Digestive enzymes in juvenile green abalone, Haliotis fulgens, fed natural food.

Enzymes responsible for the digestion of food protein by juvenile green abalone (Haliotis fulgens) were studied when fed algae or a sea grass (Phyllospadix torreyi) naturally occurring in the habitat. The effect of food on the composition and activity of the enzymes was also evaluated. Acid, serine proteinases and aminopeptidases, as confirmed by pH profile of activity, specific inhibition and synthetic substrate hydrolysis were found in the digestive organs of juvenile green abalone. Algae and sea grass differentially affected the digestive system in abalone.

Digestive proteinases of Artemesia longinaris (Decapoda, Penaeidae) and relationship with molting.

Digestive proteinase activities of Artemesia longinaris were assayed at different stages of the molting cycle. Total proteolytic activity in the hepatopancreas was highest during postmolt. Trypsin and chymotrypsin activities were highest during intermolt. Specific inhibitors and zymograms of A. longinaris hepatopancreas extracts showed four trypsins (14.79, 15.49, 16.60, 17.38 kDa, respectively) and three chymotrypsins (21.38, 22.91, 27.54 kDa, respectively). Our results suggest that proteolytic activity in the hepatopancreas of A. longinaris is influenced by the molting cycle. Types and activity of prawn digestive enzymes constitute background information to further study the digestive abilities of these organisms and will lead to understanding their nutritional needs and feeding ecology.

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 proteinases in the hepatopancreas of red shrimp Pleoticus muelleri during the different stages of the molting cycle. Proteolytic activity was highest between pH 7.5 and 8. The hepatopancreatic protein content in the premolt stage was higher than in the other stages of the molting cycle (P<0.05). No significant differences were found in total proteolytic activity in the hepatopancreas when comparing molting stages. The proteolytic activity of the P. muelleri hepatopancreas enzyme preparations is the main responsibility of serine proteinases. TLCK, a trypsin inhibitor, reduced azocasein hydrolysis between 26% (intermolt) and 37% (premolt). TPCK, a chymotrypsin inhibitor, did not decrease hydrolytic activity, except for in postmolt. Low trypsin and chymotrypsin activities were found during intermolt, and increased in postmolt. The electrophoretogram of the enzyme extracts shows 12 bands of activity during intermolt (from 16.6 to 53.1 kDa). Some fractions were not detected 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 of chymotrypsin (21.9 kDa) was observed in all molting stages. High molecular mass active bands (66-205 kDa) could not be characterized with inhibitors. Comparison of the protease-specific activity of the hepatopancreas of some species indicated a relationship between digestive enzyme activity and feeding habits of the shrimp. Omnivorous shrimp, such as Penaeus vannamei (syn: Litopenaeus vannamei) and Penaeus monodon, showed higher protease activity than the carnivorous shrimp, Penaeus californiensis (syn: Farfantepenaeus californiensis) and P. muelleri. In fact, the enzymatic activity in the hepatopancreas of P. muelleri showed variations in relation to feeding habit and molting cycle.

Trypsin-like enzymes from two morphotypes of the 'living fossil' Triops (Crustacea: Branchiopoda: Notostraca).

Trypsin-like enzymes from two morphotypes (here called short and long) of the 'living fossil' Triops of Baja California Sur, Mexico were studied. Adults of both morphotypes were obtained from outdoor static cultures using dry soil from the natural habitats as a source of cysts and culture substrate. Individual and pooled extracts were made from dissected digestive tubes. The effect of pH and temperature on the trypsin activity was studied using N-alpha-benzoyl-DL-Arg-p-nitroanilide (BAPNA) as substrate. The highest proteolytic activity was found at the same pH with extracts of both morphotypes. At this pH, there was greater proteolytic activity at a lower temperature with the short morphotype extract than with the long morphotype extract. Substrate-SDS-PAGE zymograms showed bands of activity. Short morphotype extracts produced six bands; five of them were serine proteases of which three were trypsin-like enzymes. Long morphotype extracts revealed eight bands; six of them were serine proteases of which three were trypsin-like enzymes.

Characterization of fish acid proteases by substrate-gel electrophoresis.

Several analytical techniques based upon the use of substrate-polyacrylamide gel electrophoresis were evaluated to achieve characterization of aspartate proteases in fish stomach. Since aspartate proteases of fish are more stable at high pH than mammalian pepsins, the most accurate technique for activity assessment is electrophoresis at neutral pH and revealing of such activity at low pH with hemoglobin as substrate. The technique is suitable for characterization of proteases and in comparative assessment of acid protease activity in different sparids.