DEGRADATION OF PROTEINS BY GUINEA-PIG INTESTINAL ENZYMES

Insulin, insulin B-chain, albumin and azoalbumin were used as model proteins to evaluate the proteolytic activity of different gastrointestinal tract sections in guinea pigs. Brush border membrane enzymes and luminal enzymes (supernatant and pellet) were isolated from the small intestine and colon of guinea pigs and the cleavage of the above mentioned proteins studied. The results clearly indicate that small intestine brush border and luminal enzymes possess a higher proteolytic activity compared to the colon. The total proteolytic activity of the small intestine toward insulin and insulin B chain was 4.4 and 12 times greater, respectively, than of the colon. The degradation patterns of insulin and insulin B chain cleavage by small intestinal luminal enzymes at about 50% degradation were compared with those of chymotrypsin, trypsin and elastase. While the insulin degradation occurred by all three enzymes, the insulin B chain was predominantly cleaved by trypsin. The degradation rate of unfolded proteins, i.e., insulin B chain and azoalbumin was much faster than the degradation rates of insulin and albumin, both with luminal and brush border membrane enzymes. The results obtained support the hypothesis that the colon demonstrates decreased enzymatic activity (compared to SI) and is a route for possible oral administration of protein drugs.