Racemization of Amino Acids in Dipeptides Shows COOH > NH2 for Non-Sterically Hindered Residues

See allHide authors and affiliations

Science  15 Feb 1980:
Vol. 207, Issue 4432, pp. 765-767
DOI: 10.1126/science.207.4432.765


The relative rates of racemization for amino acid residues at the NH2 and COOH ends of 37 different dipeptides were determined. In nine dipeptides containing alanine, leucine, phenylalanine, aspartic acid, and methionine, the amino acid residue racemized faster at the COOH-terminal position than at the NH2-terminal position (COOH > NH2). The sterically hindered amino acids isoleucine and valine showed NH2 > COOH. Six proline dipeptides showed NH2 > COOH. Intramolecular effects have been invoked to explain these surprising results.