THE REGIONAL DIFFERENCES IN THE MUCOSAL-CELL LYSOSOMAL PROTEASES WITHIN THE RAT SMALL-INTESTINE

The specific aim of this study is to understand the distribution of ly sosomal enzymes along the intestine. The rat was used as the animal mo del. Intestinal homogenates were prepared from the jejunum, jejunoilea l junction, ileum, and caecum. Activities of lysosomal carboxypeptidas e A, dipeptidyl peptidase II, prolyl carboxypeptidase, and cathepsin B in homogenates were studied at pH 4.5 using specific substrates. Prol yl carboxypeptidase, cathepsin B, and dipeptidyl peptidase II had the highest activities in the caecum; carboxypeptidase A had the highest a ctivity in the jejunum. The ileum had the lowest activities of these f our lysosomal proteases. In summary, except carboxypeptidase A, the di stribution profiles of prolyl carboxypeptidase, cathepsin B, and dipep tidyl peptidase II are somewhat close. Carboxypeptidase A, prolyl carb oxypeptidase, and dipeptidyl peptidase II are all serine proteases but do not share similar intestinal distribution profiles.