[Evolutionary patterns of the loss of amino acid biosynthesis in animals].

Amino acids, which synthesis was lost during animal evolution, exhibit some common physico-chemical features. These amino acids are presented by the largest molecules with the lowest density of packing of their material, the highest relative content of carbon and hydrogen, etc. It is suggested that during evolution there appeared living organisms which lacked the ability to produce various amino acids; however, natural selection fixed the loss of synthesis of only those amino acids which exhibited the above mentioned properties, as far as this loss did not interrupt vitally essential processes (glycolysis, tricarboxylic acid cycle, etc.) and did not result in elimination of these mutations. Loss of synthesis of these amino acids appeared to be favourable with respect to energy metabolism of the organism, since it made possible to "relay" some of the genes for another function.