PHOTOSYNTHETIC NITRITE REDUCTASE FROM SPINACH1

Abstract

Photosynthetic nitrite reductase (PNiR) was purified extensively from spinach leaves by the method including acetone precipitation, ammonium sulfate fractionations and DEAE-cellulose column chromatography. The purified PNiR had the highest specific activity thus far obtained. Absorption spectrum of the purified PNiR indicated that it had no flavin component. There was no difference in the rate of photosynthetic nitrite reduction between aerobic and anaerobic conditions. In chloroplasts two reductase systems related with ferredoxin had been recognized, which were ferredoxin-nitrite and ferredoxin-NADP reductase system. The relationship between the two systems was investigated by using the reconstituted enzyme system. When the reduction of NADP was taking place, the reduction of nitrite was strongly inhibited. Some physiological significance of the phenomenon was discussed.