Figure 1

Essential amino acid anabolic pathways. Schematic representation for presence/absence of anabolic enzymes for nine essential amino acids and the non-essential amino acids serine and glycine. Eukaryotic taxonomic tree displayed at phyla level. Circles represent detection of complete proteins and triangles detection of complete and fragmented proteins. Black: phyla containing complete genomes; Grey: at most organisms with draft genomes; White: phyla with no complete or draft genomes. Saccharomyces cerevisiae (Ascomycota) and Arabidopsis thaliana (Streptophyta) were used as seeds. The 4 distinct aminotransferases in phenylalanine pathway are: (i) aspartate aminotransferase (ii) histidinol-phosphate aminotransferase (iii) aromatic amino acid aminotransferase (iv) tyrosine aminotransferase. The 4 distinct methyltransferases in methionine pathway are: (i) 5-methyltetrahydropteroyltriglutamate--homocysteine methyltransferase (ii) homocysteine S-methyltransferase (iii) betaine-homocysteine methyltransferase (iv) 5-methyltetrahydrofolate--homocysteine methyltransferase. The 3 distinct transaminases in glycine pathway are: alanine-glyoxylate transaminase, serine-glyoxylate transaminase and serine-pyruvate transaminase.