A young boy presents with failure to thrive. Biochemical analysis of a aspirate after a meal reveals a deficiency of enteropeptidase (enterokinase). The levels of which digestive enzymes would be affected?
A. AmylaseB. Colipase
C. Lactase
D. Trypsin
The answer is D. Enteropeptidase
formerly called enterokinase activates trypsinogen by limited proteolytic
digestion to give trypsin is itself capable of activating trypsinogen, which
produces a positive feedback effect. Trypsin also activates chymotrypsinogen
(and several other proteolytic enzymes), so deficiency of enteropeptidase
results in a severe deficiency of enzymes that digest protein. Amylase aids in
the breakdown of starches to oligosaccharides, maltose, and maltotriose.
Colipase along with other lipases functions to digest fats.
Lactase is a
brush-border disaccharidase that hydrolyzes the bond between galactose and
glucose in lactose.
Pepsin is a proteolytic enzyme secreted
in an inactive form (pepsinogen) by the chief cells .of the stomach. Pepsinogen
is activated by stomach acid, and so is not dependent on enteropeptidase.
Pepsin alone will not replace the activities of other proteolytic enzymes,
partly because food does not remain in the stomach for an extended period of
time.
