chapter 11 catabolism of protein 第十一章 蛋白质分解代谢
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Chapter 11 Catabolism of Protein 第十一章 蛋白质分解代谢. 主要内容. 第一节 蛋白质的营养作用 第二节 蛋白质的消化、吸收、腐败 第三节 氨基酸的一般代谢 第四节 一些氨基酸的特殊代谢. 目 的 和 要 求. 一、了解 protein 的营养作用、消化、吸 收和腐败 putrefaction 过程 二、 掌握 AA 的脱氨基作用 deamination , 氨 ammonia 的转运 三、 掌握尿素 urea 的合成 四、 了解 α- 酮酸的代谢和 AA 的脱羧基作 - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 11 Catabolism of Protein
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protein putrefactionAAdeamination ammoniaurea-AA decarboxylationone carbon unit AA
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Proteinp291 23
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nitrogen balance 1 Total N Balance
2Positive N Balance
3Negative N Balance # concept of nitrogen balance:
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Protein 3050g - Total N Balance 7080g 1.05g/Kg
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300-500400--500100-200125-200(5050-10025-50),1005025
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10030077(150:1)2.41
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Definition: proteinEAA classcontentproportion EAAIleMetValLeuTrpPheThrLys NEAA semi-essential AA/conditionally essential AA ArgHis
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15.6 16.6 36.3 28.2 () 16.7 19.1 21.3 50.5 15.5 26.4 26.2 18.9 15.4 () 20.3 () 17.3 17.0 2l 2 21.5 18.2 16.5 () 76.5 14.7 16.4 100
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EAAmg/kg
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(Physiological Value of Protein):
(Protein Complementarity):
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pepsin trypsinchymotrypsin elastasecarboxypeptidase A/B enterokinaseaminopeptidase dipeptidase
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PH 8.0~9.0 8.0~9.0 8.8 A 7.4 B 8.0
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peptideAla5, Lys1, Phe124-DNFBpeptideproteinN-terminal AADNFB-AlatrypsintripeptideLys1 Ala2tetrapeptideAla3 Phe1peptidechymotrypsinhexapeptideAApeptideprimary structure
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95%protein oligopeptide dipeptide AA
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carrier proteinVarious AA carrier proteins nonpolar AA carriers basic AA carriers: acidic AA carriers sub-AA and Gly carriersProGly
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Absorption of dipeptides and tripeptides
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glutamyl cycle - GSH
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- GSH
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protein NH3R-CH2-COOHCO2R-CH2-NH2hydroxybenzenes, indoles, H2S, CH4
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Dietary proteinTissue protein amination of -keto acidsdegradation Synthesis 85% NEAA Digest,absorptiondeaminationamines NH3 -keto acidsoxidation Glucose, fatsNEAAdecarboxylationAA metabolic poolurea other active substancesSummary of AA Catabolismspecifically
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# leading pathway of AA degradation1. transaminaton
2. oxidative deamination
3. transdeamination
4. purine nucleotide cycle AAammonia-keto acid
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1. Alanine Aminotransferase, ALT or Glutamate-pyruvate Transferase, GPT Aspartate Aminotransferase, AST or Glutamate-oxaloacetate Transferase, GOT
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Clinical roles of detecting ALT and AST:
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Enzymes: L-amino acid oxidase D-amino acid oxidase L-glutamate dehydrogenase(GDH)
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GDH
Glu
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Biological roles AA
NEAA
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Purine Nucleotide Cycle
- Gln (kidney)Blood Ammonia
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Ammonia Absorption: NH3 NH4+H+OH- NH3NH4+NH3NH4+pHpH6NH3pH6 ammonia
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Transportation of AmmoniaWhy
How to transport
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GlutaminaseH2O+NH3Gln synthetaseATPADP+Pi1Ammonia Carrying by Gln:
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ammoniaGlnammoniaureaammoniaH+NH4+Glnammonia ammonia
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2Alanine-glucose Cycle
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Roles eliminating toxicity of ammonia
supplying energy for muscle
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Synthesis of Urea /Ornithine Cycle /Urea Cycle /Krebs-Henseleit Cycle1932, , Krebsammonia(>80%
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1.Process of Urea Synthesis
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Total Reaction Formula:
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2. Biological functions of Urea Cycle:Thorough removal of ammonia
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3. Summary of Urea Cycle:1 urea:2NH3,1CO2,3ATP1NH3AANH3,NH3AspUreaammoniaNPNureaammoniaAAureaNPNCPS-CPS-
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CPS CPS
Site mitochondria cytosol N source NH3 Gln Products urea pyrimidine CPS : carbomoyl phosphate synthetase
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3. High blood ammonia & Ammonia poisoning
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Metabolism of -keto acidsaminationtransamination conversionoxidation
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Glucogenic AA and Ketogenic AA
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CoA -CoAPEP-CoACO2CO2T A C
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Leu
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Lys
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DecarboxylationAAdecarboxylaseamine+CO2()
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Common important amines:Glu-amino butyric acidGABATry5-hydroxy tryptamine5-HTHishistamineCystaurineOrn and Metpolyamines
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1GABA
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25-HT5-5-HT
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3 Histamine
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4catecholamines CH2CHNH2COOHCH2CHNH2COOHOHCH2CHNH2
CH2NH2 HCOH CH2NH-CH3 HCOH
OHOH
OH OH
OH OH OHOH
DOPADOPA CO2---N--CH3
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5Taurine
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6Polyamines
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Metabolism of individual AA
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one carbon unit sulfur-containing AA aromatic AA branched chain AA
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Conceptsome AA one carbon groupsClasses -CH3 -CH2- -CH= -HC=O -CH=NH Carrier tetrahydrofolate (FH4) FH4N5N10One Carbon Unit(OCU)
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Formation and structure of FH4Sites binding OCU
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OCUFH4
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OCU generation & conversion
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Biological functions of OCU metabolism: OCU OCU OCUAA
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Sulfur-containing AAClassesMet/Cyscysteine Cystine
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Metabolism of Met+
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1Met cycleRHR-CH3VitB12CH3-:
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OCU generation & conversion
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2Biological roles: CH3 FH4
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B12folate
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Metabolism of Cys and CystineCystineCysTaurine + NH3 + H2SH2SO43--5-PAPSGSHconversion
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1Conversion of Cys and Cystine Cys Cystine
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2Cysactive H2SO4
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3CysGSHenzymesproteins
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Aromatic AA (AAA)Classes of AAAPheTyr Trp
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Phe & Tyr:Phe Tyr
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Phe transforming into Tyr
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(phenyl ketonuria, PKU)Phe Tyr transaminationPKU,
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PKU60%
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Tyr Tyr
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Tyrmelanin
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TyrDOPADANEE
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Parkinsons disease DA60 601.71.6400170 1997411
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Tyr
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Summary of Phe & Tyr metabolism
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Trp: 5-HTCOUA
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Branched chain AA
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PKU
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CoA -CoAPEP-CoACO2CO2T A C
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AA metabolic poolDietary proteinTissue proteinNEAATissue protein-AmineN
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2Alanine-glucose Cycle