~ Pergamon 0305-0491(95)00039-9 Comp. Biochem. Physiol. Vol. I12B, No. 1, pp. 123-129, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0305-0491/95 $9.50 + 0.00 The digestive enzymes of the Pacific brown shrimp Penaeus californiensis II. Properties of protease activity in the whole digestive tract F. Vega-Villasante, H. Nolasco and R. Civera Department of Biochemistry of Experimental Biology Division. Centro de Investigaciones Biol6gicas de Baja California Sur. A.P. 128, La Paz 23000, B.C.S. M6xico Protease activity in the crude extract of the whole digestive tract from the brown shrimp Penaeus californiensis was found to have the following properties; (1) high halotolerance having maximum activity between 0 and 0.5 M NaCI but 50% maximum activity at 2 M NaCi; (2) optimal activity at 50°C; irreversible inactivation at 60°C; and (3) activity between pH 6 and 10 pH with maximum activity around 8. At least eight bands of activity were observed by using PAGE and agarose gels. Trypsin-like, chymotrypsin-like, carboxypeptidase A and B-like and leucine-aminopeptidase-like activity were detected in crude extract. Key words: Digestive enzymes; Halotolerance; Pacific brown shrimp; Penaeus californiens&; Protease activity. Comp. Biochem. Physiol. l12B, 123-129, 1995. Introduction Studies on the physiology of the hepatopancreas (Bunt, 1968; Loizzi, 1971; Gibson and Barker, 1979; Nakamura, 1987) have defined the role of hydrolytic enzymes in the digestive processes of crustaceans. The properties of the enzymes associated with the tract will determine the digestive capabilities of the organisms. The nutrition of aquatic organisms is essential to their profitable aquaculture, and the for- mulation of effective feed depends on our. knowledge of the nutritional biochemistry and physiology of the cultured species (Galgani, 1983). A knowledge of digestive enzymes in an organism helps to determine its digestive capa- bilities, which in turn helps the selection of ingredients to be included in a diet (Lee et al., 1980; Divakaran and Ostrowsky, 1990). The Correspondence to: F. Vega-Villasante, Department of Bio- chemistry of the Experimental Biology Division. Centro de Investigaciones Biol6gicas de Baja California Sur. A.P. 128, La Paz 23000, B.C.S. M~xico. Received 25 June 1994; revised 20 January 1995; accepted 21 January 1995. digestive enzymes of crustaceans have been studied over the last century for applications in physiology, biochemistry and food science (Lee, 1984; Jiang et al., 1991; Garcia-Carrefio, 1992). One important and expensive component for the penaeid shrimp diet is the proteic fraction. To assess the catalytic abilities of crustacean protein, it is important to understand the prop- erties of their digestive proteases (Galgani, 1988). The Pacific brown shrimp Penaeus cali- forniensis is distributed from California (U.S.A.) to Paita in northern Peru (Dore and Frimodt, 1987), and is considered as a viable species for cultivation on the Mexican Pacific coast. Only a few studies related to its biology, management and culture have been published (Galicia-Xicoht~ncatl, 1976; Rosales-Ju~irez, 1976; Kitani and Alvarado, 1982), and the nutritional requirements of these shrimp have received little attention (Brand and Colvin, 1977; Villarreal et al., 1990). Only recently are we beginning to understand the digestive enzymes of this species (Vega-Villasante et al., 1993; Civera et al., 1994). 123