EXTRACTION OF CAROTENOPROTEIN FROM BLACK TIGER SHRIMP SHELLS WITH THE AID OF BLUEFISH TRYPSIN

The effect of bluefish (Pomatomus saltatrix) trypsin on the recovery and characteristics of carotenoprotein from black tiger shrimp (Penaeus monodon) shells was investigated. Trypsin concentration and reaction time both affected the hydrolysis and the recovery of carotenoproteins ( P <  0.05). The recovery of carotenoproteins from shrimp shells was maximized by the hydrolysis of shrimp shells using 1.2 trypsin units/g shrimp shells for 1 h at 25C. Freeze-dried carotenoprotein recovered contained 70.20% protein, 19.76% lipid, 6.57% ash, 1.50% chitin, and 87.91 µg total astaxanthin/g sample, indicating a substantial reduction in the levels of antinutrients associated with shrimp waste, while enriching the product in carotenoid pigments and valuable essential nutrients (proteins and lipids). Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the recovered carotenoprotein revealed that protein with molecular weight of 45 kDa was the major constituent. When hydrolytic activities of bluefish and bovine trypsins toward carotenoproteins in black tiger shrimp shells were compared, the recovery efficacy of protein and pigment by bluefish trypsin was similar to that achieved by trypsin from bovine pancreas. Therefore, bluefish trypsin could be used as an alternative cheap proteinase for extraction of carotenoproteins from black tiger shrimp shells.

PRACTICAL APPLICATIONS

Carotenoproteins from black tiger shells, the byproduct of shrimp processing, can be recovered with the aid of fish trypsin. This product can be used for both food and feed applications. Additionally, the fish trypsin can be used instead of bovine trypsin. As a whole, the utilization of fish and shellfish processing wastes can be maximized.     

ENZYMATIC CHARACTERISTICS OF TRYPSIN FROM PYLORIC CECA OF SPOTTED MACKEREL (SCOMBER AUSTRALASICUS)

Trypsin was purified from the pyloric ceca of spotted mackerel (Scomber australasicus) by gel filtration on Sephacryl S‐200 and Sephadex G‐50. The purification and yield were 20‐fold and 81%, respectively, as compared to those in the starting crude extract. Final enzyme preparation was nearly homogeneous in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and the molecular weight of the enzyme was estimated to be 24,000 Da by SDS–PAGE. The trypsin was stable at pH 5–11 for 30 min at 30C, and its maximal activity against N^α‐p‐tosyl‐L‐arginine methyl ester was pH 8.0. Trypsin was heat‐stable up to about 50C for 15 min at pH 8.0. Optimum temperature of the trypsin enzyme was 60C. The enzyme was stabilized by calcium ion. The purified trypsin was strongly inhibited by serine protease inhibitors such as N‐p‐tosyl‐L‐lysine chloromethyl ketone and soybean trypsin inhibitor, suggesting that it is a trypsin‐like serine protease. N‐Terminal amino acid sequence of spotted mackerel trypsin was IVGGYECTAHSQPHQVSLNS.     

COMPARATIVE STUDY OF ENZYMATIC CHARACTERISTICS OF TRYPSINS FROM THE PYLORIC CECA OF YELLOW TAIL (SERIOLA QUINQUERADIATA) AND BROWN HAKELING (PHYSICULUS JAPONICUS)

Trypsins from the pyloric ceca of two fish species, yellow tail (Seriola quinqueradiata) and brown hakeling (Physiculus japonicus) were purified by a series of chromatographic separations. Purity increased 62‐ and 106‐fold with approximately 55 and 10% yield for yellow tail trypsin and brown hakeling trypsin, respectively. Final enzyme preparations were homogeneous in sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), and the molecular weights of both enzymes were estimated to be 24 kDa by SDS‐PAGE. Yellow tail and brown hakeling trypsins had maximal activity at pH 8.0 for hydrolysis of N_α‐p‐tosyl‐L‐arginine methyl ester hydrochloride and was unstable at acidic pH. The optimum temperatures for yellow tail and brown hakeling trypsins were 60 and 50C, respectively. Yellow tail trypsin was stable up to 50C, whereas brown hakeling was stable up to 40C. Both trypsins were stabilized by calcium ions. The activities of both trypsins were strongly inhibited by soybean trypsin inhibitor and N_α‐p‐tosyl‐L‐lysine chloromethyl ketone hydrochloride, and were partially inhibited by ethylenediaminetetraacetic acid. The N‐terminal amino acid sequences of yellow tail trypsin and brown hakeling trypsin were determined as IVGGYECTPYSQPHQVSLNS and IVGGYECPKHSQPHQVSLNS, respectively.     

COMPARATIVE STUDIES ON PROTEOLYTIC ACTIVITY OF SPLENIC EXTRACT FROM THREE TUNA SPECIES COMMONLY USED IN THAILAND

Proteolytic activities of splenic extract from three tuna species including skipjack tuna (Katsuwonus pelamis), yellowfin tuna (Thunnus albacores) and tongol tuna (Thunnus tonggol) were studied. Optimal activity of splenic extract from all tuna species was at pH 9.0 and 55C when casein was used as a substrate. Among all species tested, yellowfin tuna showed the highest activity, followed by skipjack tuna and tongol tuna. The proteolytic activity was strongly inhibited by soybean trypsin inhibitor, TLCK and partially inhibited by ethylenediaminetetraacetic acid. E‐64, N‐ethylmaleimide, iodoacetic acid, TPCK and pepstatin A showed no inhibition. The effect of NaCl and CaCl₂ on proteolytic activity was also investigated. Activities continuously decreased as NaCl concentration increased, and no activity remained in the presence of 30% NaCl. On the other hand, activities increased as CaCl₂ concentration increased. The highest activity was obtained in the presence of 1 mM CaCl₂. SDS‐substrate gel electrophoresis revealed that major proteinases in splenic extract from different tuna species were different in apparent molecular weights and sensitivity to TLCK. Although the major activity bands of all species were strongly inhibited by soybean trypsin inhibitor, varying sensitivity to TLCK probably implied the differences in binding characteristic of enzyme to substrate and/or inhibitors. The results suggest that major proteinases in spleen of all tuna species were trypsin‐like serine proteinases.