Isolation and Identification of Urinary β-Aspartyl Dipeptides and Their Concentrations in Human Urine

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Abstract
β-Aspartyl-methionine, -aspartic acid and -glutamic acid and γ-glutamyl-threonine and -glycine were isolated and identified in human urine by means of ion-exchange chromatography, high-voltage paper electrophoresis, acid hydrolysis and determination of N-terminal amino acids of the isolated compounds, and comparison of their behaviors in paper electrophoresis and chromatography with those of the authentic compounds. The concentrations of acidic β-aspartyl dipeptides in human urine were determined using an amino acid analyzer. Their concentrations were as follows: β-aspartyl-glycine, male, 44.4±8.5, female, 61.4±18.9, child, 83.7±27.1; -alanine, male, 11.0±4.9, female, 20.7±12.0, child, 25.3±9.1; -glutamic acid, male, 10.0±3.7, female, 23.0±8.5, child, 20.4±7.5; -serine, male, 9.9±2.8, female, 13.6±3.8, child, 14.9±4.7; -aspartic acid, male, 4.3±1.0, female, . 9.1 ±2.2, child, 18.4±6.5; -threonine, male, 3.9±0.9, female, 5.8±1.1, child, 13.2±4.9 μmol/g creatinine (mean±S.D.). The order of the sum of their concentrations tended to be child > female > male. Patients receiving intravenous hyperalimentation also excreted acidic β-aspartyl dipeptides into urine in amounts similar to those in females and in a pattern similar to that observed in healthy persons. This finding indicates that urinary β-aspartyl dipeptides were probably of endogenous origin because oral nutrition was stringently excluded in these patients.