Digestive enzymes of the shrimp Penaeus japonicus-I. Characteristics of amylase and protease of the shrimp Penaeus japonicus.

The characteristics of the primary digestive enzymes of the shrimp Penaeus japonicus were studied in animals fed for 30 days on a compounded dry diet containing 60% protein. Pepsin activity was not detected. A broad range of stable protease activity from pH 7.0-8.5 was found, indicating that perhaps more than one alkaline protease was detected by casein hydrolysis. Amylase activity showed a distinct activity optimum at pH 6.8. Optimum assay temperature for both amylase and protease was 40°C. The effect of Ca2+ addition on relative amylase activity was opposite to that of protease. This may indicate that maximal expression of amylase activity requires a greater amount of calcium than that of protease activity. Sufficient amounts of calcium for maximal expression of amylase activity did not seem to be supplied by either environment or dietary sources.