Utilization of Glutamine and Asparagine and their Peptides by Micro-organisms

Abstract

ALTHOUGH the utilization of asparagine and glutamine by micro-organisms has been studied in recent years, nothing is known about the metabolism of their simple peptides. Aspartic acid can support optimal growth of Leuconostoc mesen-teroides; but asparagine is utilized only to a small extent^1,2. It has recently been found in this laboratory that the utilization of asparaginylglycine and glycylasparagine approximates that of the free di-carboxylic acid, and is better by far than that of asparagine². The same was found to be true for Lactobacillus arabinosus under conditions of incubation that precluded the endogenous synthesis of aspartate (26° in vacuo over potassium hydroxide or 39°)³. On the other hand, glycylglutamine and glutaminylglycine replace glutamine molecule for molecule in the metabolism of L. arabinosus, and the organism grows in synthetic media containing the peptides or the free amide without the lag period characteristic of its growth in media containing glutamic acid. It has been shown previously that the sulphoxide derived from methionine competitively inhibits the utilization of glutamic acid, but has no effect on the utilization of glutamine⁴. In this respect, too, the glutamine peptides behave exactly as the free amide².