Dincturk H B, Knaff D B
Department of Chemistry, and Biochemistry, Texas Tech University Lubbock 79409-1061, USA.
Mol Biol Rep. 2000 Sep;27(3):141-8. doi: 10.1023/a:1007107909619.
DNA coding for the ferredoxin-dependent glutamate synthase (EC 1.4.7.1) of spinach chloroplasts has been cloned and sequenced. It consists of 5015 bp and starts with the codon for the N-terminal cysteine of the mature protein. Ferredoxin-dependent glutamate synthase is one of the key enzymes in the early stages of ammonia assimilation in plants, algae and cyanobacteria. In addition to the ferredoxin-dependent enzyme, there are two other forms of glutamate synthase, one of which uses NADH as the electron donor and a second that uses NADPH. Although all three forms catalyze the reductive transamidation of the amido nitrogen from glutamine to 2-oxoglutarate to form two molecules of glutamate, ferredoxin-dependent glutamate synthases differ from the NADH and NADPH-dependent forms in subunit composition and amino acid sequence. The recent availability of sequence data for glutamate synthases from spinach and from two archael species has produced a clearer and more detailed picture of the evolution of this key enzyme in nitrogen metabolism and the origins of the two subunit/domain structure of the enzyme.
编码菠菜叶绿体中铁氧还蛋白依赖性谷氨酸合酶（EC 1.4.7.1）的DNA已被克隆并测序。它由5015个碱基对组成，起始密码子对应成熟蛋白的N端半胱氨酸。铁氧还蛋白依赖性谷氨酸合酶是植物、藻类和蓝细菌氨同化早期阶段的关键酶之一。除了铁氧还蛋白依赖性酶外，还有另外两种形式的谷氨酸合酶，其中一种以NADH作为电子供体，另一种以NADPH作为电子供体。尽管这三种形式都催化谷氨酰胺的酰胺氮向2-氧代戊二酸的还原性转氨作用，以形成两分子谷氨酸，但铁氧还蛋白依赖性谷氨酸合酶在亚基组成和氨基酸序列上与NADH和NADPH依赖性形式不同。最近获得的菠菜和两种古细菌物种的谷氨酸合酶序列数据，使人们对这种氮代谢关键酶的进化以及该酶的两个亚基/结构域结构的起源有了更清晰、更详细的了解。
