Soluble and membrane bound peptide hydrolases of the Holothuria forskali Delle Chiaje digestive tract

Five peptide hydrolases from the digestive epithelium of Holothuria forskali have been studied: two were membrane bound (designated M₁ and M₁₁) and three were cytosolic (S₁, S₁₁ and S₁₁₁). Initial studies revealed separate but overlapping substrate specificities. Of seven tripeptides tested with the soluble enzymes only L-Leu-L-Leu-L-Leu and L-Leu-Gly-Gly were hydrolysed, and then only by S₁₁. M₁ and M₁₁ also showed weak tripeptidase activity. Activity against dipeptides was considerably higher. In general the enzymes showed a preference for dipeptides having N-terminal hydrophobic aliphatic side chains.

The enzymes have been separated and partially purified, while S₁₁ was purified to homogeneity.