Proteolytic Activity of the Amoeba Mayorella Palestinensis

Lyophilized preparations of the soil amoeba Mayorella palestinensis hydrolyzed hemoglobin. Maximum cleavage occurred near pH 3. Mercapto compounds enhanced the activity only slightly, versene and iodoacetamide had no influence. Synthetic oligopeptides were also hydrolyzed by the preparations. Maximum degree of cleavage occurred at neutral or slightly alkaline pH values. While L‐leucylglycine was readily hydrolyzed, the D‐isomer of this peptide was not attacked. With DL‐leucylglycine 50% cleavage was obtained. Carbobenzoxy‐glycyl‐L‐phenylalanine and DL‐α‐bromoisocaproyl glycylglycine were not hydrolyzed while glycyl‐L‐phenylalanine and DL‐leucylglycylglycine were readily cleaved. Hemoglobin was very poorly hydrolyzed by the preparations at neutral or slightly alkaline pH values. However, preincubation of hemoglobin with the preparations at pH 2.7 rendered it available for further appreciable hydrolysis at pH 8. The significance of these findings for understanding the process of protein digestion in the food vacuole of protozoa is discussed.