Comparison of digestive proteinases in three penaeids

Recently, several groups of researchers reported that besides serine proteinases, other classes of proteinases may be involved in crustacean's food protein digestion, including cysteine and aspartic proteinases. In this paper, a comparative study of the class and type of digestive proteinases of whiteleg shrimp Penaeus vannamei, blue shrimp Penaeus stylirostris, and yellowleg shrimp Penaeus californiensis is addressed, along with some operational characteristics. The substrate-SDS-PAGE zymogram of the three species showed varieties of different proteinases that were species-specific and proteinase composition that may be used for species identification or population studies. In the three species, trypsin and chymotrypsin were present as isoenzymes. Some active bands were active at acid pH and were partially inhibited by pepstatin A and based on bibliography information they are digestive enzymes. The involvement of these enzymes in food protein digestion is discussed and compared with digestive enzymes present in other decapod species. This and additional information expand the knowledge about enzyme food protein digestion in crustaceans, making clear that digestion process is more complex than previously alleged and if common patrons exist, there are some individualities. This information opens a line of research trying to fully understand the mechanism of protein digestion.