在莱茵衣藻中鉴定一种光依赖性谷氨酸合酶活性。

Characterization of a light-dependent glutamate synthase activity in Chlamydomonas reinhardtii.

机构信息

Departamento de Bioquímica, Facultad de Química, Apartado 553, 41080, Sevilla, Spain.

出版信息

Photosynth Res. 1987 Jan;12(1):73-81. doi: 10.1007/BF00019152.

DOI:10.1007/BF00019152

Abstract

Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (Km=2.1 mM) and L-glutamine (Km=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (Km=1 mM) and L-glutamine (Km=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.

摘要

从衣藻中制备的具有光合作用活性的囊泡保留了一种光依赖性谷氨酸合酶活性，该酶对 2-氧代戊二酸（Km=2.1mM）和 L-谷氨酰胺（Km=0.9mM）具有高度特异性，分别作为酰胺基供体和受体。该活性被叠氮丝氨酸、对羟基汞苯甲酸和 3-（对氯苯基）-1,1-二甲基脲抑制。通过将衣藻光合颗粒与纯化的铁氧还蛋白-谷氨酸合酶偶联，使用抗坏血酸和 2,6-二氯苯酚靛酚作为电子供体，也可以获得光依赖性谷氨酸的合成。该系统对 2-氧代戊二酸（Km=1mM）和 L-谷氨酰胺（Km=0.8mM）作为底物也具有特异性，并受二硫苏糖醇刺激。叠氮丝氨酸和对羟基汞苯甲酸，但不是 3-（对氯苯基）-1,1-二甲基脲，抑制了重组活性；高浓度的 2-氧代戊二酸具有抑制作用。