Peptidase activities of extracts of salivary glands of Drosophila melanogaster.

1. Peptide-splitting enzymes have been studied in buffered glycerine extracts of larval salivary glands of three stocks of Drosophila melanogaster. 2. The ultraviolet absorption spectrum of the glycerine extracts indicates the presence of a considerable amount of nucleic acid. 3. Alanylglycine (AG), leucylglycine (LG), leucylglycylglycine (LGG), glycylglycine (GG), and diglycylglycine (GGG) are split by the gland extracts in descending order of activity. 4. Of the various metals added, manganese was the only one found to give clear cut activation and that only with LGG as substrate. Cysteine inhibited the splitting of both AG and LG. 5. Comparison of the data with those published indicates the presence in the extracts in descending order of activity (at pH 7.6, 40 degrees C.) of at least four enzymes: an AG-dipeptidase, an LG-dipeptidase, a leucineaminopeptidase, and possibly an aminopolypeptidase. 6. Optimum conditions for the measurement of the enzyme splitting AG were determined. The pH activity and kinetic data are typical for an AG-dipeptidase. 7. An enzyme (probably cathepsin II) splitting benzoyl-l-arginineamide (pH 5.0) with cysteine activation was observed to occur with very low activity in gland extracts.