Question

One of the constituents of the pancreatic juice which is poured into the duodenum in humans is -
(A) Trypsinogen
(B) Chymotrypsin
(C) Trypsin
(D) Enterokinase

Answer 1

Hint: The constituents of the pancreatic juice which is poured into the duodenum in humans is converted to its active form which is trypsin by the enzyme enteropeptidase, which is found in the intestinal mucosa.

Complete step by step answer:
Trypsinogen is the precursor form of enzyme trypsin which is a digestive enzyme. It is produced by the pancreas and poured into the duodenum and found in pancreatic juice, along with amylase, lipase, and chymotrypsinogen. The chemical formula of trypsin is ${ C }_{ 39 }{ H }_{ 55 }{ N }_{ 9 }{ O }_{ 17 }$.

So, the correct answer is ‘Trypsinogen’.

Additional Information: Trypsinogen is activated by enteropeptidase which is also known as enterokinase. Enterokinase is produced by the layer mucosa of the duodenum and it cleaves the peptide bond of trypsinogen after residue 15, which is lysine. The N-terminal peptide is discarded, and a slight rearrangement of the folded protein takes place. The terminal which is formed newly i.e N-terminal residue inserts into a cleft, where its α-amino group forms an ion pair with the aspartate near the active site serine and results in the conformational rearrangement of other residues. The amino group of Glycine orientates itself into the correct position, which completes the oxyanion hole in the active site, thereby activating the protein. As you know that trypsin also cleaves the peptide bond after arginine or lysine, it can cleave another trypsinogen, and the activation process, therefore, becomes autocatalytic.

Note: Trypsinogen is stored within the pancreas so that it should be released when required for protein digestion. The pancreas stores the inactive form of the enzyme trypsin i.e trypsinogen because the active trypsin would cause severe damage to the tissue of the pancreas. Trypsinogen is released by the pancreas along with other digestive enzymes. into the second part of the duodenum, via the pancreatic duct.