Abstract: The activities of glutamine synthetase (GS), glutamate syn-thase (GOGAT), glutamate dehydrogenase (GDH) and alanine dehydro-genase (ADH) were detected in crude extracts of Rhodobacter sphaeroides strain 601. The GDH activity of the strain in cultures grown at low concentration of ammonia was low, but high when an excess of ammonia was present. On the other hand, GS/GOGAT activities were usually higher when the ammonia concentration was limited for growth. Addition of methionine sulphoximine (MSX), an inhibitor of GS, to strain 601 growing on ammonia or molecular nitrogen as nitrogen source resulted in cessation of growth, which did not occur when the inhibitor was added to strain 601 growing on L-glutamate. The results demonstrated that ammonia was assimilated via GS/GOGAT pathway and the GDH pathway in Rhodobaeter sphaeroides strain 601.

Key words: Ammonia assimilation, GH/GOGAT pathway, GDH path-way, Rhodobacter sphaeroidcs

摘要： 本文测定了浑球红假单胞菌(Rhodobacter sphaeroides)菌株601谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、谷氨酸脱氢酶(GDH)和丙氨酸脱氢酶(ADH)的活性。低氨时,GS/GOGAT活力高,GDH活力低,高氨时,GS/GOGAT活力低,GDH活力高。在以分子氮或低浓度氨为氮源的培养条件下,加入GS抑制刑MSX(L-methionine-DL-sulphoximine),细菌生长受到抑制。但是,生长在以谷氨酸为氮源的细菌则不受影响。上述结果表明,浑球红假单胞菌菌株601氨同化是通过GS/GOGAT途径和GDH途径。

关键词: 氨同化, GS/GOGAT途径, GDH途径, 浑球红假单胞菌