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Metabolism of protein

Amino acid pool, Transamination, Deamination, Urea cycle, Ammonia metabolism

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Metabolism of protein

  1. 1. MetabolismMetabolism ofof ProteinProtein Dr Ifat Ara Begum Associate Professor Dept of Biochemistry Dhaka Medical College Dhaka 1
  2. 2. What is metabolism?What is metabolism? 2 Metabolism is the sum total of all the chemical reactions in the body.
  3. 3. 3
  4. 4. 4
  5. 5. Protein TurnoverProtein Turnover 5
  6. 6. 6
  7. 7. What is Amino Acid Pool?What is Amino Acid Pool? 7  The free amino acid content distributed throughout the extracellular fluid  Quantitatively, it is about 100 gm in an adult individual.  50% : Glutamate & Glutamine  10% : EAA  40% : Other AAs
  8. 8.   8
  9. 9. Intermediary metabolism of AminoIntermediary metabolism of Amino acidacid 9 Anabolism Catabolism  Synthesis of:  NEAA  Protein NPN subs Urea from NH3 via urea cycle  Glucose, glycogen  FA, fat, steroid, ketone bodies  Transamination  Deamination & removal of NH2 group as NH3  Catabolism of AA C- skeleton & synthesis of glucose, FA, steroids, ketone bodies, etc.  Oxidation of AA C- skeleton via TCA cycle
  10. 10.   10 Transamination
  11. 11. What is Transamination?What is Transamination? 11  It is the transfer of NH2 group from an AA to a keto acid with simultaneous production of a corresponding keto acid & AA respectively. Remember, No free NH3 is produced here Only transfer of NH2 group occurs
  12. 12. 12 Amino acid participating in transamination Keto acid participating in transamination All Amino acids except :  Lys  Thr  Pro Three keto acids mostly participates:  α- ketoglutarate Oxaloacetate  Pyruvate
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  15. 15. Site of TransaminationSite of Transamination 15 Cytoplasm of:  Liver  Kidney  Heart  Sk. Muscle  Brain.
  16. 16. Coenzyme needed for TransaminationCoenzyme needed for Transamination 16 Pyridoxal phosphate: Acts as an intermediate carrier of an NH2 group.
  17. 17. Importance of TransaminationImportance of Transamination 17  Funneling of NH2 group of diff AAs ultimately to α-KG : To form Glu which is the major AA that undergoes oxidative deamination.  Biosynthesis of NEAA  Formation of keto acid of an amino acid: Keto acid (carbon skeleton of AA) later on can be catabolized/oxidized
  18. 18. 18  Provides a link b/w carbohydrate, protein & fat metabolism: Because, the keto acids generated by transamination of AA can form compounds common to their metabolic cycle.
  19. 19.   19 Oxidative Deamination
  20. 20. What is Deamination?What is Deamination? 20  Removal of –NH2 group from an AA in the form of “free NH3 “ with simultaneous formation of its corresponding keto acid.
  21. 21. AA unique in the process of DeaminationAA unique in the process of Deamination 21 Glutamate Because, it undergoes rapid oxidative deamination catalyzed by Glutamate dehydrogenase (an active dehydrogenase)
  22. 22. 22
  23. 23. Site of DeaminationSite of Deamination 23 Mitochondria of:  Liver  Kidney  Heart  Sk. Muscle
  24. 24. Coenzyme needed for DeaminationCoenzyme needed for Deamination 24 NAD
  25. 25. Transamination vs. DeaminationTransamination vs. Deamination 25
  26. 26.   26 Sources & Fates of Ammonia
  27. 27. 27 Sources of NH3 Fates of NH3  Catabolism of :  Amino acid  Purine & Pyrimidine  Bacterial degradation of urea into NH3 by bacterial urease in intestinal lumen  Formation of :  Urea (Urea cycle)  Glutamate & Glutamine in liver, kidney, muscle, brain  Excretion of NH3 with urine as NH4+ salt
  28. 28. 28 Glutamine : The temporary non-toxic storage & transport form of NH3. NH3 + α-KG  Glutamate Glutamate + NH3  Glutamine
  29. 29. Ammonia IntoxicationAmmonia Intoxication 29
  30. 30.   30 Urea cycle
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  32. 32. 32
  33. 33. Nitrogen BalanceNitrogen Balance 33
  34. 34. Inborn error of protein metabolismInborn error of protein metabolism 34  Alkaptonuria  Homocystinuria  Phenylketonuria  Albinism  Maple syrup urine disease
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Amino acid pool, Transamination, Deamination, Urea cycle, Ammonia metabolism

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