VANADIUM EFFECT IN NITROGEN FIXATION BY AZOTOBACTER
VANADIUM EFFECT IN NITROGEN FIXATION BY AZOTOBACTER
复制标题
DOI：
10.1016/0304-4165(72)90113-4
复制
发表时间：
1972-01-01
期刊：
影响因子：
--
通讯作者：
MCKENNA, CE
中科院分区：
文献类型：
--
作者：
BENEMANN, JR;KAMEN, MD;MCKENNA, CE
In some strains of Azotobacter vanadium will substitute for the Mo requirement of N2-fixing cell cultures. This V effect was studied using two strains of Azotobacter:A. vinelandiiOP andA. chroococcumATCC 480. Growth rate determinations showed that V could be about 50% as effective as Mo in stimulating growth on N2. However, determination of nitrogenase activity in actively growing cultures indicated that the V effect produces only about 10% of the activity of Mo-grown cells. The specific activity, and stability toward storage, air, and heat, of the nitrogenase in cell-free extracts of V-grown Azotobacter cultures were intermediate between those of Mo-grown and Mo-starved cell-free extracts.Purification of V-nitrogenase revealed V to be incorporated into the nitrogenase enzyme as part of a Mo-Fe like type protein which contained V and Mo. On the basis of the activity to Mo ratios in extracts from Mo-limited cultures we conclude that the Mo contained in V-nitrogenase substantially accounts for its observed activity.We propose that the V effect is due to V incorporation into the nitrogenase complex with consequent stabilization of the enzyme and more effective utilization of the small amount of Mo found in Mo-starved cells.
