Premium
Nitrogen‐assimilating enzymes in land plants and algae: phylogenic and physiological perspectives
Author(s) -
Inokuchi Ritsuko,
Kuma Keiichi,
Miyata Takashi,
Okada Mitsumasa
Publication year - 2002
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2002.1160101.x
Subject(s) - glutamate synthase , glutamine synthetase , nitrogen assimilation , biochemistry , glutamate dehydrogenase , nitrite reductase , asparagine synthetase , nitrate reductase , phosphoenolpyruvate carboxylase , biology , enzyme , ammonium , asparagine , glutamine , autotroph , nitrogen cycle , chemistry , nitrogen , glutamate receptor , amino acid , receptor , genetics , organic chemistry , bacteria
An important biochemical feature of autotrophs, land plants and algae, is their incorporation of inorganic nitrogen, nitrate and ammonium, into the carbon skeleton. Nitrate and ammonium are converted into glutamine and glutamate to produce organic nitrogen compounds, for example proteins and nucleic acids. Ammonium is not only a preferred nitrogen source but also a key metabolite, situated at the junction between carbon metabolism and nitrogen assimilation, because nitrogen compounds can choose an alternative pathway according to the stages of their growth and environmental conditions. The enzymes involved in the reactions are nitrate reductase (EC 1.6.6.1‐2), nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.1.13‐14, 1.4.7.1), glutamate dehydrogenase (EC 1.4.1.2‐4), aspartate aminotransferase (EC 2.6.1.1), asparagine synthase (EC 6.3.5.4), and phosphoenolpyruvate carboxylase (EC 4.1.1.31). Many of these enzymes exist in multiple forms in different subcellular compartments within different organs and tissues, and play sometimes overlapping and sometimes distinctive roles. Here, we summarize the biochemical characteristics and the physiological roles of these enzymes. We also analyse the molecular evolution of glutamine synthetase, glutamate synthase and glutamate dehydrogenase, and discuss the evolutionary relationships of these three enzymes.