Autophagy: possible origin of essential amino acids

This paper presents a hypothesis that can explain why similar essential amino acids requirements have been conserved among all heterotrophic eukaryotes. In an analysis of a food composition table, the first principal component of the amino acid compositions of daily foods was found to separate essential and non-essential amino acids. Regarding all foods from eukaryotes, this finding indicate that all eukaryotes have common components rich in essential amino acids. Previous studies have indicated that yeast, a eukaryote, can use its cytoplasmic components as a primary source of amino acids by autophagy, and all terrestrial organism cells showed similar amino acid compositions. If all eukaryotic cells depend on their cytoplasmic components as primary amino acid sources and if all eukaryotes maintain them rich in essential amino acids, it would be reasonable for heterotrophic eukaryotes to have lost the need to synthesize amino acids that are already stored inside their cells.