1. Amino Acid Metabolism
2018/11/10

2. 论述题
（查资料课外完成）
论述小儿偏食的害处
概述体内氨基酸的来源和主要代谢去路
论述一碳单位的代谢及生理作用
2018/11/10

3. 【目的与要求】 掌握脱氨基作用、氨的来源、去路，氨的转运…… 掌握尿素合成的部位和全过程 掌握一碳单位的概念、来源、载体和功能
需要掌握的概念：
必需氨基酸、蛋白质的互补作用、氨基酸库、脱氨基作用、SAM、PAPS……
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4. outline The nutrition of protein
The digestion、absorption and putrefaction（腐烂作用）of protein
The general metabolism of AA
Metabolism of ammonia
Individual AA metabolism
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5. Section 1 The nutrition of protein
Nitrogen balance
The requirements
Classification of amino acids
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6. Nitrogen balance Zero or total nitrogen balance:
the intake = the excretion (adult)
Amount of nitrogen intake is equal to the amount of nitrogen excreted is zero or total nitrogen balance
Positive nitrogen balance:
the intake > the excretion
during pregnancy, infancy, childhood and recovery from severe illness or surgery
Negative nitrogen balance:
the intake < the excretion
following severe trauma, surgery or infections. Prolonged periods of negative balance are dangerous and fatal if the loss of body protein reaches about one-third of the total body protein
2018/11/10

7. The requirements
The requirements of protein for the health: the minimal requirement of protein is 30~50 gram for the adult
Advice: 80 gram/day (中国营养学会) ? ? ?
2018/11/10

8. Classification of amino acids
non-essential amino acids
- can be synthesized by an organism
- usually are prepared from precursors in 1-2 steps
Essential amino acids ***
- cannot be made endogenously
- must be supplied in diet
eg. Leu, Phe…..
2018/11/10

9. 携来一两本淡色书 Nonessential Essential Alanine Arginine* Asparagine
Histidine *
Aspartate
Valine
Cysteine
Lysine
Glutamate
Isoleucine
Glutamine
Leucine
Glycine
Phenylalanine
Proline
Methionine
Serine
Threonine
Tyrosine
Tyrptophan
携来一两本淡色书
*The amino acids Arg, His are considered “conditionally essential” for reasons not directly related to lack of synthesis and  they are essential  for growth only
2018/11/10

10. nutritional value Legumes(豆类) poor in Trp, but rich in Lys;
Cereals (谷类) poor in Lys, but rich in Trp
Mutual complementation of amino acids
Protein deficiency-kwashiorkor, generalized edema and liver enlargement, abdomen bulged
Suggestion: the combined-action of protein in diet
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11. Section 2 The digestion、absorption and putrefaction of protein
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12. Digestive Tract of protein
Proteins are generally too large to be absorbed by the intestine and therefore must be hydrolyzed to the amino acids
The proteolytic enzymes responsible for hydrolysis are produced by three different organs: the stomach、pancreas and small intestine (the major organ)
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13. Stomach HCl (parietal cells ) and Pepsinogen (chief cells )
The pH of gastric juice is around 1.0. Food is retained in the stomach for 2-4 hrs
HCl kills microorganisms, denatures proteins, and provides an acid environment for the action of pepsin
Autocatalysis: pepsinogen is converted to active pepsin(Pepsin A) by HCl
Pepsin coagulates milk in presence of Ca2+ ions
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14. Pancreas and small intestine
Endopeptidase (pancreas)
Trypsin（胰蛋白酶）: carbonyl of arg and lys
Chymotrypsin(糜蛋白酶）: carbonyl of Trp, Tyr, Phe, Met, Leu
Elastase（弹性蛋白酶）: carbonyl of Ala, Gly, Ser
Exopeptidase (pancreas)
Carboxypeptidase A:除脯、精、赖氨酸之外的C端
Carboxypeptidase B: amino side of Arg, lys in C-terminal
Aminopeptidase (small intestine):
cleaves N-terminal residue of oligopeptidaes
Dipeptidase (small intestine)
2018/11/10

15. carboxypepidase endopeptidase
aminopeptidase
dipeptidase
Amino acids +
1/3
Amino acids
95%
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16. absorption
There is little absorption from the stomach apart from short- and medium- chain fatty acids and ethanol
Under normal circumstances, the dietary proteins are almost completely digested to their constituent amino acids, and these end products of protein digestion are rapidly absorbed from the intestine into the portal blood
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17. The classification of carrier protein:
Amino acids are transported through the brush border by the carrier protein and it is an active transport
The classification of carrier protein:
aciditic; basic; neutral and gly-carrier
2. -glutamyl cycle (-谷氨酰基循环)
3. The bi-and tri- peptidase carrier system in the intestinal mucosa cell
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18. The mechanism of AA’s absorption
K+-ATPase K+
Na+
Na+
Amino acids
outer
Carrier protein
Member
ATP
innner
ADP+Pi
Na+
Amino acids K+
Na+
intestine
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19. 2018/11/10

20. False neurotransmitter are similar with neurotransmitter
Putrefaction
Putrefaction: the process of decay of un-digestive and un-absorbed protein and the products by bacteria and fungi in the intestine ％
1.Amines(胺): AA
Amines
–CO2
False neurotransmitter are similar with neurotransmitter
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21. 2. Ammonia(氨)-1:
A. some amino acids are degraded by intestine bacteria
intestine bacteria
+ NH3 AA
Ammonia
diffuse blood
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22. 2. Ammonia(氨)-2:
B. urea from the blood to the intestine with resultant increased diffusion of NH3 into the intestine
urea
Enter instein
Urea enzyme
CO2 +2NH3
diffuse blood
ammonia
Urea in blood
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23. 3. The other toxic material: phenol, indole, hydrogen sulfide ……
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24. Section 3 The general metabolism of AA
Protein and amino acid cycle
Degradation of Amino Acids（Fate of amino group）
The metabolism of α-ketoacid
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25. Protein and amino acid cycle
1-2%
Body protein
Re-utilization for new protein synthesis
Protein degradation
75-80%
Amino acids
T1/2 ?
(half life)
Protein circulation
2018/11/10

26. Degradation of proteins
1. Degraded by ubiquitin(泛素) label
Ubiquitin binds lysine side chain
Degrade abnormal protein of her own降解细胞内异常蛋白
Targets for hydrolysis by proteosomes in cytosol and nucleus
ATP required
2. Degraded by the protease and the peptidase in the Lysosome(溶酶体）
non- ATP required
the hydrolysis-selective are bad
Degrade adventive protein降解外来蛋白质
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27. E2：carrier protein E3：ligase
The ubiquitin degradation pathway
ATP AMP+PPi
E2-SH E3
E1-S-
E2-S-
（ubiquitin）
E1-SH
E2-SH
E1-SH
E1：activiting enzyme
E2：carrier protein E3：ligase
ubiquitinational protein
ATP
19S regulate substrate
ATP
20S Proteasome
26S Proteasome
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28. a - COO Amino acid + H N R group H Degradation of Amino Acids
- Reactions in amino acid metabolism
COO -
Amino acid
Carboxylic group a
H N 3 + H
Amino group
R group
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29. 2018/11/10

30. FATE OF AMINO GROUP DEAMINATION A. Transamination
B. Oxidative deamination
C. purine nucleotide cycle
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31. A. Transamination Transamination by Aminotransferase (transaminase)
always involve PLP coenzyme (pyridoxal phosphate)
reaction goes via a Schiff’s base intermediate
all transaminase reactions are reversible
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32. Amino-transferases
Aminotransferases can have specificity for the alpha-keto acid or the amino acid
Aminotransferases exist for all amino acids except proline and lysine
The most common compounds involved as a donor/acceptor pair in transamination reactions are glutamate and a-ketoglutarate, which participate in reactions with many different aminotransferases
to an alpha-keto acid  alpha-amino acid
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33. 2018/11/10

34. Transamination
aminotransferases
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35. Glu+pyruvate
glutamate-pyruvate aminotransferase
GPT, ALT
-Ketoglutarate+Ala
Glu+Oxaloacetate
Glutamic oxaloacetictransaminase
GOT, AST
-Ketoglutarate+Asp
（草酰乙酸）
（α-酮戊二酸）
(丙酮酸）
*** ALT and AST are components of a "liver function test". Levels increase with damage to liver (cirrhosis, hepatitis) or muscle (trauma)
2018/11/10

36. B. Oxidative Deamination
L-glutamate dehydrogenase (in mitochondria)
Glu + NAD+ (or NADP+) + H2O  NH4+ + a-ketoglutarate + NAD(P)H +H+
Requires NAD+ or NADP + as a cofactor
Plays a central role in AA metabolism ?
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37. It is inhibited by GTP and ATP, and activated by GDP and ADP
urea cycle
It is inhibited by GTP and ATP, and activated by GDP and ADP
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38. Combined Deamination ?
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39. Transamination + Oxidative Deamination
Combined deamination ＝
Transamination + Oxidative Deamination
The major pathway ！！！
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40. C. purine nucleotide cycle
NH3 AA
Asp
-Keto
glutarate
IMP
H2O
aminotransferases
AST
C. purine nucleotide cycle
AMP
-Keto
acid
Oxaloacetate
2018/11/10
fumarate
malate

41. The metabolism of α-ketoacid
Biosynthesis of nonessential amino acids
TCA cycle member + amino acid α-keto acid + nonessential amino acid
A source of energy (10%) ( CO2+H2O )
Glucogenesis and ketogenesis
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42. The classification of amino acids based on α-ketoacid metabolism
* glucogenic amino acid (生糖氨基酸）: are converted into either pyruvate or one of the citric acid cycle intermediates (a-ketoglutarate, succinyl CoA, fumarate or malate)
* ketogenic amino acid（生酮氨基酸）: will be deaminated via Acetylc-CoA and thus can be made into a ketone body. such as: Leucine and lysine
* glucogenic and ketogenic amino acid（生糖兼生酮氨基酸）: isoleucine, phenylalanine, tryptophan and tyrosine, threonine
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43. Section 4 Metabolism of ammonia
Source of ammonia
Transport of ammonia
Synthesis of urea
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44. *** Sources amino acids degradation glutamine (glutaminase, kidney)
RCCO2H2NH RCHO+NH3
MAO
Monoamine oxidase
glutamine (glutaminase, kidney)
catabolism from bacteria in intestine
purine and pyrimidine catabolism
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45. Highlights of ammonia metabolism
Fix ammonia onto glutamate to form glutamine and use as a transport mechanism
Transport ammonia by alanine-glucose cycle and Gln regeneration
Excrete nitrogenous waste through urea cycle
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46. Transport of ammonia alaninie - glucose cycle * regenerate Gln
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47. Alanine-Glucose cycle
In the liver alanine transaminase tranfers the ammonia to α-KG and regenerates pyruvate. The pyruvate can then be diverted into gluconeogenesis. This process is refered to as the glucose-alanine cycle
Alanine transaminase has an important function in the delivery of skeletal muscle carbon and nitrogen (in the form of alanine) to the liver
In skeletal muscle, pyruvate is transaminated to alanine, thus affording an additional route of nitrogen transport from muscle to liver
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48. 2018/11/10

49. Gln regeneration
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50. **** Urea synthesis Synthesis in liver (Mitochondria and cytosol)
Excretion via kidney
To convert ammonia to urea for final excretion
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51. Krebs-henseleit cycle
The urea cycle：1932 by Hans Krebs and Kurt Henseleit as the first metabolic cycle elucidated
arginase
Ornithine cycle
Krebs-henseleit cycle
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52. Mitochondria cytosol OCT （鸟氨酸） （瓜氨酸） 1 2 5 3 4 2018/11/10
Carbamoyl phosphate synthetase (Mitochondrial)
Eukaryotes have two forms of CPS, the mitochondrial CPS I uses ammonia as the N donor for urea synthesis. The cytosolic CPS II uses glutamine as its N donor for pyrimidine biosynthesis
2ATP+HCO3–+NH3carbamoyl phosphate+2ADP+ Pi
2. Ornithine transcarbamoylase (Mitochondrial)
carbamoyl phosphate + ornithine  citrulline
Antiport: (cytosolic ornithine  mitochondria) coupled to (mitochondrial citrulline  cytosol)
3. Argininosuccinate synthetase (Cytosolic)
citrulline + aspartate + ATP  argininosuccinate + AMP + PPi
4. Argininosuccinase (Cytosolic)
argininosuccinate  fumarate + arginine
The skeleton of Asp is recovered in fumarate.
The reactions are the same for all organisms that are capable of synthesizing arginine
5. Arginase (Cytosolic)
   Only the ureotelic animals have large amounts of the arginase
  arginine + H2O  urea + ornithine 4
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53. UREA CYCLE (liver) 1. Overall Reaction:
NH3 + HCO3– + aspartate + 3 ATP + H2O  urea + fumarate + 2 ADP + 2 Pi + AMP + ppi
2. Requires 5 enzymes:
2 from mitochondria and 3 from cytosol
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54. Regulation of urea cycle
The intake of the protein in food：the intake↑↑urea synthesis
AGA(N-乙酰谷氨酸）：CPS I is an allosteric enzyme sensitive to activation by N-acetylglutamate（AGA） which is derived from glutamate and acetyl-CoA.精氨酸是AGA合成酶的激活剂，所以可 尿素合成。
All intermediate products accelerate the reaction
rate-limiting enzyme of urea cycle is argininosuccinate synthetase(精氨酸代琥珀酸合成酶)
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55. Hyper-ammonemia and the toxic of the ammonia
Hyperammononemia: ammonia intoxication - tremors, slurring of speech, and blurring of vision, coma/death
Cause by cirrhosis(硬化)of the liver or genetic deficiencies
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56. Mechanism of ammonia poisoning
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57. Section 5 AA metabolism individual
Decarboxylation- bioactive amines production
Metabolism of one carbon unit
Metabolism of sulfur-containing amino acids
Metabolism of aromatic amino acid
Metabolism of branched chain amino acids
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58. Decarboxylation
the decarboxylation of AAs produce some neurotransmitters’ precursors – bioactive amines
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59. -aminobutyric acid (GABA)
Glutamine can be decarboxylated in a similar PLP-dependent fashion, outputting -aminobutyric acid (neurotransmitter, GABA)
L-Glu decarboxylase
– CO2
GABA
L-Glu
维生素B6是谷氨酸脱羧酶的辅酶。治疗妊娠呕吐。
抑制中枢神经系统
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60. Histidine decarboxylase
L-Histidine
– CO2
Histidine decarboxylase
Histamine
强烈的血管舒张剂。增加血管的通透性，降低血压，甚至死亡。
Histamine
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61. 5-hydroxytryptophan （5-HT）
– CO2
Hydroxylase
decarboxylase
5-HT
5－羟色胺
在脑内，抑制作用；在外周组织，强烈的血管收缩作用。
2018/11/10

62. Polyaminies: (putrescine腐胺,spermidine精脒,spermine精胺)
CO2 is then cleaved off in a PLP-dependent decarboxylation, resulting in the polyaminies (such as: SAM, spermidine, spermine)
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63. 2018/11/10

64. 多胺能与DNA及RNA结合，稳定其结构，促进核酸及蛋白质的合成。 在生长旺盛的组织，如胚胎、再生肝及癌组织中，多胺含量升高。
2018/11/10

65. One carbon unit metabolism
One carbon unit: some AA may turn into the group including one carbon in the AA metabolism
Such as:
methl CH 甲基
methylene CH 亚甲基/甲烯基
methenyl CH= 次甲基/甲炔基
formyl CHO 甲酰基
formimino CH=NH 亚氨甲基
But without CO2
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66. Carrier of one carbon unit –FH4
Synthesis of FH4
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67. Forms of one carbon unit in FH4
N5，N10-CH2-FH4
N5-CH3-FH4
N5,N10=CH-FH4
N10-CHO-FH4
N5-CH=NH-FH4
2018/11/10

68. THF – biosynthetic pathways
There are three important biosynthetic precursors synthesized from THF：
N5,N10-methylene-THF
N5-methyl-THF
N10-formyl-THF
N5,N10-methylene-THF acts in a central processing role in the synthesis of all of these enzymes: in order to synthesize either of the other two, one must first produce N5,N10-methylene-THF
N5,N10甲烯四氢叶酸
2018/11/10

69. Serine Hydroxymethyl Transferase
Glycine
CO2+ NH3
Serine Hydroxymethyl Transferase
biosynthesis
methionine
Histidine
N5-methyl-THF
THF
NADH
NAD+
biosynthesis
thymidylate
N5,N10-methylene-THF
N5,N10甲烯四氢叶酸
NADPH
NADP+
NAD+
THF
N5,N10-methenyl-THF
N5,N10甲炔四氢叶酸
Glycine
cataboase
H2O
biosynthesis
purines
NADH
N10-formyl-THF
2018/11/10
Tryptophan

70. Sulfanilamide (磺胺) is a compound that the human body can create
Sulfanilamide (磺胺) is a compound that the human body can create. It is a close analog to PABA, and it has the effect of stopping folate synthesis in bacteria. There are a wide variety of “sulfa drugs ” (磺胺类药) based on PABA analogs such as sulfanilamide
Trimethoprim (TMP) and pyrimethamin(百炎净), on the other hand, are DHFR inhibitors. Because bacterial DHFR is structurally simpler than human DHFR, these two drugs have a more drastic effect on bacteria than they do on us
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71. Metabolism of sulfur-containing amino acids
(CH 2 )
S-CH 3
CH-NH
COOH
—S——S—
COOH
CHNH 2 CH
COOH
CHNH 2 CH SH
cysteine
cystine
Met
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72. Methionine Catabolism
The principal fates of methionine are incorporation into polypeptide chains(protein synthesis), and use in the production of a-ketbutyrate and cysteine via S-adenosyl methionine (SAM)
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73. S-adenosyl methionine (SAM)
is a powerful methylating agent (in the methylating gene regulation of DNA and RNA, It is constantly regenerated in a cyclical) with uses in many biochemical pathways
formed from ATP and Met
Adesine transferase
– PPi +Pi
SAM
Met +
ATP
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74. S-adenosylmethionine (SAM)
methyl group is donated to form several products
norepinephrine --> epinephrine
gamma-butyric acid --> carnitine
guanidinoacetate --> creatine
(胍乙酸)
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75. Met cycle FH4 is produced!!! O H R CH SAM PPi +Pi Met ATP N5-CH3-FH4
methyl-transferase
FH4 is produced!!! O H RH R CH 2 S
(CH )
C-NH
COOH
R-CH3
SAH
H2O A
SAHH
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同型半胱氨酸
S-腺苷同型半胱氨酸

76. Only one! FH4 and Met cycle N5,N10 -methylene- FH4 同型半胱氨酸 homocysteine
NADH
Carbon donors (serine, glycine) combine with THF
NAD+
N5-CH3-FH4
FH4
Only one!
同型半胱氨酸
homocysteine
methionine
vitamin B12
adenosine
ATP
FH4 and Met cycle
all 3 phosphate groups are lost!
This FH4 can then go and interact with serine or glycine to regenerate N5,N10 -methylene-THF-which can either be used to generate more N5-methyl-THF, or generate N10-formyl-THF
Therefore, folates are reused and conserved
H2O
PPi + Pi
s-adenosylhomocysteine
s-adenosylmethionine
S-腺苷同型半胱氨酸
methyl group donated to biological substrate, e.g. norepinephrine
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77. Regulation of the Met metabolism
If methionine and cysteine are present in adequate quantities, SAM accumulates and is a positive effector on cystathionine synthase(胱硫醚合成酶), encouraging the production of cysteine and a-ketobutyrate
If methionine is scarce, SAM will form only in small quantities, thus limiting cystathionine synthase activity. Under these conditions accumulated homocysteine is remethylated to methionine, using N5-methyl THF and other compounds as methyl donors
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78. Metabolism of Cystine and Cysteine2
cysteine
– 2H
—S——S—
cystine
+ 2H
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79. Cysteine Catabolism
The pathway is catalyzed by a liver desulfurase and produces pyruvate and hydrogen sulfide (H2S)
The enzyme sulfite oxidase uses O2 and H2O to convert HSO3- to sulfate (SO4-) , and H2O2. The resultant sulfate is used as a precursor for the formation of 3'-phosphoadenosine-5'-phosphosulfate, PAPS
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80. Taurine
L-cysteine can be decarboxylated and converted into outputted the taurine(牛磺酸)
L-Cys
Decarboxylase
-CO2
3（O）
taurine
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81. Metabolism of aromatic amino acid
Phenylalanine
Tyrosine
tryptophan
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82. Phenylalanine hydroxylase
Phenylalanine metabolism
Phenylalanine hydroxylase
THF
DHF
Phenylalanine normally has only two fates: incorporation into polypeptide chains, and production of tyrosine via the tetrahydrobiopterin(四氢生物蝶呤)-requiring phenylalanine hydroxylase
NADP+
NADPH+H+
tyrosine
phenylalanine
2018/11/10

83. Tyr metabolism 1. Catecholamine/melanin 2018/11/10
Tyrosine can be converted into l-DOPA (Dihydroxyphenylalanine) by the action of l-DOPA Decarboxylase, which requires PLP as a cofactor and outputs a CO2 and Dopamine
Dopamine can then be converted to Norepinephrine (去甲肾上腺素) , which can then be converted into Epinephrine(肾上腺素)
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84. Tyr Catabolism Homogentisate Tyr Tyr aminotransferase NH3+ |
- CH2 - CH - COO-
CH2 - COO-
HO OH
Homogentisate
尿黑酸
NH3+ |
- CH2 - CH - COO-
HO -
Tyr
Phe
Hydroxylase
对羟基丙酮酸 O ||
- CH2 - C - COO-
HO -
Tyr
aminotransferase
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85. Homogentisate cis trans acetoacetate fumarate HO - - OH 尿黑酸 CH2 - COO-
-OOC - CH = CH - C - CH2 - C - CH2 - COO-
|| ||
O O
cis
-OOC - CH = CH - C - CH2 - C - CH2 - COO-
|| ||
O O
trans
H ||
-OOC - C = C - COO H3C - C - CH2 - COO- H O
acetoacetate
fumarate
乙酰乙酸
Phenylalanine catabolism always follows the pathway of tyrosine catabolism. The main pathway for tyrosine degradation involves conversion to fumarate and acetoacetate(乙酰乙酸) , allowing phenylalanine and tyrosine to be classified as both glucogenic and ketogenic
延胡索酸
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86. IQ study: 53  93 Phenylalanine Hydroxylase & PKU
Phenylketonuria (PKU) = lack of phenylalanine hydroxylase
- can’t hydroxylate phenylalanine to tyrosine
[Phe] = 0.1 mM normally
 1.2 mM in PKU
1 in 20,000 homozygous
1 in 150 heterozygous
IQ study:
53  93
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87. People with phenylketonuria must avoid excess phenylalanine, but both tyrosine and phenylalanine are essential amino acids, so they shouldn’t exclude it completely or brain disorders with result
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88. The Metabolism of Branched Chain Amino Acids
Branched-chain amino acids (BCAAs):
isoleucine, leucine and valine
The catabolism of all three BCAAs initiates in muscle and yields NADH and FADH2 which can be utilized for ATP generation
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89. A metabolic block here causes maple syrup urine disease
Isoleucine / Leucine / Valine
-ketoglutarate
transamination
A metabolic block here causes maple syrup urine disease
glutamate
-keto acid
NAD+, CoASH
-keto acid dehydrogenase
NADH, CO2
gluconeogenesis
-keto-S-CoA
(if Leu or Lys, only
this path can be used)
Proprionyl-CoA
Succinyl-CoA
ketogenesis
2018/11/10
丙酰CoA

90. Most nitrogen metabolism pathways are very complex require many steps
require input of ATP and NADPH
are regulated by feedback inhibition mechanisms (allosteric)
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91. 选择题练习
氨基酸代谢
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92. 1. 体内氨基酸脱氨基的主要方式是( )
A 转氨基
B 联合脱氨基
C 氧化脱氨基
D 非氧化脱氨基
E 脱水脱氨基
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93. 2. 体内氨的主要代谢去路是( )
A 合成尿素
B 生成谷氨酰胺
C 合成非必需氨基酸
D 渗入肠道
E 肾泌氨排出
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94. 3. 关于胃蛋白酶,不正确的是( ) A 以酶原的方式分泌 B 由胃粘膜主细胞产生 C 可由盐酸激活 D 属于外肽酶 E 具凝乳作用
3. 关于胃蛋白酶,不正确的是( )
A 以酶原的方式分泌
B 由胃粘膜主细胞产生
C 可由盐酸激活
D 属于外肽酶
E 具凝乳作用
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95. 4. 关于一碳单位代谢描述错误的是( ) A 一碳单位不能游离存在 B 四氢叶酸是一碳单位代谢辅酶 C N5-CH3-FH4是直接的甲基供体
4. 关于一碳单位代谢描述错误的是( )
A 一碳单位不能游离存在
B 四氢叶酸是一碳单位代谢辅酶
C N5-CH3-FH4是直接的甲基供体
D 组氨酸代谢可产生亚氨甲基
E 甘氨酸代谢克产生甲烯基
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96. 5. 氨基酸脱羧的产物是( ) A 氨和二氧化碳 B 胺和二氧化碳 C -酮酸和胺 D -酮酸和氨 E 草酰乙酸和氨
5. 氨基酸脱羧的产物是( )
A 氨和二氧化碳
B 胺和二氧化碳
C -酮酸和胺
D -酮酸和氨
E 草酰乙酸和氨
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97. 6. 哪种物质缺乏会引起白化病? A 苯丙氨酸羟化酶 B 酪氨酸转氨酶 C 酪氨酸酶 D 酪氨酸脱羧酶 E 酪氨酸羟化酶
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98. 7. 血氨升高的主要原因是( ) A 体内氨基酸分解增加 B 食物蛋白质摄入过多 C 肠道氨吸收增加 D 肝功能障碍 E 肾功能障碍
7. 血氨升高的主要原因是( )
A 体内氨基酸分解增加
B 食物蛋白质摄入过多
C 肠道氨吸收增加
D 肝功能障碍
E 肾功能障碍
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99. 8. 氨基酸彻底分解的产物是( ) A 胺,二氧化碳 B 二氧化碳,水,尿素 C 尿酸 D 氨,二氧化碳 E 肌酸酐,肌酸
8. 氨基酸彻底分解的产物是( )
A 胺,二氧化碳
B 二氧化碳,水,尿素
C 尿酸
D 氨,二氧化碳
E 肌酸酐,肌酸
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100. 9. 甲基的直接提供体是( ) A S-腺苷甲硫氨酸 B 甲硫氨酸 C 同型半胱氨酸 D 胆碱 E N5-CH3-FH4
9. 甲基的直接提供体是( )
A S-腺苷甲硫氨酸
B 甲硫氨酸
C 同型半胱氨酸
D 胆碱
E N5-CH3-FH4
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101. 10. 哪种酶先天缺乏可产生尿黑酸尿症? A 酪氨酸酶 B 尿黑酸氧化酶 C 酪氨酸转氨酶 D 酪氨酸羟化酶 E 苯丙氨酸羟化酶
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102. 11. Which one is glucogenic and ketogenic amino acid? ( )
A Gly
B Ser
C Cys
D Ile
E Asp
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103. 12. The ALT most active tissue is ( )
A blood serum
B cardiac muscle
C spleen
D liver
E lung
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104. 12. The ALT most active tissue is ( )
A blood serum
B cardiac muscle
C spleen
D liver
E lung
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105. 13. The average value of nitrogen content in proteins is ( )
B 15%
C 16%
D 18%
E 24%
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106. 14. The vitamine joining in methionine cycle is ( )
A B1
B PP
C B12
D B6
E B2
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107. 15. -酮酸的代谢去路有( ) A 可转变为糖 B 可转变为脂肪 C 生成非必需氨基酸 D 氧化生成二氧化碳和水 E 生成必需氨基酸
15. -酮酸的代谢去路有( )
A 可转变为糖
B 可转变为脂肪
C 生成非必需氨基酸
D 氧化生成二氧化碳和水
E 生成必需氨基酸
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108. 16. 蛋白质消化酶中属内肽酶的有( )
A 胃蛋白酶
B 胰蛋白酶
C 氨基肽酶
D 羧基肽酶
E 弹性蛋白酶
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109. 17. 可生成或提供一碳单位的氨基酸有( )
A 丝氨酸
B 组氨酸
C 甘氨酸
D 色氨酸
E 甲硫氨酸
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110. 18. 嘌呤核苷酸循环中参与的物质有( ) A 草酰乙酸 B -酮戊二酸 C 腺嘌呤核苷酸 D 次黄嘌呤核苷酸 E 苹果酸
18. 嘌呤核苷酸循环中参与的物质有( )
A 草酰乙酸
B -酮戊二酸
C 腺嘌呤核苷酸
D 次黄嘌呤核苷酸
E 苹果酸
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111. 19. The amino acids which join in ornithine cycle are ( )
A aspartic acid
B citrulline
C N-acetylglutamic acid
D arginine
E ornithine
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112. 20. The main transporting forms of ammonia between tissues are ( )
A urea
B ammonium ion
C ammonia
D alanine
E glutamine
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113. The end
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