Feeding and Digestion 



167 



TABLE 27 (continued) 

 CHARACTERISTICS OF EXOPEPTIDASES (POLY- AMD DLPEPTIDASES) 



carboxvpeptidase occurs along with trypsinogen in the pancreatic juice; amino- 

 peptidase and dipeptidase together constitute the enzyme formerly called 

 erepsin of the intestinal juice and may act intraccllularly. There is evidence 

 that mammalian intestinal mucosa elaborates an enzyme leucylpeptidase, in 

 addition to aminopeptidase and dipeptidase. Leucylpeptidase attacks leucyl- 

 diglycine but not triglycine, and is activated by magnesium ions.'*"'' **"' Car- 

 boxypeptidase occurs separately from the other peptidases in several animal 

 groups. In Paramecitnn extracts the carboxypeptidase is said to be activated 

 by cathepsin activators (H^S, HCN, cysteine); the aminopeptidase and the 

 dipeptidase are not. ^'^^ In the onychophoran Peripatopsis the saliva contains 

 a carboxypeptidase alone, and the gut in general contains the three pepti- 

 dases. "^ Similar separation of carboxypeptidase occurs in Murex ^^^ and 



