γ-Amino-n-butyric, aspartic, glutamic and pyrrolidonecarboxylic acid; their determination and occurrence in grass during conservation

Abstract

Simple quantitative methods, employing ionexchange resins, are described for the determination of Y -amino-n-butyric, aspartic, glutamic and pyrrolidonecarboxylic acid in plant material. The formation of the considerable amount of Y -aminobutyric acid found in silage and microbe-free grass is examined with respect to the glutamic acid and glutamine present. It seems to be derived from the glutamic acid and accumulates very rapidly under conditions unfavorable for the formation of glutamine. Balances have been worked out comparing the glutamic and aspartic acid found with the amounts expected from the proteolysis involved. All the glutamic acid appears to be recoverable, though a considerable part of it may exist as readily hydrolyzable bound glutamic acid of as yet undetermined structure. The amounts of pyrrolidonecarboxylic and Y -aminobutyric acid found in extracts of fresh grass are very small, and pyrrolidonecarboxylic acid probably does not exist as such in the grass, the little found being formed during the extraction.