On an average, about 1.2 to 1.5 liters of pancreatic juice is released daily in our duodenum in the digestive juices released under the process of digestion in the small intestine. It is a water-like thin, colorless and, due to sodium bicarbonate, highly alkaline (alkaline pH—7.5 to 8.3) liquid.
Therefore, when the chyme reaches the duodenum, the pancreatic juice neutralises the acidity of the chyme and inactivates the pepsin of the gastric juice present in it. This juice contains 96% water and remaining salts and digestive enzymes. It has been called a complete digestive juice because it contains the following enzymes that digest all types of macronutrients—proteins, carbohydrates, lipids, and nucleic acids—in an alkaline medium.
1. Pancreatic Amylase or Amylopsin : Like salivary amylase enzyme, it breaks down chyme starch, glycogen and other polysaccharides (except cellulose) into disaccharide sugar called maltose.
(C6H10O5)2n + nH2O (C12H22O11)n
2. Pancreatic Lipase or Steapsin : The main credit for the digestion of lipids of food goes to this enzyme. Normally 90 to 95% of the lipids in the food are digested. The remaining lipids are passed out in the faeces undigested. In this digestion, lipase enzyme reacts with the droplets of fats emulsified by bile to break down the fat molecules into monoglycerides and fatty acids. With the help of a protein called colipase present in the pancreatic juice, lipase is able to reach the fat cells and react with them.
3. Pancreatic Esterase : Cholesterol in food is mainly in the form of cholesteryl esters. Esterase enzyme breaks down these esters and separates cholesterol from them.
4. Phospholipase : It separates fatty acids from phospholipids.
5. Endopeptidases : Pancreatic juice, like pepsin of gastric juice, contains two proteolytic enzymes-trypsin and chymotrypsin. They break down the remaining complex proteins of the chyme and peptones, proteoses and large polypeptide chains into smaller polypeptide chains.
6. Carboxypeptidase : It is a zinc containing exopeptidase which hydrolyzes the carboxyl terminal bonds of polypeptide chains to break them into amino acid monomers.
7. Nucleases: Pancreatic juice also contains enzymes called deoxyribonuclease and ribonuclease to digest nucleic acids (DNA and RNA) which break down these acids into their constituent nucleotides and then break these nucleotides into nucleosides and phosphates.
Pancreatitis : Pancreas is damaged by excessive drinking, obstruction of pancreatic duct, cancer, virus infection, etc., or trypsin enzyme becomes active in the pancreas itself and digests its tissue and lyses it. All these conditions are called pancreatitis.
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