No abstract

Four gelatinolytic proteinases (A1, 97 kDa; A2, 66 kDa; A3, 30 kDa; A4, 23 kDa) were detected from the red stingray wing muscle by gelatin zymography. Among these proteinases, major gelatinolytic proteinases (A1, A2) were more purified and examined their characters. The optimum pH and temperature for the gelatinolytic activity of A1 and A2 were around pH 7 and pH 8, and maximal activity of A1 is at 30–50C, that of A2 is at 30C. Also, they were demonstrated to hydrolyze the gelatin from red stingray; protein bands were almost completely degraded after 6 h incubation at 37C and pH 7.5. Both enzymes were strongly inhibited by Pefabloc SC, which suggests that they belong to gelatinolytic serine protease. PRACTICAL APPLICATIONS Gelatinolytic enzyme hydrolyzes denatured collagen such as gelatin. The enzymes from red stingray may be utilized to produce gelatin peptide, which has been widely used as additive to enhance the elasticity, consistency and stability of food products. In addition, it is meaningful in that this study will give information to understand the gelatinolytic proteinases in ray species and could lead to a comparative study of the biochemical properties of gelatinolytic proteinases in elasmobranch and many other species.

Gelatinolytic enzymes were partially purified from the skeletal muscle of red sea bream Pagrus major and characterized to obtain information on post mortem tenderization of fish muscle. Four gelatinolytic activities, G1 (90 kDa), G2 (65 kDa), G3 (60 kDa), and G4 (100 kDa), were detected in the Q Sepharose column. G1, the major gelatinolytic enzyme, and G4 were identified as serine proteinases from results of inhibitor spectrum and substrate specificity. By contrast, G2 and G3 were found to be metalloproteinases since these were inhibited by ethylenediamine tetraacetic acid and o-phenanthroline, and activated by 4-aminophenylmercuric acetate. The optimum pH and temperature of these enzymes were in the ranges of 7-9 and 20-40°C, respectively.

A translucent collagen gel was formed from a transparent acidic solution of red stingray collagen by adjusting to physiological ionic strength and pH in phosphate buffer and then incubating at 25-37°C. During fibril formation from red stingray collagen, the turbidity increased when the NaCl concentration was increased at constant pH and the rate of fibril formation was accelerated by higher pH or lower NaCl concentration. The T m of red stingray collagen fibrillar gel was estimated as 44.3 ± 3.5°C, which was higher than that of the collagen solution, 33.2°C. In addition, red stingray collagen gel maintained its shape without melting and was suitable for culture of mouse stromal cells at 37°C.

Collagen degradation is known to be involved in post mortem tenderization of fish muscle. A serine proteinase which is assumed to be related to collagen degradation after fish death was purified from sarcoplasmic fraction of red sea bream Pagrus major by ammonium sulfate fractionation and column chromatographies on Sephacryl S-300, Q Sepharose and Phenyl Sepharose CL-4B. The enzyme hydrolyzed gelatin and was obtained as a protein band of approximately 38 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis under reducing condition. N-terminal amino acid sequence of the enzyme was determined for 32 residues. The protein having the same N-terminal amino acid sequence of the enzyme for 10 residues was purified from the serum of red sea bream and showed the same characteristics as the enzyme. Therefore, the serine proteinase was suggested to migrate from blood to muscle and to degrade muscle proteins after fish death.