Evidence for the presence of N-Acetyl-α- l-aspartyl- l-glutamate in human brain

Abstract

A peptide composed of equimolar quantities of glutamic and aspartic acids was isolated from a protein-free extract of human brain by a combination of ion-exchange and paper chromatography. Hydrazinolysis studies established that glutamic acid was C-terminal and that the amino group of the aspartyl residue was substituted with an acetyl group. To determine which aspartyl carboxyl group was linked to glutamic acid, N-acetyl-α- and N-acetyl-β-aspartyl glutamate were synthesized. When the partial acid hydrolyzates of the synthesized acetylated peptides were chromatographed on the amino acid analyzer, two distinct elution patterns were observed. The elution pattern of the brain dipeptide resembled the alpha rather than the beta derivative. When acetylated amino acids prepared from brain dipeptide were incubated with hog l-specific kidney acylase, aspartic and glutamic acids were liberated.