title: Detection of diastereomer peptides as the intermediates generating D-amino acids during acid hydrolysis of peptides.
abstract: In this study, we investigated whether the amino acid residues within peptides were isomerized (and the peptides converted to diastereomers) during the early stages of acid hydrolysis. We demonstrate that the model dipeptides L-Ala-L-Phe and L-Phe-L-Ala are epimerized to produce the corresponding diastereomers at a very early stage, prior to their acid hydrolytic cleavage to amino acids. Furthermore, the sequence-inverted dipeptides were generated via formation of a diketopiperazine during hydrolytic incubation, and these dipeptides were also epimerized. The proportion of diastereomers increased rapidly during incubation for 0.5-2 h. During acid hydrolysis, C-terminal residues of the model dipeptides were isomerized faster than N-terminal residues, consistent with the observation that the D-amino acid values of the C-terminal residues determined by the 0 h-extrapolating method were larger than those of the N-terminal residues. Thus, the artificial D-amino acid contents determined by the 0 h-extrapolating method appear to be products of the isomerization of amino acid residues during acid hydrolysis.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.|Department of Pharmaceutical and Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Miyamoto
authors.affiliation: Department of Pharmaceutical and Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
authors.forename: Masae
authors.initials: M
authors.lastname: Sekine
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Tetsuhiro
authors.initials: T
authors.lastname: Ogawa
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hidaka
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Pharmaceutical and Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan. hommah@pharm.kitasato-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Homma
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. amasaki@mail.ecc.u-tokyo.ac.jp.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Masaki
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D006868:Hydrolysis; D010455:Peptides / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D010455:Peptides
keywords: D-Amino acid; Diastereomer; Dipeptide; Hydrolysis; Isomerization; Racemization