Glutamine and alanine are the major carriers of nitrogen among body tissues. These amino acids are largely synthesized in skeletal muscle [1]. The carbon skeleton of alanine is derived from glycolysis, through a pyruvate, whereas the carbon skeleton of glutamine is derived from the citric acid cycle, through alpha-ketoglutarate. The nitrogen used to form these amino acids is mainly derived from transamination of the branched chain amino acid (leucine, valine and isoleucine) [2] and from intracellular free ammonia. Alanine and glutamine are constantly released from skeletal muscle into the bloodstream, both in the fasting state and in the postaprandial phase. In the liver, alanine is the major amino acid precursor for gluconeogenesis. Glutamine is actively taken up by several tissues to serve as a precursor of many compounds, including hepatic glucose, urinary ammonia, intracellular gluthatione (through glutamate) and nucleic acids. Furthermore, glutamine is utilized for rapidly dividing cells of the intestinal mucosa and immune system [3].


Glutamine Synthetase Branch Chain Amino Acid Citric Acid Cycle Glutamine Synthesis Protein Kinetic 
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Copyright information

© Springer-Verlag Italia 2002

Authors and Affiliations

  • G. Biolo
    • 1
  1. 1.Department of Clinical, Morphological and Technological Sciences, Division of Internal MedicineUniversity of TriesteTriesteItaly

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