Sucrase

Sucrase is a digestive enzyme which breaks down sucrose into the simpler sugar glucose through hydrolysis. Also known as invertase or saccharase, it is not present in newborn animals so that they are unable to digest sucrose and feeding of the sugar will cause severe, osmotic diarrhea. Sucrase activity in the intestine increases with age as lactase decreases.

Sucrase is secreted by tiny, finger-like projections called villi which come out from the wall of the small intestine. Its levels are reduced in response to villi-blunting events such as celiac sprue and the inflammation associated with the disorder. The levels increase in Pregnancy/Lactation and Diabetes as the villi hypertrophy.

Chymotrypsin

Chymotrypsin is a digestive, proteolytic enzyme which breaks down proteins in the small intestine. Chymotrypsin is first produced by the pancreas as chymotrypsinogen, which is enzymatically inactive. Then chymotrypsinogen is carried in the pancreatic juice through the pancreatic duct into the duodenum (small intestine). There chymotrypsinogen is activated into chymotrypsin by another enzyme, trypsin, and by molecules of active chymotrypsin.

On cleavage by trypsin into two parts that are still connected via an S-S bond, cleaved chymotrypsinogen molecules can activate each other by removing two small peptides in a trans-proteolysis. The resulting molecule is active chymotrypsin, a three polypeptide molecule interconnected via disulfide bonds.

Chymotrypsin degrades peptides in the small intestine at the carboxyl side of tyrosine, tryptophan, and phenylalanine because these three amino acids contain aromatic rings, which fit into a 'hydrophobic pocket' in the enzyme. Over time, chymotrypsin also hydrolyzes other amide bonds, particularly those with leucine-donated carboxyls.