Question

The enzyme enterokinase help in conversion of-
A) Caseinogen to casein
B) Trypsinogen to trypsin
C) Pepsinogen to pepsin
D) Proteins into polypeptide

Answer 1

Enterokinase is secreted into the intestine and therefore its function will be related to reactions happening in a basic environment.

Complete Answer:
Enterokinase, also known as enteropeptidase, is an enzyme. It is produced by cells of the duodenum, part of the small intestine. The enzyme is used in digestion in mammals. Trypsinogen is a zymogen of trypsin, a digestive enzyme. It is produced in the pancreas and secreted in pancreatic juice along with lipase, amylase, and chymotrypsinogen. Enterokinase converts trypsinogen into its active form trypsin. After activation, trypsin can itself cleave more trypsinogen into trypsin by a process called autoactivation. Trypsin cleaves the peptide bond on the carboxyl side of arginine and lysine which are basic amino acids. Absence of enterokinase results in impairment of intestinal digestion.
$TRYPSINOGEN\xrightarrow{{Enterokinase}}TRYPSIN$
$TRYPSINOGEN\xrightarrow{{Tryp\sin }}TRYPSIN$

Enterokinase is a serine protease, it consists of a disulphide linked heavy-chain of 82-140 kDa which anchors it in the intestinal brush border mucosa and a light-chain of 35–62 kDa which contains the actual catalytic subunit. Enterokinase is a member of the chymotrypsin group of serine proteases, and is structurally similar to these proteins. Enterokinase catalyses the hydrolysis of peptide bonds in proteins, it does not catalyze transfer of phosphate groups like other kinases. It has trypsin-like activity, it cleaves proteins following a lysine residue at a specific cleavage site.

Thus, the correct answer is B. trypsinogen to trypsin.

Note: Pepsinogen gets cleaved in an acidic environment by the action of HCl, caseinogen can only be cleaved in cud- chewing animals by the action of rennin, and proteins are converted into polypeptides by multiple enzymes, including enterokinase reaction being a part of it.