digestion_of_proteins [2].pptx biochemistry

biochemistry ppt

1. DIGESTION OF PROTEINS BY: HOPE SHRUTI PETER

2. INTRODUCTIOIN Digestion is a process involving the hydrolysis of large and complex organic molecules of foodstuffs into smaller and preferably water-soluble molecules which can be easily absorbed by the gastrointestinal tract for utilization by the organic Proteins are too large to be absorbed. The dietary proteins are hydrolyzed to amino acids by proteolytic enzymes, which can be easily absorbed. Proteolytic enzymes responsible for degrading proteins are produced by three different organs; The stomach, pancreas and the small intestine.

3. DIGESTION OF PROTEINS IN THE MOUTH No digestion of protein in mouth.
No proteolytic enzymes present in the saliva. Function of the saliva – lubricate the food, this helps in making food soluble for the action of proteolytic enzymes. After mastication and chewing, the bolus of food enters the stomach where it is acted upon by gastric juice.

4. DIGESTION IN STOMACH Digestion of protein starts in stomach. When proteins enters the stomach, it stimulates the secretion of the hormone gastrin, from gastric mucosal cells. Gastric juice contains many proteolytic enzyme. NAMELY Pepsin Rennin Gastricsin Gelatine

5. PEPSIN It is a potent proenzyme and is present in gastric juices of different species including the mammals. It is secreted in an inactive zymogen form as pepsinogen. Pepsinogen is hydrolyzed in the stomach by hydrochloric acid to form active pepsin. Pepsin has an optimum temperature of 1.6 to 2.5

6. Continuation on pepsin… ACTION ON MILK Pepsin can act on milk It hydrolyses the soluble phosphoprotein casein in milk to produce paracasein and a protease.

7. ACTION OF RENINN Reninn is absent in adult humans In the calf, it is secreted in zymogen form as prorenin, which is activated in the stomach to form active reninn .

8. GASTRICIN Gastricin is an enzyme secreted in the gastric juice of human as inactive zymogen form, which is activated in presence of HIC. pH is 3 to 4. It acts as a proteinase It requires acidic medium for its activity

9. DIGESTION OF PROTEINS IN THE INTESTINE The luminal surface of intestinal epithelial cells contains aminopeptidases and dipeptidases . Aminopeptidase is a non-specific exopeptidase which repeatedly cleaves N-terminal aminoacids one by one to produce free amino acids and smaller peptides. The dipeptidases act on different dipeptides to liberate amino acids

10. DIGESTION IN DUODENUM After mastification the bolus goes to the duodenum where meets with pancreatic juice. CHIEF ENZYMES IN THE PANCREATIC JUICE Trypsin Chymotrypsin Carboxyl peptidate Ellastases collagenase

11. TRYPSIN Trypsin is secreted in an inactive form trypsinogen, which is converted to form active trypsin. ACTIVATION IS BROUGHT BY: Enterokinase of intestinal juice at a pH of 5.5 Autocatalytically at a pH of 7.9 Ca 2 ions

12. CHYMOTRYPSIN Chymotrypsin, a proteinase is secreted as inactive zymogen chymotrypsinogen Chymotrypsinogen is converted to chymotrypsin by trypsin.

13. DIGESTION IN SMALL INTESTINE PROTEOLYTIC ENZYME IN SMALL INTESTIN Enterokinase Amino peptidase Prolidase Tri and di peptidase

14. ENTEROKINASE Also known as enteropeptidase . A glycoprotein enzyme which is present in epithelial cells of brush boarders of duodenal mucosa and secreted in the duodenum. ACTION It hydrolysis trypsinogen using 2 calcium ions into active trypsin

15. AMINO PEPTIDASE Can hydrolyse peptides to tripeptides Cannot hydrolyse dipeptide to tripeptidase TRI AND DI PEPTIDASES These enzymes hydrolyse the peptide at two places: In the microvilli membrane of intestinal epithelial cells or inside the epithelial cells after the peptidase have been absorbed inside the cell. Tripeptidase acts on tripeptide to produce a dipeptide with free amino acid

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