TABLE 1.

Loss of pathway-dedicated enzymesa

PathwayNo. of dedicated genesNo. of enzymes missing in:
AnimalsDictyosteliumPlasmodiumCryptosporidiumLeishmania
ILV555555
H777777
K333333
FW111111101011
R3    3b3332
T555555
M222221
S301332
  • a The biosynthetic pathways leading to these 11 amino acids involve multiple steps. The number of genes in each pathway in S. cerevisiae was taken from KEGG. The number of genes for each pathway that are missing in the other organisms was determined from their complete genomes. The amino acids are given in the single-letter code.

  • b C. elegans is missing all three genes of the arginine (R) biosynthetic pathway, but vertebrates have maintained them for use in the urea cycle (see text).