Comparison of two kinds of fish skin collagen and characterization of peptides from the digested collagen

In this study,pepsin soluble collagen(PSC)was extracted from the skin of cod(Gadus macrocephalus)and tilapia(Oreochromis niloticus). And the molecular structure,thermal stability and peptide sequence in digest mixtures were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis,Fourier transform infrared spectra,X-ray diffraction,amino acid composition analysis,rotary viscometer and high-performance liquid chromatography-tandem mass spectrometry. The results showed that collagens from two different sources were in accordance with the typical type Ⅰ collagen and had similar secondary structure and tertiary structure,but the amino acid composition were different. The proline hydroxylation rate of O-PSC(49.1%)was higher than that of G-PSC(33.3%). The thermal denaturation temperature of O-PSC(24.7 ℃)was higher than that of G-PSC(13.8 ℃),the thermal stability was closely related to the proline hydroxylation rate. After two kinds of collagen were treated with the same enzyme,the characteristic peptides could be detected and identified. Conclusion:Different types of collagen had similar structure,but the different peptide fragments would be produced after the same enzymatic hydrolysis,which could be used to identify the source of collagen and provided a basis for the establishment of rapid analysis.