*2.2. Amino Acid Content*

The amino acid profiles of blue shark collagens (PSC and ASC) were similar in trend and expressed as residues per 1000 total residues (Table 1). Both ASC and PSC had glycine (392 and 387) as a foremost amino acid, followed by alanine (144–130) and proline (132–124). The amino acid contents of glycine, asparagine, proline, and hydroxyl-proline were high in general. The sum of Pro and Hyp (imino acid) content was higher in PSC (222) than ASC (213). The high content of alanine, glycine, hydroxyproline, and proline were the typical amino acids that represent the high content of collagen in blue shark skin. The present finding of collagen amino acid composition was similar to other fish collagen [16,17]. The differing amino acid composition between PSC and ASC was due to the removal of some non-collagen amino acid and the breakdown of certain specific amino acid residues at the telopeptide region during pepsin hydrolysis.


**Table 1.** The amino acid composition of ASC and PSC from blue shark skin.
