Correlation of proline, hydroxyproline and serine content, denaturation temperature and circular dichroism analysis of type I collagen with the physiological temperature of marine teleosts.

Fish products are a promising source of collagen; however, these extracts are biochemically unstable. Acid-soluble collagen (ASC) was isolated from the skin of eleven fish species at various physiological temperatures (Tp). Structural features of these samples were analysed in detail using Circular Dichroism (CD) and compared to their biochemical characteristics. Positive correlation (r = 0.74, p < 0.01) between the Tp and ratio of positive peak intensity to negative peak intensity (Rpn) in CD analysis suggested a higher thermal stability of ASC from warm-water fish, owing to a higher content of cyclic imino acids, such as proline and hydroxyproline (Hyp). Conversely, cold-water fish ASCs contain significantly higher levels of acyclic, hydroxyl groups carrying Ser. These results indicated that CD spectrum techniques including Rpn measurement are concise and helpful for direct detection of the triple helix structure of fish collagens, and that this structure is tightly linked to thermostability of this molecule.

Biochemical study of type I collagen purified from skin of warm sea teleost Mahi mahi (Coryphaena hippurus), with a focus on thermal and physical stability.

Acid- and pepsin-soluble collagen were purified from the skin of mahi mahi (mmASC and mmPSC). The Pro+Hyp content of the latter (185/1,000 residues) was highest among all marine teleost fishes. Fourier transform infrared spectroscopy and Circular Dichroism (CD) analysis showed the typical structure of type I collagen. The ratio of positive over negative peak intensity calculated from the CD spectrum was approximately 1.19 in mmPSC, which is remarkably high, and indicates the stability of the triple helix. The denaturation temperatures (Td ) of mmASC and mmPSC were the highest (29.5 and 28.8°C, respectively) among the marine teleost fishes previously studied. atomic force microscope and scanning electron microscope images showed that even after pretreatment, the fibrils presented their structure and fiber orientation. These results indicate the robustness of both collagens, which can be attributed to the high value of Pro+Hyp stabilizing the helix structure of the collagen molecule. Practical applications While Mahi mahi is highly valuable for its meat, other parts such as skin is not fully utilized in seafood industry. On the contrary, it has been empirically shown that the skin of Mahi mahi has high thermal stability, thus, the skin has been used for leather products in some areas located in the tropical and subtropical zones. In this study, we focused on collagen a major component in skin and investigated the structure and the biochemical characteristics of it. Some results showed that collagen from skin has high physical stability. The collagen from skin of Mahi mahi will be a new fishery resource which could be used as a material for collagen products.