Sources of amino acids for animals Dietary proteins are digested into amino acids in the gastrointestinal〔胃 i)tract via the action of pepsin, trypsin, chymotrypsin, carboxypeptidases and aminopeptidases
Dietary proteins are digested into amino acids in the gastrointestinal(胃 肠) tract via the action of pepsin, trypsin, chymotrypsin, carboxypeptidases and aminopeptidases. Sources of amino acids for animals
Pepsin: the first enzyme Gastric glands in discovered(18th centur) stomach linin Parietal cells (secrete HCl Chief cells (secrete pepsinogen) Stomach Gastric mucosa Pancreas pepsinogen (secretes gastrin) pepsI Pancreatic duet Exocrine cells of Da互 creas Rough ER pH Zymogen Zymogens granule active proteases Collecting duct Villi of small intestine Small o Villus Intestine. and amin Intestinal mucosa Degradation absorption (absorbs amino acids) of dietary proteins Essential amino acids
Proteins (but not pepsin) unfolded Absorbed as tri- & dipeptides, and amino acids Degradation & absorption of dietary proteins Pepsin: the first enzyme discovered (18th century). proteases Essential amino acids
Overall fate of excess amino acids Amino acids can not be stored in animals: excess being completely oxidized to release energy or converted to storable fuels(fatty acids or carbohydrates)
Amino acids can not be stored in animals: excess being completely oxidized to release energy or converted to storable fuels (fatty acids or carbohydrates). Overall fate of excess amino acids
氨的去路 第二节 Amino acid degradation 1.氧化脱氨基 氨基酸在酶的作用下脱去氨基生成相应酮酸的过 程,叫氧化脱氨基作用。 RdH分 RED R<工 A KMS M L
第二节 Amino acid degradation 1. 氧化脱氨基 氨基酸在酶的作用下脱去氨基生成相应酮酸的过 程，叫氧化脱氨基作用。 一. 氨的去路 RCHCOO —— | - NH3 + RCCOO —— - NH3 + | RCCOO+ H —— | - + O | FAD （ ）FMN FADH FMNH2 （ ）2 HO2 NH3 HO22 O2 氨基酸氧化酶
氨的去路 2.脱氢酶作用GDH / II<+)!分 TH<沙小)量 J Glu NAD(P)+h2o->a-KG+ NH4+ NADH(P)+h+
Glu + NAD(P) + H2O → a-KG + NH4 + + NADH(P) + H+ 2. 脱氢酶作用-GDH 一. 氨的去路 NH3 + | HCCOO —— - | CH2 | CH2 | COO- + NADP（）+ + HO2 NH+ 4 + + NADPH （）+ H + O | CCOO—- | CH2 | CH2 | COO- L- 谷氨酸 -α酮戊二酸 谷氨酸脱氢酶