Ammonia, glutamine, and asparagine: a carbon–nitrogen interface

Abstract

In plants, the primary input of nitrogen (obtained from the soil or from symbiotic dinitrogen fixation) occurs through the assimilation of ammonia into organic form. Synthesis of glutamine (via glutamine synthetase) is the major, and possibly exclusive, route for this process, and there is little evidence for the participation of glutamate dehydrogenase. A variety of reactions distribute glutamine nitrogen to other compounds, including transfer to amino nitrogen through glutamate synthase. In many plants asparagine is a major recipient of glutamine nitrogen and provides a mobile reservoir for transport to sites of growth; ureides perform a similar function in some legumes. Utilisation of transport forms of nitrogen, and a number of other metabolic processes, involves release of ammonia, which must be reassimilated. In illuminated leaves, there is an extensive flux of ammonia released by the photorespiratory cycle, requiring continuous efficient reassimilation. Aspects of ammonia recycling and related amide metabolism in higher plants are reviewed.

Anticancer Activity of L-Asparaginase Produced from Vigna Unguiculata

“…The L-asparaginase (E.C.3.5.l.l) an aminohydrolasecatalyses effect involved asparagine hydrolysis to yield L-aspartate and ammonia [2,14,17]. L-glutamine to L-glutamate as well as L-asparagine transamination [17,18]. Several investigators [8,14,19] reported an internal and external L-aspargenases were biochemically and genetically distinct in different plants.…”

Biochemical and molecular characterization of transgenic Lotus japonicus plants constitutively over-expressing a cytosolic glutamine synthetase gene

“…GS 1 plays a major role in the assimilation of ammonia derived from N 2 fixation in the nodules and also has an important role in the remobilization of nitrogen during senescence, bacterial infection, herbicide treatment and water stress (Bauer et al 1997;Pérez-García et al 1998;Brugiere et al 2000;Masclaux et al 2000). GS 1 is the main isoform involved in the assimilation of external ammonia (Sukanya et al 1994) and the ammonia derived from other sources of nitrogen, like the synthesis of secondary metabolites and the recycling of nitrogen from protein catabolism (Joy 1988). Root GS 1 may also have a role in the assimilation of the ammonia derived from nitrate reduction in the roots (Lancien et al 1999).…”

Physico-chemical properties and amino acid profiles of sap from Tunisian date palm

“…Similar to most plants, the free amino acid pool of both male and female saps (Table 3) was dominated by glutamine, asparagine (Fischer et al, 1998), and arginine (Salaün and Charpentier, 2001). In fact, the synthesis of glutamine is the major pathway for the assimilation of ammonium into organic matter, and asparagine represents the major receiver of the nitrogen of glutamine and a mobile reservoir for transport to growth sites (Joy, 1988). Arginine, on the other hand, is a precursor of the biosynthesis of polyamines and nitric oxide, which are involved in almost all physiological and biochemical processes as well as in plant growth and adaptation to stress (Yang and Gao, 2007).…”