Questions & Answers

Pepsinogen is activated by
(a) Chymotrypsin
(b) Trypsin
(c) HCl
(d) Pepsin

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Hint: It is the principal protease in gastric secretions of adult mammals. They are members of the family of aspartic proteases, and closely associated with chymosin, another gastric protease expressed particularly in young animals. These compounds are integrated and discharged overwhelmingly by chief cells in the gastric mucosa.

Complete answer:
Pepsinogens are secreted during a form such as the activation peptide assumes a compact structure that occludes the site. On presentation to an acidic pH, the actuation peptide is severed, consequently exposing the site and creating chemically dynamic pepsin. The optimal activity of pepsins is at a pH of 1.8 to 3.5, depending on the isoform. They are reversibly inactivated at about pH 5 and irreversibly inactivated at pH 7 to eight.

Additional information: In general, the secretion of pepsinogens is coupled to the secretion of acid from the parietal cell.
In vitro examinations have exhibited that discharge is successfully invigorated by specialists that animate both of two conditions:
- Elevated intracellular degrees of cyclic AMP: models incorporate secretin, vasoactive intestinal peptide, and epinephrine.
- Elevated intracellular calcium: the main middle people examined incorporate acetylcholine and peptides of the gastrin/cholecystokinin family
Receptors for a few of the hormones recorded above are exhibited on boss cells and pepsinogen discharge has been animated or hindered by presentation to those operators or their adversaries, separately.
At the present time, it seems safe to say that the principal physiologic secretagogue(s) regulating pepsinogen secretion has not been clearly delineated.
So the correct answer is ‘(c) HCl’.

Note: Pepsinogen is the zymogen, or inactive precursor, of pepsin, the principal proteolytic enzyme of gastric juice. Pepsinogen was first crystallized from the gastric mucosa of swine, and a number of other pepsinogens have now been separated. The porcine pepsinogen features a relative molecular mass of roughly 43 kD and consists of the pepsin molecule and a number of other smaller peptides