REDUCTION OF NITRATE AND NITRITE BY SUBCELLULAR PREPARATIONS OF ANABAENA CYLINDRICA II. REDUCTION OF NITRATE TO NITRITE1

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Abstract
Reduction of nitrate to nitrite by particulate preparations of Anabaena cylindrica was investigated. Preparations which showed high activity of nitrate reductase were obtained by sonication (preparation A) or acetone treatment (preparation B). The preparation A also showed a high activity of DPIP-ascorbate photooxidation. The nitrate reductase system accepted electrons from either reduced ferredoxin (preparation A & B) or NADH (preparation B), but not directly from NADPH. Ferredoxin was active when reduced either by action of photochemical system I or by NADPH and NADP-reductase, but dithionite-reduced ferredoxin was completely inactive. Ferredoxin could be replaced with methyl viologen, benzyl viologen and diquat. Reduced FMN and FAD could serve as electron donors, but the affinity of the reductase toward these flavin compounds was very low.