AMMONIA ASSIMILATION BY RHIZOBIUM CULTURES AND BACTEROIDS
AMMONIA ASSIMILATION BY RHIZOBIUM CULTURES AND BACTEROIDS
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DOI：
10.1099/00221287-86-1-39
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发表时间：
1975-01-01
期刊：
影响因子：
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通讯作者：
DILWORTH, MJ
中科院分区：
文献类型：
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作者：
BROWN, CM;DILWORTH, MJ
根瘤菌自由生活培养物同化氨的酶。是谷氨酰胺合成酶（EC. 6.3.1.2）、谷氨酸合酶（L-谷氨酰胺：2-酮戊二酸氨基转移酶）和谷氨酸脱氢酶（EC 1.4.1.4）。在恒化器中限制氨或硝酸盐的条件下，研究了红球藻对氨的同化作用。豆豆属R.三叶草河japonicum通过谷氨酰胺合成酶和谷氨酸合成酶进行。在葡萄糖限制和无机氮过量的情况下，氨通过谷氨酸脱氢酶同化，提取物中既没有谷氨酰胺合成酶也没有谷氨酸合成酶活性。谷氨酸合酶的辅酶特异性因物种而异，对于快速生长的R.豆豆属R.梅利托蒂河菜豆河生长缓慢的R.日本山核桃测定了大豆、蚕豆、豌豆、羽扇豆、紫花苜蓿、红小豆和菜豆根瘤菌的谷氨酰胺合成酶、谷氨酸合成酶和谷氨酸脱氢酶的活性。结节所有类杆菌制剂，除来自mM的制剂外。sativa和P. coccineus含有谷氨酸合成酶，但只有大豆和羽扇豆有明显的活性。类杆菌的谷氨酰胺合成酶活性较低，但在所有根瘤培养上清中均表现出较高的活性。谷氨酸脱氢酶活性存在于所有检查的类菌体样品中。没有证据表明谷氨酰胺合成酶/谷氨酸合成酶系统在根瘤氨同化中发挥作用，这表明类杆菌中固氮产生的氨被植物系统的酶同化。
The enzymes involved in the assimilation of ammonia by free-living cultures ofRhizobiumspp. are glutamine synthetase (EC. 6.3.1.2), glutamate synthase (l-glutamine: 2-oxoglutarate amino transferase) and glutamate dehydrogenase (EC 1.4.1.4). Under conditions of ammonia or nitrate limitation in a chemostat the assimilation of ammonia by cultures ofR. leguminosarum, R. trifoliiandR. japonicumproceeded via glutamine synthetase and glutamate synthase. Under glucose limitation and with an excess of inorganic nitrogen, ammonia was assimilated via glutamate dehydrogenase, neither glutamine synthetase nor glutamate synthase activities being detected in extracts. The coenzyme specificity of glutamate synthase varied according to species, being linked to NADP for the fast-growingR. leguminosarum, R. melitoti, R. phaseoliandR. trifoliibut to NAD for the slow-growingR. japonicumandR. lupini.Glutamine synthetase, glutamate synthase and glutamate dehydrogenase activities were assayed in sonicated bacteroid preparations and in the nodule supernatants ofGlycine max, Vicia faba, Pisum sativum, Lupinus luteus, Medicago sativa, Phaseolus coccineusandP. vulgarisnodules. All bacteroid preparations, except those fromM. sativaandP. coccineus, contained glutamate synthase but substantial activities were found only inGlycine maxandLupinus luteus. The glutamine synthetase activities of bacteroids were low, although high activities were found in all the nodule supernatants. Glutamate dehydrogenase activity was present in all bacteroid samples examined. There was no evidence for the operation of the glutamine synthetase/glutamate synthase system in ammonia assimilation in root nodules, suggesting that ammonia produced by nitrogen fixation in the bacteroid is assimilated by enzymes of the plant system.