Glutamate, arginine from biosynthesis

Fig. 66 (Davis)—Biosynthesis of arginine from glutamic acid.

FIGURE 20.13 Biosynthesis of arginine and proline from glutamate. The key step is a partial reduction of glutamate to the corresponding aldehyde. 

The nitrogen of the basic amino acids lysine, histidine and arginine is not derived from wort amino acids but possibly from ammonium ions. In these cases intracellular oxoglutarate is aminated with ammonia to produce glutamate for biosynthesis. The imino acid proline is synthesized, without... 

If it is demonstrated that there is no involvement of arginine in the biosynthesis of TTX, this discussion should be moved to another chapter. Yet, if TTX is considered to be an alkaloid derived from an amino acid and a C5 unit, there is an another example similarly derived. Namely, kainic acid (6.1) is shown to be derived from a glutamic acid and a C5 unit. It is noteworthy that both of these very interesting, biologically active alkaloids, TTX and kainic acid, obtained from marine organisms in Japan, are derived from an amino acid and a C5 unit. 

Alkaloids Derived from the Krebs Cycle (Lysine and Ornithine Derived) As shown previously (Scheme 1.2), the Krebs cycle is a crucial metabolic process, which leads to a-ketoacids (oxaloacetic and 2-oxoglutaric acids). Their enzymatic transamination affords the two amino acids— aspartic acid and glutamic acid—which are the direct biosynthetic precursors of amino acids lysine and ornithine, respectively. These in turn produce cadaverine, a CjN unit, and putrescine, a C N unit, which are major components for the biosynthesis of important alkaloids, as will be discussed later (Scheme 1.6). Additionally, ornithine is a precursor of arginine, another important amino aeid. 

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