12Metabolism of Protein and Amino Acid Part 1
12、Metabolism of Protein and Amino Acid Part 1 Nutrition of Protein 一、Nitrogen Balance 正常成人pr分解代谢水平: 总 400 g: 300 g循环,100 g消耗(产能排泄), 外源补充 Site: 组织内250 g,消化道 150 g 成人分解pr主体:内源蛋白组织内分解 1
Protein Synthesis from food in vivo Resource Protein in vivo 氨基酸代谢库 Amino acid pool NH 3 Fate Ammonia α-Ketoacid ies od ob et K Glu co se En er gy CO 2 Urea Amines (胺) Substance with nitrogen 3
Nitrogen Balance- 摄入氮量和排除氮量的关系 All Nitrogen Balance- 摄入氮量=排除氮量 In=Out Positive Nitrogen Balance- 摄入氮量>排除氮量 In>Out Negative Nitrogen Balance- 摄入氮量<排除氮量 In<Out 4
二、Essential , Non-Essential and Semi-Essential Amino Acids 8 EAALys Trp Val Leu Ile Thr Met Phe Two SEAAHis Arg 5
“High Quality” Protein * 6
常见蛋白酶: • Trypsin • Chymotrypsin • Pepsin • 嗜热菌蛋白酶(Thermolysin) • 羧肽酶(Carboxypeptidase) • 氨肽酶(Aminopeptidase) 7
Chymotrypsin 糜 蛋 白 酶 水解位点 Peptide Chain R 1=Phe, Trp, Tyr时 水解快; R 1= Leu,Met 和His水解稍慢。 R 2=Pro 水解受抑。 10
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Active Site cut at Lys, Arg Deep and negatively charged pocket O O –C–N–C–C–N– C C NH 3 + COOC Asp Chymotrypsin cut at Trp, Phe, Tyr O O –C–N–C–C–N– C Elastase cut at Ala, Gly O O –C–N–C–C–N– CH 3 Shallow and non-polar pocket Non-polar pocket 13 Juang RH (2004) BCbasics Trypsin
Part 2 Degradation, Absorption, Putrefaction and Detoxification of Proteins 只能成为Free Aa,少量二肽,三肽才能吸收。 (一)Degradation(分解,消化) Pepsin Food Pr Stomach(胃) Small peptides peptide fragment Trypsin、Chymotypsin、 Elastase Duodenum (十二指肠) Carboxypeptidase B、A (十二指肠) 16
Oligo-peptides Aminopeptidase Aa, Bipeptide and tripeptide etc Dipeptidase, Tripeptidase (肠粘膜细胞) Free Aa (消化道各种酶的 协同作用产生) Papain, Bromelain(菠萝蛋白酶) Ficin (无花果蛋白酶)etc in Plant 17
physiological detoxification (解毒) 腐败产物大多有毒, 大部分可直接排除体外, 少 数由肝脏酶作用而解毒后, 排除体外。 detoxification ways: ◇Oxidative detoxification (Specific enzyme) ◇Conjugated detoxification (毒素+无毒物) 24
Part 3 Common Metabolism of Aa 一、 Deamination of AA Aa失去-NH 2的作用称为脱氨基作用 ◆ Oxidative Deamination ◆ Transamination ◆ 联合脱氨(Transdeamination) ◆ Nonoxidative deamination 25
★ Oxidative Deamination -AA在酶作用下,氧化成 -酮酸,同时消耗氧并产生 氨的过程。 反应通式: - H AA oxidase R-C-COOH+H 2 O 2+NH 3 +O +H O R-C-COOH 2 2 O NH 2 - - AA H oxidase R-C-COO- H 2 O R-C-COOH + NH 3 NH 2 FP FPH 2 NH 2 O 26 FPH 2+O 2 FP+H 2 O 2 -
1、 FAD or FMN为辅酶或辅基的脱氢酶类 (黄素酶) 受氢体不同分为 2类: ⑴需氧黄(素)酶(Aerobic flavoenzyme) 氧为直接受氢体,2 H+O 2 H 2 O 2 S-2 H 2 H ---- FMN or FAD H 2 O 2 需氧黄酶 S ---2 H FMNH 2 or FADH 2 O 2 (已氧化代谢物) e. g. Amino acid oxidase or Amino acid DHase 27
★Transamination[转氨作用] α-Aa与α-ketoacid之间-NH 2转移作用,一种 脱氨形式。 Glu Pyruvate GPT[谷丙转氨酶] α-ketoglutarate (α-k. G) Ala 32
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Transaminations Gln + Pyruvate Glu + OAA Glutamate-Pyruvate Aminotransferase (GPT in liver) α-KG + Ala Glutamate-Oxaloacetate α-KG Aminotransferase + Asp (GOT in muscle) 40
NH 2 Asp NH 2 α-AA IMP α-KG NH 2 腺苷酸代 GPT α -K eto ac id 腺苷酸 脱氨酶 琥珀酸 GOT Glu NH 2 NH 3 H 2 O OAA AMP Fumarate NH 2 Malate 49
★Nonoxidative deamination (多在微生物中) 包括: Direct deamination Dehydrated deamination; Desulfurated hydrogen deamination Hydrolyze deamination Reducing deamination. 53
二、Decarboxylation脱 羧 基 作 用 AA 专一性 强 脱羧酶 胺类化合物 (PLP) - - 醛亚胺 CO 2 - - - R 1 H H-C-N= C H R 2 - - - H 2 O - - R 1 H H-C-NH 2 + O=C H R 2 一级胺 PLP R 1 H ︱ H-C-N= C + H 2 O ︱ ︱ COOH R 2 - - R 1 H H-C-NH 2 + O=C COOH R 2 PLP 56
a. 一级胺 R-CH 2 -NH 2 + O 2 + H 2 O 胺氧化酶 (解毒过程) NH 3+H 2 O 2 R-CHO R-COOH Metabolism of Lipid 58
Part 4 Metabolism of Deamination Product of AA Products: α-ketoacid Ammonium(NH 3) 60
Ala-Glc cycle PROTEIN MUSCLE Muscle Glc AA NH 3 Glu -KG Pyr Ala Liver Blood | Glc | | | | | Ala | | Glc | | | Pyr | | Ala | Urea NH 33 NH Glu -KG 66
2、Gln转运氨 Glu + NH 3 Glutamine synthetase 谷氨酰胺合成酶 Gln (B loo dc yc le) (Brain, muscle etc) Gln 谷氨酰胺酶 Glutaminase Glu + NH 3 (Liver, kidney) 69
尿素循环(Ornithine Cycle,in liver) 1、Process(liver cell Mit) a. 氨甲酰- 合成 氨甲酰磷酸合成酶-I CO 2 + NH 4+ + H 2 O (Mit) HCO 3 - + Gln (Cytosol) 氨基甲酰磷酸合成酶II b. 瓜氨酸(Cit)合成 NH 2 -CO 2 ADP + Pi 2 ATP NH 4+的活化 NH 2 -CO 2 ADP + Pi Orn转氨甲酰基酶 +鸟氨酸(Orn) + Glu CTP 72 瓜氨酸
2. Process in cytosol 瓜氨酸出Mit 瓜氨酸 + Asp 精氨酰琥珀酸合成酶 ATP 精氨酰琥珀酸 AMP + PPi 精氨酰琥珀酸裂合酶 Arg + Fumarate Arg, H 2 O 鸟氨酸 NH 2 -CO-NH 2 (Urea) Malate OAA Asp 73
1、生成Aa α- keto acid Amination NEAA(非必需氨基酸) 2、氧化成CO 2和H 2 O Pyruvate、OAA 、α-ketoglutarate TCA Cycle 3、转变为FA和Sugar Glucogenic Aa (All non-essential Aa,13/14) Ketogenic Aa (Lys ? , Leu) Glucogenic with Ketogenic Aa (Ile、Lys、Phe、Trp、 Tyr,5)即 异赖 3芳 如Ala、Ser、Cys也可形成Ac. Co. A OAA, 生糖Aa和生酮Aa的界定并非严格 81
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二、Catabolism of Gly and Ser PYRU VATE TCA CYCLE Gly 甘氨酸代谢途径 88
三、 Catabolism of Met ,Cys. H and Cys ATP Met PPi + Pi CH 3 S-腺苷 Met FH 4 同型Cys N 5 -CH 3 -FH 4 S-腺苷同型Cys 腺苷 (高Cys) Propionyl Co. A Succinyly Co. A TCA CYCLE 89
Phenylketonuria (PKU) Disease 苯丙酮尿症 • Deficiency of Phe hydroxylase • Occurs in 1: 16, 000 live births in U. S. • Seizures, mental retardation, brain damage • Treatment: ? ? • Screening of all newborns mandated in all states Tyr Phe Transamination Phenylpyruvate (urine) 92
Tryptophan Metabolism: Serotonin Formation Indole ring hy T dr rp ox yl as O 2 e Tryptophan (Trp) 5 -Hydroxy-tryptophan e s la CO 2 b r a y x o D ec 5 -Hydroxy. Tryptamine (5 -HT); (Serotonin) 94
Serotonin Metabolism: Melatonin 2 Steps Serotonin Melatonin: • Formed principally in pineal gland(松果腺) • Synthesis controlled by light, among other factors • Induces skin lightening • Suppresses ovarian卵巢function • Possible use in sleep disorders 95
五、Metabolism of Other Aa (自学) (一)Leu, Ile and Val (代谢途径相似) Leu Ac. Co. A + Ac. Co. A Ile Ac. Co. A + Propionyl Co. A Val Propionyl Co. A Succinyl Co. A 96
(二) Catabolism of Thr Gly + 乙醛(转化为Ac. Co. A) Thr (Liver、kidney and some microorganism) α-ketobutyrate Propionyl Co. A Butyrate + Propionate (Some microorganism) (三) Catabolism of His Glu (四) Catabolism of Lys Glu + Ac. Co. A 97
(五)Catabolism of Arg Orn Urea + Orn Glu (六)Catabolism of Ala 、Glu and Asp Affter Oxidative Deamination and Transamination, Form Pyruvate, α-ketoglutarate and OAA ? Another improtant rout of Glu is GAGA 支路: Glu脱羧的γ-aminobutyrate 是神经递质和大脑细胞能源 物质。 98
GABA Formation Glutamate decarboxylase Glutamate CO 2 Gamma-aminobutyrate γ-氨基丁酸 (GABA) GABA is an important inhibitory neurotransmitter in the brain Drugs (e. g. , benzodiazepines苯(并)二氮卓类, 苯(并)二氮卓类) that enhance the effects of GABA are useful in treating epilepsy(癫痫) 99
① Ala, Ser, Cys, Gly, Thr ② Asp and Asn Glu α-ketoglutarate Succinyl Co. A Ac. Co. A ⑤ Phe , Leu, Tyr, Lys, Trp ⑥ Tyr, Phe Ac. Co. A OAA ③ Gln, His, Pro, Arg ④ Met, Ile, Val Pyruvate Ac. Co. A Fumarate 105
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ü 谷氨酰胺合成酶(高等植物的主要途径) 总反应: NH 3 +ATP + α-酮戊二酸+2 H 供体将其 供体将 转移 - - COOH CH 2 +2 H CH 2 2 CH CH 2 2 Glu合成酶 C=O CHNH 2 COOH - - - - CONH 2 CH 2 + CHNH 2 COOH CONH 2 CH 2 +ADP +Pi+H 2 O CHNH 2 谷氨酰胺(贮存了氨) COOH 可做为NH 3的 - - - - COOH CH 2 +NH 3 +ATP CHNH 2 COOH 谷AA+ADP+H 2 O+Pi 114
1、丙氨酸族氨基酸的合成 包括:Ala、Val、Leu 共同碳架:EMP中的Pyruvate 记住!!! - - - COOH CH 2 CHNH 2 + CH 2 C=O CH 3 COOH - - - - COOH CH GPT 2 C=O + CH 2 CH 3 CHNH 2 COOH 117
2、丝氨酸族氨基酸的合成 § 包括:Ser、Gly、Cys § Gly碳架:光呼吸乙醇酸途径中的乙醛酸 - - Glu COOH CH 2 COOH + CH CH 2 NH 2 2 C=O Gly COOH - - - COOH + CH 2 CHO CH 2 CHNH 2 乙醛酸 COOH α-KG 119
COOH CHNH 2 +NH 3+CO 2 +2 H+ + 2 e. CH 2 OH - - COOH 2 CH 2 NH 2 Gly H 2 O Ser § Ser还有其它合成途径 § 碳架: EMP中的3 -磷酸甘油酸 记住哦! 120
3、天冬氨酸族氨基酸的合成 § 包括:Asp、Asn、Lys、Thr、Met、Ile § 共同碳架:TCA中的OAA!!! 记住哈!! Mg 2+ - - Asp + NH 3 + ATP - - - { 天冬酰胺 合酶 - - COOCH 2 转氨 CH 2 + CH 2 C=O +NH CH 3 COOCOOCOO- COOCOOCH 2 + CH NH 3 C=O COOCOO(植, 细菌) Asn + H 2 O + AMP + PPi (动) Asp + Gln + ATP Mg 2+ Asn + Glu + AMP + PPi 124
- - - O= - - - § 天冬氨酸族其它氨基酸的合成 OH COOH ATP ADP C-O-P=O NAD OH PH CH +H CH 2 2 + As Asp kinase CHNH p NA kin CHNH 2 2 DP a + s COOH e COOH CHO β-天冬 天冬氨酰磷酸 Asp CH 2 氨酸半醛 CHNH 2 L-高丝氨酸 COOH - - - Met Thr Ile α, ε-二氨基庚二酸 (4个C来自Asp, 2个C来自丙酮酸) CO 2 Lys 125
4、谷氨酸族氨基酸的合成 包括:Glu、Gln、Pro、Hyp、Arg 共同碳架:TCA中的α-KG!!! α-KG Glu 为还原同化作用 α-KG+ NH 3 +NADH DHase Glu +NAD+ +H 2 O Synthetase Glu +NH 3 +ATP Gln + α-KG Glu合酶 Gln+ADP+Pi+H 2 O (动物和真菌,不普遍) 2 Glu(普遍) NADPH+H+ NADP+ 127
由Glu COOH NAD(P)+ COOH ATP Mg 2+ ADP COOH C H 2 C CH 2 CHNH 2 H 2 C CH 2 HC CHCOOH CHO (谷氨酰半醛 ) H HO (△’-二氢吡咯-5 -羧酸) - - - - CH 2 CHNH 2 Pro CH 2 NADH NAD+ 1/2 O 2 CHCOOH NH (羟脯AA) N (Pro) H 2 C CH 2 H 2 C CHCOOH NH 128
§ 由Glu 其它AA N-乙酰谷氨酰半醛 COOH - - - - - 氨甲酰磷酸 转甲酰酶 磷酸 - - - - - CH 2 CHNH 2 COOH - - CH 2 天冬氨酸 CHNH 2 COOH 精氨酰琥珀酸 CH 2 CHNH 2 COOH - O= - - CH 2 延胡索酸 CHNH 2 COOH CH 2 - - - 精氨酸 裂解酶 CH 2 NH 2 - - COOH CHO + CH 2 转乙酰酶 CH 2 NADPH+H NADP+CH 2 转氨作用 CH 2 Ac. Co. A CH 2 CHNH 2 HC-NH-C-CH 3 COOH NH NH 2 COOH NH 2 C-NH 2 C=N-CH C=O NH NH CH 2 COOH CH 2 鸟氨酸 瓜氨酸 129
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