Isolation of pyroglutamic acid from hypothalamic tissue and significance of its inhibition of prolactin release

Glutamic acid, twenty years later

This review examines progress in understanding the physiologic functions of glutamic acid in the body since the first symposium on glutamic acid physiology and biochemistry was held at the Mario Negri Institute in Milan in 1978. The topics reviewed, although not exhaustive, include the metabolism of glutamic acid, umami taste, the role of glutamic acid as a neurotransmitter, glutamate safety and the development of new drugs resulting from the knowledge of the neurodegeneration induced by high doses of glutamic acid.

Pyroglutamic acid. Non-metabolic formation, function in proteins and peptides, and characteristics of the enzymes effecting its removal

The formation of pyrrolidone carboxylic acid (PCA, pGlu) during protein biosynthesis is discussed. Studies are summarized which demonstrate that PCA is formed during the later stages of biosynthesis at the terminal phases of translation or as a post-translational event, just prior to cellular secretion of protein with amino-terminal PCA. Of the studies cited, the most convincing evidence suggests that PCA is derived from glutamine. Enzymes which selectivity remove PCA from the N-terminus, and of benefit in amino-acid sequence analysis, have been isolated and shown to have a ubiquitous distribution in various animal and plant cells. The investigations which lead to the isolation o these enzymes and the procedures for their use in removing amino-terminal PCA from proteins, are described. Finally, the biologic function of PCA and the effects of its chemical modification are discussed using the neuropeptide. Thyrotropin Releasing Factor (TRF) as a specific example.

A gas chromatographic method for the determination of N-acetyl-L-aspartic acid, N-acetyl-alpha-aspartylglutamic acid and beta-citryl-L-glutamic acid and their distributions in the brain and other organs of various species of animals

A simple and sensitive gas-chromatographic method for the determination of N-acetyl-L-aspartic acid (NA-Asp), N-acetyl-alpha-aspartylglutamic acid (NA-Asp-Glu) and beta-citryl-L-glutamic acid (beta-CG) was developed. The organ, regional and phylogenetic distributions of these compounds were studied. NA-Asp and NA-Asp-Glu were highly concentrated in nervous tissue, and less than 1% of the amounts in the nervous tissues were found in non-nervous organs. These two compounds showed a reciprocal relationship in their regional distribution in mature brains, but such a relationship was not evident or was even reversed in immature brains. The two compounds also showed different developmental changes in different regions of the brain. Fish brain contained a relatively high concentration of NA-Asp, but only a trace amount of NA-Asp-Glu. By contrast, a 10 times higher concentration of NA-Asp-Glu than NA-Asp was found in frog brain. Reptilian brain contained similar amounts of each compound. Avian and mammalian brain had NA-Asp at a roughly 10 times higher concentration than NA-Asp-Glu. beta-CG occurred at the highest concentration in the immature brain of rat and guinea pig, but disappeared in the mature brains. The adult frog brain, however, contained a large amount of beta-CG. In the adult rat, testis contained the highest concentration of beta-CG.