Digestive proteinases of red shrimp Pleoticus muelleri (Decapoda, Penaeoidea): partial characterization and relationship with molting

The present study describes the activity and some characteristics of protei nases in the hepatopancreas of red shrimp Pleoticus muelleri during the dif ferent stages of the molting cycle. Proteolytic activity was highest betwee n pH 7.5 and 8. The hepatopancreatic protein content in the premolt stage w as higher than in the other stages of the molting cycle (P < 0.05). No sign ificant differences were found in total proteolytic activity in the hepatop ancreas when comparing molting stages. The proteolytic activity of the P. m uelleri hepatopancreas enzyme preparations is the main responsibility of se rine proteinases. TLCK, a trypsin inhibitor, reduced azocasein hydrolysis b etween 26% (intermolt) and 37% (premolt). TPCK, a chymotrypsin inhibitor, d id not decrease hydrolytic activity, except for in postmolt. Low trypsin an d chymotrypsin activities were found during intermolt, and increased in pos tmolt. The electrophoretogram of the enzyme extracts shows 12 bands of acti vity during intermolt (from 16.6 to 53.1 kDa). Some fractions were not dete cted in the postmolt and premolt stages. Three low molecular weight trypsin forms (17.4, 19.1 and 20 kDa) were found in all molting stages. One band o f chymotrypsin (21.9 kDa) was observed in all molting stages. High molecula r mass active bands (66-205 kDa) could not be characterized with inhibitors . Comparison of the protease-specific activity of the hepatopancreas of som e species indicated a relationship between digestive enzyme activity and fe eding habits of the shrimp. Omnivorous shrimp, such as Penaeus vannamei (sy n: Litopenaeus vannamei) and Penaeus monodon, showed higher protease activi ty than the carnivorous shrimp, Penaeus californiensis (syn: Farfantepenaeu s californiensis) and P. muelleri. In fact, the enzymatic activity in the h epatopancreas of P. muelleri showed variations in relation to feeding habit and molting cycle. (C) 2001 Elsevier Science Inc. All rights reserved.