Figure 2.

Biosynthesis pathways of amino acids and nucleotide triphosphates. Red colored digits indicate the number of reaction steps between the key metabolites. This diagram has been illustrated from the KEGG Pathway Database (25). Broken lines indicate supply of reactants. PEP is essential for making the aromatic benzene ring of Phe, Tyr and Trp. In addition, PRPP joins to form the indole moiety of Trp. While His is synthesized from PRPP with the help of ATP to make the imidazole moiety. Dotted lines may be for bypasses formed in later. All the aa pathways developed from F6P are divided into three groups; GA is on a nearest short path from F6P to Pyrv, GB is branched from TCA as a enzymatic circuit, and GC is based from the PPP core (see Figure 3B for details).