Figure 1.

Biosynthesis and metabolic uses of L-glutamic acid. The two alternative pathways from α-ketoglutarate (αKG) to glutamate (Glu) are shown by the thick arrows, as described by equations 1–4 in the Introduction. The gray arrow (left) represents equation 1, while the black arrow (right) represents the net sum of equations 2 and 3 (i.e., equation 4). Glu is one of the small minority of amino acids for which the great bulk of the molecules are used for purposes other than direct incorporation into proteins [2]. A number of transaminases use the α-amino group of Glu. Other uses of Glu were identified from the BioCyc website [63].