxidase but not cytochrome oxidase (20). This paper reports experiments which describe a cytochrome oxidase activity in particulate preparations from A. variabilis.