CARBON-DIOXIDE FIXATION BY LUPIN ROOT-NODULES .1. CHARACTERIZATION, ASSOCIATION WITH PHOSPHOENOLPYRUVATE CARBOXYLASE, AND CORRELATION WITH NITROGEN-FIXATION DURING NODULE DEVELOPMENT
CARBON-DIOXIDE FIXATION BY LUPIN ROOT-NODULES .1. CHARACTERIZATION, ASSOCIATION WITH PHOSPHOENOLPYRUVATE CARBOXYLASE, AND CORRELATION WITH NITROGEN-FIXATION DURING NODULE DEVELOPMENT
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DOI：
10.1104/pp.60.1.47
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发表时间：
1977-01-01
期刊：
影响因子：
7.4
通讯作者：
SUTTON, WD
中科院分区：
文献类型：
--
作者：
CHRISTELLER, JT;LAING, WA;SUTTON, WD
测定了不同年龄卢平根瘤体内CO2固定和体外磷酸烯醇丙酮酸（PEP）羧化酶水平。这两种活性在根瘤组织中都比在主根组织和次生根组织中都要高，并且随着N2固定的开始增加了约3倍。PEP羧化酶活性主要位于成熟根瘤的含根瘤菌区。纯化后的类细菌不含任何活性。从根瘤、根和叶中部分纯化的PEP羧化酶在许多动力学参数上是相同的。在根瘤发育过程中，体内CO2固定活性和体外PEP羧化酶活性均与根瘤乙炔还原活性显著相关。成熟根瘤体内CO2固定的最大速率为7.9 nmol h-1 mg鲜重，与N2固定速率和氨基酸易位的报道值相似。结果表明，草酰乙酸作为氨同化和氨基酸合成的主要钙骨架受体是通过PEP羧化酶反应而不是通过三羧酸循环提供的。PEP的来源可能是糖酵解；二氧化碳的主要来源大概是呼吸作用。
In vivo CO2 fixation and in vitro phosphoenolpyruvate (PEP) carboxylase levels were measured in lupin (Lupinus angustifolius L.) root nodules of various ages. Both activities were greater in nodule tissue than in either primary or secondary root tissue, and increased about 3-fold with the onset of N2 fixation. PEP carboxylase activity was predominantly located in the bacteroid[Rhizobium]-containing zone of mature nodules. Purified bacteroids contained no activity. Partially purified PEP carboxylases from nodules, roots and leaves were identical in a number of kinetic parameters. Both in vivo CO2 fixation activity and in vitro PEP carboxylase activity were significantly correlated with nodule acetylene reduction activity during nodule development. The maximum rate of in vivo CO2 fixation in mature nodules was 7.9 nmol h-1 mg fresh weight-1, similar to rates of N2 fixation and reported values for amino acid translocation. The results suggest that the oxaloacetate used as the primary Ca skeleton acceptor for ammonia assimilation and amino acid synthesis in lupin nodules is provided via the PEP carboxylase reaction rather than through the tricarboxylic acid cycle. The source of PEP is presumably glycolysis; the major source of CO2 is presumably respiration.