Digestion protein, absorption amino acid and amino acid pool
•
55 recomendaciones•11,659 vistas
Biochemistry from Dr. Dhiraj J Trivedi SDM College of Medical Sciences and Hospital, Dharwad, India
Recomendados
Más contenido relacionado
La actualidad más candente
La actualidad más candente (20)
Similar a Digestion protein, absorption amino acid and amino acid pool
Similar a Digestion protein, absorption amino acid and amino acid pool (20)
Más de Dhiraj Trivedi
Más de Dhiraj Trivedi (20)
Último
Último (20)
Digestion protein, absorption amino acid and amino acid pool
- 1. Protein metabolism Live with intention ….. The best within you Is waiting to be explored
- 2. Why to study protein metabolism? • Most serious nutritional problem in world. 63% Indians malnourished? • Affected groups • Pregnant and lactating women • New born and growing children • Poor and aged persons • Person habitually avoiding protein rich food
- 3. Dietary proteins • Contains simple and conjugated proteins • Primary source of nitrogen to the body • 16 gm protein nitrogen is excreted/day in health • About 70 to 100 gm of proteins are required per day by adult to replace loss. • Regular supply necessary for cell integrity, growth and cellular functions. (Nitrogen balance)
- 4. Name major functions performed by dietary proteins. • Performs four basic functions 1. Synthesis of body proteins 300 to 400gm/ day 2. Oxidised to supply energy 30 to 50 gm/day 3. Required for nitrogenous compound synthesis 4. Source of non- nitrogenous substances (Glu, FA)
- 5. What is peptidase? Or proteolytic enzymes? • Hydrolase group of enzymes that hydrolyse (digest) proteins are called peptidase or proteolytic enzymes or protease . • Two Type 1. Endopeptidase 2. Exopeptidase
- 6. Why digestion of proteins? How? • Proteins can not be absorbed as such. • Hence need digestion by proteolytic enzymes. • Cooking denatures proteins and make them more digestible, palatable and tasteful. • Complex molecules of proteins are digested to simple amino acids before absorbed.
- 7. Name proteins that resist digestion? • Group of proteins called scleroproteins resist digestion. • Hair, Nail, Hoof & Bone proteins can not be digested
- 8. Name the types of proteolytic enzymes. Proteolytic enzymes are of two types Endopeptidase Exopeptidase Act in the interior of proteins Act on the periphery of the protein molecule Cleaves internal peptide bonds Cleaves terminal peptide bonds End product – Small peptides, End product – free amino acids and dipeptides Eg. Pepsin, Rennin, Trypsin, Chymotrypsin, Elastase Eg. Carboxypeptidase, Aminopeptidase
- 9. Give examples of Endopeptidase & their specificity. Enzyme Origin Specificity Pepsin Chief cells / Stomach Aromatic amino acids and acidic amino acids Trypsin Pancreatic juice Basic amino acids Lysine and Arginine Chymotrypsin Pancreatic juice Aromatic amino acids and Leu, Arg, Met, His Elastase Pancreatic juice Glycine, Serine, Alanine
- 10. Digestion of protein No digestion in mouth Due to lack of proteolytic enzymes in saliva
- 11. In stomach - HCl • Vegal stimulus and Gastrin --- secrete HCl • 2000 – 3000 ml / day • Act on native and cooked protein • End product Metaprotein, Coagulated protein Digestion of protein
- 12. Digestion of protein • Secreted as pepsinogen (inactive form) • Activated by HCl and Pepsin itself (Autocatalysis) • Optimum pH 2.0 • Act on peptide bonds formed by carbonyl group of aromatic and acidic amino acids in proteins • End product Proteoses and peptones In stomach - by Pepsin
- 13. Pepsinogen Pepsin [H + ] Pro enzyme Chief cells ActiveAutocatalysis Act on aromatic amino acid P T T and acidic amino acids A G In stomach - by Pepsin
- 14. Digestion of protein by pepsin how much essential? • It is important but not essential • Gastroctomy person can maintain proper nitrogen balance.
- 15. Digestion of protein • Secreted only in infants and child age, Absent in adult. • Optimum pH 4.0 – 4.5 • Act on milk protein casein • End product Para casein which is further acted upon by pepsin for digestion In stomach - by Rennin
- 16. Milk Casein Para casein [Rennin , Ca2+] Acted up on by pepsin Curdling Help to keep milk in stomach for long time Ensures complete digestion In stomach - by Rennin
- 17. Digestion of protein In duodenum Acidic chyme stimulates secretion of Secretin and pancreozymin Which in turn stimulates pouring of pancreatic juice Pancreatic juice contains • Trypsinogen • Chymotrypsinogen • Pro-Elastase • Pro carboxy peptidase • Por-Collagenase
- 18. Activation of pancreatic peptidases Trypsinogen Trypsin [Enterokinase] Pro enzyme ActiveAutocatalysis Chymotrypsinogen Chymotrypsin [Enterokinase, Trypsin ] Pro Carboxy peptidase Carboxy peptidase
- 19. Action of pancreatic enzymes on protein Enzyme Specificity Trypsin Basic amino acids Lysine and Arginine Chymotrypsin Aromatic amino acids and Leu, Arg, Met, His Elastase Glycine, Serine, Alanine Carboxy peptidase Act on C terminal peptide bonds End product Dipeptides, Tripeptides and free amino
- 20. Digestion of protein In small intestine Intestinal mucosal cell produces Amino peptidase , dipeptidases and tripeptidases. Amino peptidase act on N terminal peptide bonds of protein And dipeptidases act on Dipeptides End product is Free amino acids
- 21. Dietary Protein Denatured Protein Metaprotein Proteose and Peptones Small peptides Di and tri peptides Amino acids Cooking HCl Trypsin Chymotrypsin Elastase Pepsin Carboxy peptidase Amino peptidase Dipeptidases Tripeptidases Digestion of protein
- 22. Absorption of amino acids • Only amino acids are absorbed • Intestinal epithelial cell & renal tubular cell • Carrier system exists or • By Secondary active transport • Genetic defect -- improper absorption of particular amino acid (Hartnup’s disease, Glycinuria)
- 23. Absorption of amino acids Three mechanism exists 1. Sodium independent facilitated transport system 2. Sodium dependent secondary active transport system 3. γ- Glutamyl cycle (meister cycle)
- 24. Mechanism of amino acid absorption Sodium independent facilitated transport Purely on concentration gradient
- 25. ATP ADP Active transport Secondary active Mechanism of amino acid absorption Sodium dependent Secondary active transport
- 26. γ- Glutamyl cycle (meister cycle) Operates in small intestine Requires glutathione (γ - glutamyl cysteinyl glycine ) Energy expenditure is large
- 27. γ- Glutamyl cycle (meister cycle) Amino acids Glutathione Glutamyl transferase Cystenyl Glycine Glutamyl AA Gutamate γ -Glutamyl cysteine Glycine ATP ATP A D P + Pi A D P + Pi 1 2 3 4 5 ATP A D P + Pi Amino acids 6 7
- 28. Some Exceptions • In case of infants direct absorption of IgA from the mothers milk (Colostrum) • This provides passive immunity to the • newborn 1. Some plant proteins are endocytosed in partially digested form • Basis of allergens and anaphylactic reactions Carrier proteins defect 2. Hartnup disorder 3. Amino acidurias