title: Oxidative fragmentation of collagen and prolyl peptide by Cu(II)/H2O2. Conversion of proline residue to 2-pyrrolidone.
abstract: Oxidative degradation of collagen and the model peptides by Cu(II)/H2O2 has been studied. The depolymerization of collagen was predominantly observed by use of gel filtration chromatography. Polyproline was used as a model for collagen, and the oxidative modification was examined by amino acid analysis. Glutamic acid and gamma-aminobutyric acid were identified in the hydrolysates of oxidized polyproline. The formation of glutamic acid was reduced by treatment with NaBH4. The model peptide, (Pro-Pro-Gly)10, was also degraded by Cu(II)/H2O2, and a new N-terminal glycine was generated in proportion to the reaction time. Hydroxyl radical scavengers show only partial inhibition of the degradation of (Pro-Pro-Gly)10. In order to estimate the fragmentation mechanism, we used N-tert-butoxycarbonyl (Boc)-L-prolylglycine as a model for collagen and (Pro-Pro-Gly)10. The degradation products were isolated and characterized. Then N-tert-Boc-2-pyrrolidone, which provides gamma-aminobutyric acid by acid hydrolysis, was identified. The formation of a 2-pyrrolidone compound from oxidized Boc-L-prolylglycine is direct evidence for the scission of the peptide bond. The time-dependent formation of N-tert-Boc-2-pyrrolidone and liberation of glycine from N-tert-Boc-L-prolylglycine exposed to Cu(II)/H2O2 was observed. These results suggest that the cleavage of the peptide bond (Pro-Gly) was caused by oxidation of the proline residue, which led to the formation of the 2-pyrrolidone compound. We confirmed that proline oxidation leads to the fragmentation of proteins, accompanied by the formation of a 2-pyrrolidone structure.
authors.affiliation: Department of Food Science & Technology, Nagoya University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: K
authors.initials: K
authors.lastname: Uchida
authors.forename: S
authors.initials: S
authors.lastname: Kawakishi
mesh_terms: D000595:Amino Acid Sequence; D001894:Borohydrides; D002851:Chromatography, High Pressure Liquid; D003094:Collagen / Q000737:chemistry*; D003300:Copper; D005260:Female; D006801:Humans; D006861:Hydrogen Peroxide; D007202:Indicators and Reagents; D007700:Kinetics; D008353:Mannitol; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry* / Q000302:isolation & purification; D010920:Placenta; D011247:Pregnancy; D011392:Proline; D011760:Pyrrolidinones; D013997:Time Factors
chemical_list: D001894:Borohydrides; D007202:Indicators and Reagents; D010455:Peptides; D011760:Pyrrolidinones; C011083:polyproline; D008353:Mannitol; D003300:Copper; D003094:Collagen; D011392:Proline; D006861:Hydrogen Peroxide; C028537:2-pyrrolidone