49B-15 |
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F. J. CINCO-MOROYOQUI and M. T. Villegas-Bailón. Departamento de Investigación y Posgrado en Alimentos, Universidad de Sonora, Apdo. Postal 1658, Hermosillo, Sonora, 83000, Mexico The brown shrimp Penaeus californiensisis the most abundant shrimp species in the Sea of Cortez which deteriorates rapidly during storage due to its high endoproteolytic activity. This study was carried out to determine the number and physicochemical character of the trypsin-like enzymes of this shrimp. The proteolytic activity was determined upon an aqueous crude extract by saturation with 80% ammonium sulfate. The precipitate formed was recovered and used as the source of enzymes. Analyses included native polyacrilamide gel electrophoresis (PAGE), molecular weight determination, heat stability at 70oC, optimum pH for activity, influence of inhibitors (b-mercaptoethanol, EDTA, and soy trypsin inhibitor) and activators such as calcium. By means of electrophoretic analysis the presence of at least 10 proteases were detected. The most active bands were designated A (50 Kda), B (14.5 Kda), C (12.4 Kda) and D (8.3 Kda) according to electrophoretic mobility. Inhibitory analyses showed that all the proteases were highly susceptible to the action of the soy trypsin inhibitor losing complete activity. Addition of 20 mM EDTA decreased the activity in 60%, but the use of the reducing agent b-mercaptoethanol did not affect any of the proteases. Use of 45 mM CaCl2 improve the enzyme activity of the extract only by 13%. The proteolytic extract showed the highest activity at pH 7 and an optimal temperature of 50oC; however, the extract was very unstable at 70oC losing more of 90% of its activity in 10 min. The properties of the trypsin-like enzyme activity of the brown shrimp determined in this study can be controlled to prevent loss of this marine product during its storage. Furthermore, the proteolytic enzymes of the brown shrimp can be also used in the commercial processing of diverse types of food products where enzymes are required.
Session 49B, Aquatic Food Products: General
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