Nitrite reductase in Dunaliella tertiolecta: Isolation and properties

1. A soluble nitrite reductase has been isolated from cell-freepreparations of Dunaliella tertiolecta and purified fifty fold. 2. The enzyme resembles nitrite reductases isolated from higherplants in that it is a ferredoxin-nitrite reductase, but differsin that it will not accept electrons from either NADH or NADPHeven if exogenous diaphorase is added. 3. The Km value for nitrite is 1.1 x 10^–4 M and the molecularweight as determined by chromatography on G-200 Sephadex is70,000. 4. The rates of nitrite reduction obtained in vitro, using thedithionite-viologen electron donor system are sufficient toaccount for the in vivo rates of nitrate and nitrite assimilationobserved in this species. (Received July 4, 1969; )