1. Basic Concept - Glutamine

Glutamine is the most abundant amino acid in plasma and is non-essential because it is synthesized by a ubiquitously expressed enzyme, glutamine synthetase. It is important for inter-organ nitrogen transport and has a central role in nitrogen and ammonia metabolism. It is an amino group donor for glucose precursors, other amino acids, purines and pyrimidines, and is a regulator of acid-base balance. In addition, it is regarded as having a major role in the pathophysiology of hyperammonaemia due to its osmotic effect on astrocyte swelling. Figure 4 shows the localization of the urea cycle and glutamine synthetase in different compartments of the liver as well as the intercellular glutamine cycling in relation to ureagenesis.

Figure 4. Nitrogen metabolism in liver (Ref 2)

See Ref. 3 for further reading.