Ornithine carbon catabolism

Enzymatic mechanisms dealing with the 5-amino group of ornithine, -amino group of lysine, indole-nitrogen of tryptophan, and the imidazole-nitrogen of histidine have not as yet been sufficiently well studied. Some reference to the fate of these nitrogen moieties will be made in the discussion of amino acid interconversions (see the chapters. Carbon Catabolism of Amino Acids, and Synthetic Processes InvolAung Amino Acids). 

Three of the amino acids, alanine, aspartic acid, and glutamic acid are readily formed by transamination from products of the citric acid cycle. This has been explained in the chapter. Carbon Catabolism of Amino Acids. Glutamic acid is the probable precursor of a considerable number of the other nonessential amino acids, namely, proline, hydroxy-proline, ornithine, and from it arginine. 

---