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Oxidative degradation of collagen and its model peptide by ultraviolet irradiation

Kato, Y., Uchida, K., Kawakishi, S.
Journal of agricultural and food chemistry 1992 v.40 no.3 pp. 373-379
collagen, peptides, degradation, oxidation, ultraviolet radiation, food quality, food spoilage
The effects of ultraviolet irradiation on collagen and its model peptides were studied. Degradation of collagen was predominant in the system using gel filtration chromatography. The fragmentation was presumably due to oxidation of proline, since collagen is a proline-rich protein and proline residues on collagen markedly decreased with irradiation. To clarify the fragmentation mechanism, Poly(L-proline) and (Pro-Pro-Gly)10 as models of a collagen molecule were used and their oxidation was investigated. Glutamic acid, gamma-aminobutyric acid (GABA), and ammonia from the hydrolysates of the irradiated prolyl peptides were identified by amino acid analysis. It was presumed that GABA was generated from a 2-pyrrolidone structure by acid hydrolysis. To confirm this prediction, N-tert-butoxycarbonyl (Boc)-L-proline and N-tert-Boc-L-prolylglycine were exposed to ultraviolet light, and the irradiation products were isolated and characterized. Then, N-tert-Boc-2-pyrrolidone was identified from both UV-irradiated N-tert-Boc-L-proline and N-tert-Boc-L-prolylglycine. We proposed that the formation of the 2-pyrrolidone compound must contribute to the fragmentation of prolyl peptide on the basis of its structural property.