Cytochromes c 550 and c 552 as electron donors for nitrate and nitrite reductases in membrane fractions of rhizobium japonicum cc 705
Ranaweera, S.S.; Nicholas, D.J.D.
Biochemistry International 10(3): 415-424
Cells grown with nitrate under semi-anaerobic conditions (1% vol/vol O2, 99% N2) had increased yields, cytochromes c550 and c552 contents and nitrate and nitrite reductase activities, in membrane fractions, compared with those grown without nitrate. Cytochromes c550, c552 and c554 purified from the R. japonicum were tested as electron donors for nitrate and nitrite reductases in membrane fractions. Reduced cytochrome c550 served as an immediate reductant for nitrate and nitrite reductases; reduced cytochrome c552 exhibited a lag period and was less effective for these enzymes, whereas cytochrome c554 was ineffective. Cytochrome c550 is probably closer to the nitrate and nitrite reductase sites in the respiratory chain than is cytochrome c552.