BIOCHEMISTRY OF PANCREATIC JUICE

1. BIOCHEMISTRY OF PANCREATIC
JUICE
By
Dr KHALED ALGARIRI
CAMS- QASSIM UNIVERSITY
APRIL2020

2. INTRODUCTION
Pancreas is elongated gland lies
behind and below the stomach.
Pancreas has Acini and ducts.
1. - Pancreatic Acinar cells secrete –
digestive enzyme.
2. - Pancreatic duct – secrete
watery secretion rich in NaHCO3

3. COMPOSTION OF PANCREATIC JUICE
Pancreatic secretion per day is 1 – 2 liters.
pH – approximately 8.0
It has
- Water
- Cations – Na, K, Ca, Mg
- Anions – HCO3, Cl, SO4, HPO4
- Digestive enzymes

4. PANCREATIC SECRETION
• Exocrine Pancreas secretes pancreatic juice.
• It has two components:
1. Pancreatic enzymes – secreted by Acinar cells.
2. Watery [aqueous] alkaline fluid rich in NaHCO3
actively secreted by duct cells that line the
pancreatic ducts.

5. PANCREATIC SECRETION
1. Pancreatic enzymes
• The pancreatic enzymes are stored in zymogen granules after they
are produced.
• They are released by exocytosis as needed.
• Pancreatic enzymes are important because they can completely
digest food, in absence of all other digestive secretions.

6. PANCREATIC SECRETION
• Pancreas Acinar cell secrete three types
of pancreatic enzymes:
1. Proteolytic enzymes for protein digestion.
2. Pancreatic amylase for carbohydrate digestion.
3. Pancreatic Lipase for fat digestion.

7. 1- Pancreatic Proteolytic enzymes
• Major Proteolytic enzymes are
- Trypsinogen
- Chymotrypsinogen
- Procarboxypeptidase
• They are secreted in INACTIVE form.
PANCREATIC SECRETION

8. How these Proteolytic enzymes are
activated?
• When Trypsinogen is secreted into the duodenal lumen
• activated to its active form TRYPSIN by Enterokinase
[enteropeptidase], an enzyme which is embedded in the mucus
membrane of duodenal mucosa.
• Trypsin once formed activates Trypsinogen [autocatalytic].
1- Pancreatic Proteolytic enzymes

10. 1- Pancreatic Proteolytic enzymes
 Chymotrypsinogen and Procarboxypeptidase.
• They are converted to active form by Trypsin in duodenal
lumen also.
IMPORTANT – We need initially Enterokinase to form
trypsin. Once trypsin is formed it carries out other
processes.

11. 1- Pancreatic Proteolytic enzymes
• Proteolytic Enzymes [Trypsin, Chymotrypsinogen,
Carboxypeptidase] attack different peptide
linkages.
• End result is formation of small peptide chains and
amino acids.

12. 2- Pancreatic amylase for carbohydrate digestion
• Pancreatic amylase causes conversion of polysaccharides
into disaccharide maltose.
• Pancreatic amylase is secreted in the Active form as it is not
the risk for auto digestion of pancreas.

13. 3-Pancreatic Lipase for fat digestion
Pancreatic lipase is very important. Why?
Because it is the only enzyme secreted throughout the
digestive system that can digest fat.
NOTE – In human, insignificant amount of lipase are
secreted in the saliva and Gastric Juice called Lingual Lipase
and Gastric Lipase.

14. 3-Pancreatic Lipase for fat digestion
• Pancreatic lipase hydrolysis dietary triglycerides
into monoglyceride and Free fatty acids, which
are absorbed in small intestine.
• Pancreatic lipase is secreted in Active form as it is
not the risk for pancreatic auto-digestion.

15. Pancreatic insufficiency
• When pancreatic enzymes are deficient, digestion of
food is incomplete.
• As pancreatic lipase is the only significant source for
fat digestion, its deficiency results in Maldigestion of
fats, it is called STEATORRHEA [increased undigested
fat in feces.
• Up to 60 – 70% of fat taken maybe excreted in feces.

16. • Digestion of protein and carbohydrate is impaired to a
lesser degree because salivary, gastric and small intestine
enzymes contribute to their digestion.

17. PANCREATIC SECRETION
2. Pancreatic Aqueous Alkaline Fluid
• As highly acidic Gastric contents are emptied into the duodenal
lumen, this acidic Chyme must be neutralized quickly in the
duodenal lumen. Why?
- Because to allow the functioning of pancreatic enzymes [they
work in neutral or slightly alkaline medium]. NaHco3 in pancreatic
fluid neutralizes the acidic Chyme.
- To prevent damage to duodenal mucosa.

18. Regulation Or Control Of Pancreatic
Exocrine Secretion
It is hormonal and neural mechanism.
1. Mainly by hormonal mechanism – secretin and
Cholecystokinin [CCK].
2. Parasympathetic stimulation – little contribution
during cephalic phase.
When Chyme enters the duodenum, Two major
hormones secretin and CCK [Entrogastrones] are released
in response to Chyme.

20. SECRETIN
• Primary stimulus for secretion of secretin is acid in the
duodenum.
• Secretin is carried by blood to the pancreas where it stimulates
the duct cells to increase NaHCO3 rich watery secretion in the
duodenum.
• NaHCO3 neutralizes the acid content of Chyme
Regulation Or Control Of Pancreatic
Exocrine Secretion

21. CHOLECYSTOKININ [CCK]
CCK is released from duodenal mucosa.
Main stimulus for release of CCK is Fat, to a lesser extent protein.
CCK is transported by blood to pancreas Acinar cell to increase
digestive enzyme secretion.
These pancreatic enzymes help to digest fat, protein and
carbohydrate.
All three types of enzymes [for protein, fat, and carbohydrate] are
packed in Zymogen granules together, therefore, all are released
together by exocytosis.
Regulation Or Control Of Pancreatic
Exocrine Secretion

24. Phases of Pancreatic Secretion
 Cephalic phase
 Gastric phase
 Intestinal phase.

25. THANK
YOU