Isolation and characterisation of acid and pepsin-solubilised collagens from the skin of Brownstripe red snapper (Lutjanus vitta)

Acid-solubilised collagen (ASC) and pepsin-solubilised collagen (PSC) were successfully extracted from the skin of Brownstripe red snapper (Lutjanus vitta) with yields of 9% and 4.7%, respectively, on the basis of wet weight. Both ASC and PSC consisted of two different α chains (α1 and α2), and were characterised to be type I with no disulfide bond. PSC had a lower content of high molecular weight cross-links, than did ASC. Peptide maps of ASC and PSC hydrolysed by V8 protease and lysyl endopeptidase showed some differences in peptide patterns between the two fractions and were totally different from those of calf skin collagen type I, suggesting differences in amino acid sequences and collagen conformation. Maximum solubility in 0.5 M acetic acid was observed at pH 3 and pH 4 for ASC and PSC, respectively. A sharp decrease in solubility was observed in the presence of NaCl, above 2% and 3%, (w/v) for ASC and PSC, respectively. Tmax values of both collagen fractions were similar and shifted to a lower value in the presence of acetic acid, suggesting some changes in the collagen structure caused by acid induction.