Observations on the proteolytic enzymes in the digestive fluid of the barnacle Balanus nubilus

Abstract

1. 1. Digestive fluid extracts of the barnacle Bolanus nubilus examined within 24 hr after capture were found to have a pH value of 5.3, which is in the range for many decapod crustaceans. 2. 2. In contrast, the protein content in the range of less than 2 per cent was lower than that found for many decapods even after starvation. 3. 3. Most of the proteinase activity of the digestive fluid was confined to the acid range, and the pH optimum varied between pH 3.5 and 6.4 depending on whether hemoglobin, azocasein or casein was used as the substrate. 4. 4. Based on electrophoretic studies of the digestive fluid, most of the acid proteinase activity could be attributed to a single component. It is not known whether the acid proteinase is exogenous or endogenous in origin. 5. 5. An electrophoretic comparison of proteinases of glandular and digestive fluid extracts produced no proteinases of common electrophoretic mobilities. However, evidence is presented that indicates several additional proteinases are present in low concentrations in the digestive fluid and are involved in extracellular digestion.