Type I collagen from the skin of ornate threadfin bream (Nemipterus hexodon): Characteristics and effect of pepsin hydrolysis

Type I collagen from the skin of ornate threadfin bream (Nemipterus hexodon) was purified and characterised. Purified type I collagen contained [α1(I)]₂α2(I) as the dominant component with the co-presence of α1(I)α2(I)α3(I). It was rich in glycine and alanine with high content of imino acids (188 residues/1000 residues). The maximum transition temperature (T_m) and the total denaturation enthalpy (ΔH) of purified type I collagen was 33.35 °C and 0.819 J/g, respectively. The isoelectric point (pI) of purified type I collagen was estimated to be 6.40. After hydrolysis of purified type I collagen using pepsin, the band intensity ratios of α1/α2-chains were increased (P < 0.05). The cross-linked components were effectively hydrolysed by pepsin 1 and 2 from skipjack tuna stomach and porcine pepsin at 4 °C without the cleavage of β- and α-chains. At 50 °C, they were more susceptible to porcine pepsin hydrolysis, followed by pepsin 2 and 1, respectively.