Effect of feed diet on aminopeptidase activities from the hepatopancreas of white shrimp (Penaeus vannamei)

White shrimp (Penaeus vannamei) were fed one of seven diets for 30 days. Di ets contained 85% of a reference ration and 15% of either anchovy, tuna was te meal, deboned fish meal, langostilla crab meal, soybean meal, menhaden m eal A, or menhaden B as a protein replacer. At the end of the feeding trial , animals were sacrificed and 10 aminopeptidase activities of the hepatopan creas tissue were assayed. The hepatopancreas tissues contained Arg-, Leu-, His-, Ile-, Lys-, Met : Thr- and Val-aminopeptidase activities bur no acti vity was detected for Phe-aminopeptidase. Leu-aminopeptidase activity was i nhibited by Zn+2 and Mg+2 salts and activity was also inhibited when more t han 0.2 mg of hepatopancreas extract protein was included in the assay. Pri ncipal component analysis was used to determine whether diet had an influen ce on hepatopancreas aminopeptidase activities. The aminopeptidase activiti es were greater for animals fed a diet containing menhaden fish meal B. Thi s was principally the result of the higher levels of Met-, Val-, Pro-, Lys- , and Leu-aminopeptidase activities in animals fed menhaden fish meat. Menh aden fish meal B had a lower nutritional quality for shrimp than the other protein replacers. Seven of the 10 essential amino acids for shrimp were pr esent at less than 100% of the recommended values. On the other hand, shrim p fed soybean meal replacer contained lower amounts of aminopeptidase activ ity, notably Gly- and Met-aminopeptidase activities, and the meal was of ex cellent quality having only one limiting amino acid. The results indicate t hat the shrimp diet can influence proteolytic activity of the hepatopancrea s tissue. This is significant to the seafood technologist since previous st udies showed that hepatopancreas proteases can leach into the meat postmort em and cause tissue softening.