Purification and properties of soluble cytochrome b-560 from spinach leaves

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A b-type cytochrome having an α-band at 560 nm was isolated from spinach leaves (Spinacia oleracea). A method is described for preparing this cytochrome, cytochrome b-560 (spinach), in a purified state. The cytochrome has, in its reduced state, absorption bands at 560 nm (α), 530 nm (β) and 427 nm (γ) ; and in the oxidized state at 562 nm (α), 529 nm (β) and 417 nm (γ). The pyridine ferro-haemochrome prepared from cytochrome b-560 had an α-band at 556.5 nm, indicating the protohaem-nature of the prosthetic group. The cytochrome has an oxidation-reduction potential (E'_0) of+0.13V at pH 7.0, as measured using the ferri-ferro oxalate system. The cytochrome is rapidly reduced on illumination with red or far-red light in the presence of spinach chloroplasts and is oxidized at a slower rate in the dark. This photoreduction is inhibited by 1 × 10^<-6>M 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The molecular weight of the cytochrome is 30,000 as estimated by the dextran gel filtration method.
日本植物生理学会の論文