未被消化的蛋白质

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1、Metabolismofprotein&aminoacids1A.Thephysiological&nutritiousfunctionofproteins2nitrogenbalance&proteinrequirement31.nitrogenbalancea.conceptb.experiment4c.3conditionsnitrogenequilibriumnegativenitrogenbalancepositivenitrogenbalance52.minimalrequirementsofprote

2、in3.essentialaminoacidsandtheirbiologicalvalue67anindicatortovaluatethenutritionalvalueoftheproteinsbiologicalvalue84.ComplementaryfunctionofproteinsB.Digestion,absorption,&putrefactionofproteins9dietproteinaminoacidsdigestionProteolyticenzymea.digestion10b.ab

3、sorptionsitemechanismcharacteristics111213c.putrefactionconcept14未被消化的蛋白质,未被吸收的氨基酸，肽largeintestinebacteriasDecarboxylationdeamination有毒；amine,H2Sindolehydroxybenzene、ammonia（NH3)、other：CO2,CH4NutrimentFattyacid、vitAbsorptioninintestineexcretebloodliver15•decar

4、boxylation•reductive&deamination161718•thesourcesofammoniaintheintestine19bloodinfiltrateintestinekidneyexcrete（20g）NH2-CO-NH2liverNH3(25%)7gNH2-CO-NH2urease(bacterias)2NH3+CO2（4g）importancesourcesofbloodammonia------absorptedfromintestine20C.generalmetabolism

5、ofaminoacids1.Sketchplan2122DietaryproteinTissueproteinaminationofα—ketoacidsdegradationSynthesis85%NonessentialA.ADigest,absorptiondeaminationaminesNH3α—ketoacidsoxidationGlucose,fatsN.EAAdecarboxylationAminoacidmetabolicpoolureaothersubstances232.deamination

6、ofaminoacidsa.oxidativedeamination1)reaction24252)enzymes•L-aminoacidoxidase•D-aminoacidoxidase•L-glutamatedehydrogenase2627•characteristicsb.transamination1)reaction28292)importanttransaminationsystem.30glutamicpyruvictransaminationsystem（glutamicpyruvictrans

7、aminase,GPT）（alaninetransaminase,ALT）glutamicoxaloacetictransaminationsysten:（glutamicoxaloacetictransaminase,,GOT）（aspartatetransaminase,AST)31NH2OONH2Glu丙酮酸α—酮戊二酸AlaNH2CO-COOHOCH-COOHNH2Glu草酰乙酸α—酮戊二酸ASPCOOH-(CH2)2-CH-COOH+CH3-C-COOHCOOH-(CH2)2-C-COOH+CH3-CH-

8、COOHCOOH-(CH2)2-CH-COOH+CH2COOHCOOH-(CH2)2-C-COOH+CH2-COOHALTAST322)enzyme&coenzyme333435biologicalsignificance&characteristics36c.combineddeamination1)reaction373839402)biological