Some photoreactions of isolated cytochrome b-559

Cytochrome b-559 was isolated from spinach and the alga Bumilleriopsis filiformis (Xanthophyceae) and characterized by functional properties: (a) It was active as electron acceptor in a diaphorase system using NADPH as donor and ferredoxin and ferredoxin-NADP reductase as redox proteins. (b) It exhibited photooxidation with Photosystem-I particles, when illuminated with 707 nm light. (c) It was photooxidized by Photosystem-II particles and 652 nm light at room temperature. Light greater than 702 nm was ineffective. The data corroborate previous reports on redox reactions of bound cytochrome b-559.