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Hormonal regulation of proteins metabolism

During digestion, proteins are hydrolyzed into amino acids. Amino acids are absorbed by the capillaries of villi and enter the liver via the hepatic portal vein.

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Hormonal regulation of proteins metabolism

  1. 1. Protein and amino acids metabolism Types of amino acids Digestion of protein Metabolism fates of amino acids Hormonal regulataion of protein metabolism 
  2. 2. Protein and amino acids metabolism Metabolism of proteins is the metabolism of amino acids. Metabolism of amino acids is a part of the nitrogen metabolism in body. Nitrogen enters the body in dietary protein.  Dietary proteins cannot be stored as such but used for formation of tissue proteins due to there is a continuous breakdown of endogenous tissue proteins. Total chemical reactions taking place in side the body of organism and it is divided into two types catabolism and anabolism
  3. 3. During digestion, proteins are hydrolyzed into amino acids. Amino acids are absorbed by the capillaries of villi and enter the liver via the hepatic portal vein.
  4. 4. Essential amino acids Lysine, Leucine , Isoleucine, Valine, Methionine, Phenylalanine, Threonine, Tryptophan Nonessential amino acids Alanine, glycine, , aspartate , glutamate, serine, tyrosine, cysteine , proline, glutamine, aspargine  For formation of new tissue protein : all essential amino acids that can not be synthesized by organism & provided by dietary protein must be present at the same time with nonessential amino acids that can be synthesized by organism . Types of amino acids
  5. 5. Digestion of protein Proteins are broken down by hydrolyases ( peptidases or proteases ) : • Endopeptidases : attack internal bonds and liberate large peptide fragments ( pepsin trypsin Chmotrypsin & Elastase ) • Exopeptidases : remove one amino acid at a time from - COOH or -NH2 terminus (amino peptidase & carboxypeptidase).  Endopeptidases are important for initial breakdown of long polypeptides into smaller ones which then attacked by exopeptidases.  Digestion of protein can be divided into : a gastric , pancreatic and intestinal phases.
  6. 6. Pepsinogen Pepsin HCL ProteinAmino acid+Oligopeptides & polypeptides
  7. 7.  This phase ends with free amino acids and small peptides of 2-8 amino acid residues which account for 60% of protein digestion. • Intestinal enzymes are: aminopeptidases (attack peptide bond next to amino terminal of polypeptide) & dipeptidase . • The end product is free amino acids dipeptides & tripeptides.
  8. 8. Amino acids Construction Synthetic proteins, hemoglobin, enzymes Removal amino Ketone acids + [NH3] Ammonia Urea Fats Pyruvate acid Acetyl - CoA Glutaric acid Krebs cycle
  9. 9. Transport and fate of amino acids and protein in liver & muscle muscle Alanine plays a special role in transporting amino groups to liver. Ala is the carrier of ammonia and of the carbon skeleton of pyruvate from muscle to liver. The ammonia is excreted and the pyruvate is used to produce glucose, which is returned to the muscle. Glutaminase reaction releases NH3 that enters the urea cycle in the liver (in the kidney, it is excreted into the urine)
  10. 10. Metabolism fates of amino acids 1- Body protein biosynthesis . 2- Small peptide biosynthesis . 3- Synthesis of non-protein nitrogenous (NPN)) compounds (creatine, Urea, ammonia and uric acid 4- Deamination & Transamination to synthesized a new amino acid or glucose or ketone bodies or produce energy in starvation.
  11. 11. Insulin is the primary anabolic hormone Glucagon and cortisol are catabolic hormones Trigger the breakdown of body protein for energy Hormonal regulatation of protein metabolism
  12. 12. • Alters phosphorylation of many key intracellular metabolic enzymes (minutes) • Alters protein synthesis and gene transcription (hours)
  13. 13.  Promotes • Transport of amino acids • Protein synthesis • Gene transcription  Inhibits protein degradation  Prevents glucose synthesis in liver  Preserves amino acids  Lack of insulin causes elimination of protein stores
  14. 14. Prevents hypoglycemia Increases glucose synthesis from amino acids Increases with exercise independent of blood glucose Effects of Glucagon
  15. 15. Cortisol Cortisol is produced by adrenal glands cortisol affects metabolism by stimulates protein degradation in muscles while it activates proteins synthesis in liver tissues
  16. 16. Growth hormone is increasing transport of amino acids to muscle tissues to synthesis protein Growth hormone stimulates protein anabolism in many tissues. This effect reflects increased amino acid uptake, increased protein synthesis and decreased oxidation of proteins Growth hormone
  17. 17. REFERENCES  www.morgan HE, Earl DCN, Broadus A, Wolpert EB, Giger KE, Jefferson LS. Regulation of protein synthesis in heart muscle. I. Effect of amino acid levels on protein synthesis. J Biol Chem. 1971;246:2152–62. Abstract/FREE Full Text  www.Proud CG, Denton RM. Molecular mechanisms for the control of translation by insulin. Biochem J. 1997;328:329–41.  Mendez R, Welsh G, Kleijn M, Myers MG, White MF, Proud CG, Rhoads RE. Regulation of protein synthesis by insulin through IRS-1. Prog Mol Subcell Biol. 2001;26:49–93. Medline  Liu Z, Wu Y, Nicklas EW, Jahn LA, Price WJ, Barrett EJ. Unlike insulin, amino acids stimulate p70S6K but not GSK-3 or glycogen synthase in human skeletal muscle. Am J Physiol Endocrinol Metab. 2004;286:E523– 528. Abstract/FREE Full Text  Fryburg DA, Jahn LA, Hill SA, Oliveras DM, Barrett EJ. Insulin and insulin- like growth factor-I enhance human skeletal muscle protein anabolism during hyperaminoacidemia by different mechanisms.

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