The evolution of glutamate synthase.
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.
Dincturk
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Department of Chemistry, and Biochemistry, Texas Tech University Lubbock 79409-1061, USA. dincturk@itu.edu.tr
Knaff
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D000594:Amino Acid Oxidoreductases / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D005970:Glutamate Synthase / Q000235:genetics*; D008969:Molecular Sequence Data; D009249:NADP / Q000737:chemistry; D010940:Plant Proteins / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D018724:Spinacia oleracea / Q000201:enzymology; D013379:Substrate Specificity
D001426:Bacterial Proteins; D010940:Plant Proteins; D009249:NADP; D000594:Amino Acid Oxidoreductases; D005970:Glutamate Synthase; C042233:glutamate synthase (ferredoxin)