Reaction products formed after strong acid treatment of alpha-amino-delta-hydroxyvaleric acid

High-voltage paper electrophoresis and analytical and preparative amino acid ion-exchange chromatography were used to investigate the products resulting from strong acid treatment and strong acid treatment and subsequent alkalinization of alpha-amino-delta-hydroxyvaleric acid. After strong acid treatment, alpha-amino-delta-hydroxyvaleric acid and proline, as well as several unidentified components, presumably lactones, were recovered. No definitive identification of the putative unstable lactones was accomplished either by physical-chemical means or by ion-exchange chromatography or high-voltage paper electrophoresis. Nevertheless, after acid treatment and alkalinization, only alpha-amino-delta-hydroxyvaleric acid and proline were recovered, in approximately equal amounts. The formation of such large amounts of proline from the acid treatment and alkalinization of alpha-amino-delta-hydroxyvaleric acid is therefore an important consideration in quantitating the number of gamma-glutamyl phosphate residues present in various proteins.