Synthesis of Lysine from α,ɛ-Diaminopimelic Acid by Mixed Ciliated Rumen Protozoa

Abstract

LYSINE is essential to mammalian nutrition, but ruminants such as cattle, goats, sheep and so on can live on a lysine-deficient diet because the amino acid is synthesized by bacteria in the rumen¹. Although rumen ciliate protozoa are rich in lysine² it has been thought that they might not be able to synthesize lysine because of a statement (but no experimental proof) by Vogel³ that animal-type cells do not synthesize lysine. Guttman⁴ has, however, reported that some flagellated protozoa, trypanosomatids which all require lysine for growth, grew in a medium containing α,ɛ-diaminopimelate (DAP) but not α-aminoadipate instead of lysine. In connexion with our previous report⁵ that lysine was converted to pipecolate by rumen ciliates and that the latter acid was the end product in their lysine metabolism, we have proved directly that rumen ciliates can synthesize lysine from DAP with the following experiment.