Diphosphopyridine Nucleotide-Nitrate Reductase from Soybean Nodules.

Abstract

Cell free extracts of soybean nodules have been prepared which catalyze the reduction of nitrates to nitrites in presence of reduced diphosphopyridine nucleotide. The enzyme activity is strongly inhibited by sodium azide and cupric sulfate and weakly inhibited by potassium cyanide. Initial purification procedures have resulted in a five-fold increase in specific activity. It was shown that nitrate reductase is present in all of the eleven samples of nodules tested, from 4 legume species. Results are discussed from the standpoint of the requirement of Mo for both nitrate reduction and N fixation, and it is concluded that there is ample indirect evidence to consider the possibility of a role of nitrate reductase in N fixation.