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Biochem > Amino Acid metabolism L45, 46, 50 > Flashcards

Amino Acid metabolism L45, 46, 50 Flashcards

1
Q

Essental AA

A 
Phenylalanine
Valine
Thryptophan
Threonine (T and Rs) 
Isoleucine
Methionine
Histidine
Arginine
Leucine
Lysine

PVT TIM HALL

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2
Q

What are the enzymes involved in digestion of proteins?

A

1) Pepsin (Gut)

2) Trypsin
Carboxy-peptidase
Elastase
CHymotrypsin (Pancreas)

3) Tri/dipeptidase
Amnino-peptidase (Intestine lining cells)

All secreted as zymogens

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3
Q

What are the Hormones that affect the digestion of proteins?

A

Cholecystokinin (pancreas)
secretin (intestine cells)

secreted when FA get to the lumen of the intestin

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4
Q

What does cholecystokinin do?

A

1) Acts on gut to decrease its motility (stop sending stuff to intestine we’re full)
2) Secretes Bile so that it can act on fats
3) effect on satiety and feeding behavior
4) Acts on pancreas so that it secretes the digestive enzymes

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5
Q

What does secretin do?

A

Triggers the pancreas to secrete bicarbs so that it makes the bolus of food coming from gut less acidic and that the environment of enzymes is optimal

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6
Q

what is special about secretin and cholecystokinin?

A

They are secreted as zymogens and then they are activated by being cleaved so they are about 8 aa long

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7
Q

Steps of digesting proteins

A

1) proteins (before getting in the gut)
2) Action of pepsin: Polypeptide and aa
3) Intestin: all the: Oligopeptide and aa
4) Dipeptide/tripeptide
5) aa

They all go to the liver at the end through the hepatic circulation

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8
Q

What are diseases related to malabsorption of amino acids?

A

1) Cystinuria (COAL)
2) Hatrnup disease (Trp)
3) kawrshiokor

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9
Q

What is Cystinuria?

A

AR, 1:7000
Most prevalent aa disorder
77AA transporter in intestine (towards portal circulation) and kidneys- proximal tubule (to be reabsorbed)

Cysteine (non-essential)
Ornithine
Arginine (conditional essential)
Lysine (essential)
all these AA are defective and appear in the urine

Cysteine is not reabsorbed

  • > Goes in the urine
  • > creates kidney stones
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10
Q

what is the most prevalent aa disorder?

A

Cystinuria

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11
Q

Hartnup

A 
Deficiency in Tryptophan absorption
Lack of Trp --> lack of NAD+
Same symptoms of Pellagra (lack of niacin- B3): 3D's
Dermatitis- photosensitive
Diarrhea
Dementia

Imagine man in the bathroom all the time w bad skin but that is good bc he cannot remember it. His name is Hartup Pellagra

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12
Q

What happens in Cystinuria?

A

We get a - N balance because we have a def in an essential aa so we will break down our own proteins to get it

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13
Q

When do we get + N balance

A

We make more protein than we lose aa

Pregnancy, growth

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14
Q

When do we get - N balance

A

1) Not eating enough proteins in the diet
2) Not eating enough proteins w essential aa
3) Wasting diseases like burns, trauma so we are losing aa and we degrade our own proteins to get enough

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15
Q

How are amino acids metabolized?

A

aa + alphaketoglutarate
—> alpha keto acid + glutamate

E = Aminotransferase or Transaminase

Always has Pyridoxal Phosphate attached to its active site

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16
Q

What do the amino transferases do?

A

They transfer amino group from aa to alphaKG
so AKG becomes glutamate which now carries the amino grp bc we cannot let amino come off as ammonia

alpha C of amino group becomes C=O

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17
Q

What is Pyridoxal Phosphate

A

This is a cofactor to all aminotrasnferases
Derived from B6
It can reduced to become pyridoxamine P and then it can get oxidized back to become aldehyde again

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18
Q

What is alpha keto acid of Alanine?

A

Pyruvate
E= Alanine Aminotransferase
-> Liver damage test

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19
Q

What is alpha keto acid of Aspartate?

A

OOA

E= Aspartate Aminotrasnferse
-> Liver damage test

Glutamine is a donor of amino group in order to form Aspartate

Aspartate is important bc that and Glutamate are the 2 N sources for urea cycle

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20
Q

When is it useful to check for liver damage?

A

After amannita Phalloides the mushroom w/ alpha amanitin poisoning

High ALT, and Bilirubin
-> hepatic cell lysis

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21
Q

What are the sources of amino acids present in the body?

A

1) Dietary prorteins
2) Breakdown of our own proteins in the body
3) Synthesis from non-N precursors (Ex: make Alanine from pyruvate)

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22
Q

What are the products of amino acid synthesis?

A

1) NH3 and that goes to the urea cycle
2) Alpha keto acids which can be intermediates to make glucose
3) Alpha keto acids which can be intermediates to make ketone bodies
4) Co2 and H2O

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23
Q

Describe the reaction of Glutamate Dehydrogenase.

What are its goals? Where does it happen?

A

The goals are to get rid of N on Glutamate and it happens in the liver.
It is a reversible reaction

To get rid of N from Glu
Glu + NAD+ —> alpha-KGR + NADH + NH3

When we have too much NH3 in the liver that the urea cycle cannot handle:
alpha-KGT + NADPH —> Glu + NADP+

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24
Q

How is the reaction of Glu dehydrogenase regulated?

A

It is stimulated allosterically by ADP
Inhibited Allosterically by GTP

E we want the reaction to work so we can make energy out of the alpha keto acids made

E&raquo_space; -> we do not need to break down the amino acids for energy so the reaction will be inhibited

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25
Q

What is an important amino acid in the brain to maintain the functions?

A

D- serine

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26
Q

What is D-serine? How is is made?

A

D-serine is the racemic image of L- serine

It is made from L-serine using the E: RACIMASE

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27
Q

How is D-serine Degraded?

A

It is degraded using FAD –> alpha KGT + H2O2+FADH2+ NH3

Enzyme D-AMINO ACID OXYDASE (DAO)

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28
Q

what is the function of D-amino acid in the brain?

A

1) Monitors the N-Methyl D-Aspartate- type glutamate receptor transmission
2) Synastic Plasticity
3) Development

It is a :) guy!

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29
Q

What happens if DAO activity levels go up?

A

This would lead to decrease D-serine in the brain
and an increase in H2O2

csq: 1) Increase risk of schizophrenia
2) Aging
3) Neurodegeneration

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30
Q

How can the NH3 be moved from muscle to liver?

A

NH3 is toxic so it needs carriers: Gln and Ala

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31
Q

How can Gln move NH3 from the muscle to the liver?

A

In the muscle, when +ATP and +NH3

Glu+NH3+ATP —–> Gln E: GLUTAMINE SYNTHASE

glutamine goes to the liver

1) Gln –> Glu+ NH3 E= GLUTAMINASE
NH3 goes to the urea cycke
2) Glu —> alpha-KGR +NADH + NH3 E= GLU DEHYDROGENASE
alpha-kgt can then be taken care of by the liver

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32
Q

How can Ala move NH3 from the muscle to the liver?

A

There is a Glucose-Alanine cycle between Muscle and Liver

In the muscle when we have a lot of NH3
alpha-KGT + NADPH + NH3 —> GLU + NADP+
Then we use Ala transaminase reaction but in reverse
Glu + Pyruvate (from Glu) –> Ala + Alpha KGT which can be used more to get rid of more NH3

Ala goes to the liver
Ala Aminotrasnferase is then used in the forward direction
Ala+ AKGT –> Glu + Pyruvate
Glu –> NH3 + AKGT E= GLU DEHYDROGENASE
Pyruvate will make glucose though gluconeogenesis

Glucose goes to the muscle
Glycolysis –> Pyruvate which is used w/ Glu to get rid of more NH3

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33
Q

When we want to get rid of ammonia in a cell, which enzyme should I think about?

A

Glutamate Dehydrogenase!

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34
Q

What is a cofactor used by all Amino Acid Aminotrasnferases?

A

Pyridoxal Phosphate

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35
Q

What would happen if Glu dehydrogenase is deficient?

A

We would have ammonia toxicity

If this happens in the liver, this would cause hepatic encephalopathy mainly due to the hyperammonemima

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36
Q

What are the exclusively ketogenic aa?

A

Leucine

Lysine

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37
Q

What are the ketogenic and glycogenic aa?

A

Isoleucine
Phenylalanine
Tryptohane
Tyrosine

Wen Yalli indo Food?

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38
Q

Which aa are conditionally essential?

A

Glu

Asparagine

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39
Q

What are the possible products of the metabolism of aa?

A 
Acetyl CoA
Pyruvate
alpha Ketoglutarate 
Fumarate
Succinyl CoA
Acetoacetate
OAA
40
Q

Alpha Keto acid of Asparagine?

A

OOA

41
Q

How is Asparagine metabolized?

A

Asparagine —-> Aspartate + NH4+ E=ASPARAGINASE

Aspartate + AKGR —> Glu + OAA using PLP E=ASPARTATE TRASNAMINASE

42
Q

What is important about the metabolism of Asparagine?

A

It can be used to treat leukemia
Some cancer cells lack the enzynes to make asparagine,
Tx: provide leukemic cells w/ aspariginase so that these cells lack Asparagine even more and hence cannot proliferate

43
Q

What enzyme is targeted in leukemia drug treatment?

A

Asparaginase

Asn –> Asp

44
Q

What is the alpha keto acid of Histidine?

A

AKGT

45
Q

How is histidine metabolized?

A

Histidine —> Uronic Acid + NH4+ E=HISTIDASE
Ironic Acid –> —> N-forminoGlutamate
N-forminoglutamate + BH4 —> Glutamate + BH2

46
Q

What non-essential amino acid can we make from Histidine?

A

Glutamate

47
Q

How can we get glutamate in the body?

A

1) From aminotransferase reaction
2) From diet
3) From Histidine metabolism

48
Q

How is Phe metabolized?

A

Through Tyrosine
Phe + BH4 –> Tyrosine + BH2
E= PHE HYDROXYLASE

tyrosine –> Fumarate or Acetoacetate
–> Ketogenic and Glucogenic

49
Q

What is PKU

A

He cannot be metabolized bc of lack of Phe hydroxylase

50
Q

What is important in the reaction of Phe Hydroxylase?

A

Tretrahydoxybiopterin is a cofactor.
BH4 –> BH2
If the enzyme that makes them are defective, we have a problem
Also is the enzyme that turns BH2 back to BH4 is defective, we also get a problem

51
Q

Why is the metabolism of Met interesting?

A

1) Bc we make SAM (S-adenosylmethinine) which is an important methyl donor for many E
2) Bc we make homocysteine
3) Bc we can regenerate Met (using Vit B12 and folic acid)
4) Bc we can make cysteine using Vit B6

52
Q

What is the first reaction of Met metabolism?

A 
Met + ATP ---> SAM + PPi + Pi
E= Methionine Adenosyl Transferase
This reaction generates a lot of E
We add A on met 
aslo we get a thiomethyl S-CH3 which is a methyl donor
53
Q

What happens after we make SAM in metabolism of met

A

SAM –> SAH (S-adonesylhomocystein) + Methyl goes to a methyl acceptor
–> Homocysteine

54
Q

Homocyctein

A

Cytein + 1 extra C
Can go back to Met but needs 1st- folic acid then VitB12
Can lead to cysteine but needs Vit B6

55
Q

What happens if we have a lack of Vit B6 or B12 or folate?

A

Homocysteine can accumulate and cause disease
If we give these vitamins, we should alleviate the problem
we can also limit L met in the diet so that homocysteine is not synthesized at all

56
Q

Why is a build up of homocysteine bad?

A

homocysteine as a risk factor for cardiovascular disease and homocysteinuria

57
Q

What are the branched chain amino acids?

A

Leu
Iso
Val

58
Q

What causes the maple syrup disease?

A

Metabolism of branched chains amino acid: Leu, Iso, Val

Problem in the oxidative decarboxylation step

59
Q

How is the metabolism of branched chains amino acid occur?

A

1) Transamination by the same enzyme
2) Oxidation Decarboxylation and hence we get the alpha keto acid CoA corresponding
3) FAD linked dehydrogenation

We get at the end the alpha keto acid corresponding to each aa

60
Q

AKA of leucine?

A

AcetoAcetate, Acetyl CoA

61
Q

AKA of val and isoleucine?

A

AcetylCoA

SuccinulCoA

62
Q

Which aa are the cathecolamine derived from?

A

Tyrosine

63
Q

What are cathecolamine?

A

NT
Dopamine
Norepinephrine
Epinephrine

64
Q

How can we get the Tyrosine to make cathecolamine?

A

Diet

From Phe metabolism

65
Q

Steps in making cathecolamine?

A 
1) Tyrosine+ BH4 -----> DOPA+ BH2 RDS!
E= TYROSINE HYDROXYLASE
2) DOPA + PLP ---> Dopamine through a decarboxylase
3) Dopamine ---> Norepineohine 
E= DOPAMINE BETA HYDROXYLASE
uses Cu and Vit C
4) Norepinephrine --> Epinephrine
by adding a methyl group from SAM
66
Q

What is the role of dopamine?

A

NT
controls HR, intestine, BP
lack —-> Parkinsons

67
Q

Which enzyme uses Vit C and Cu as cofactor?

A

Dopamine hydroxyls which turns Dopamine to Norepinephrine

68
Q

What is the RDS in cathecolamine biosynthesis?

A

tyroxine hydroxyls
Tyr –> DOPA
uses BH4

69
Q

What are the rate limiting cofactors in catecholamine biosynthesis?

A 
BH4,
Vit C
Cu
PLP for reaction of DOPA --> Dopamine
SAM
70
Q

How does cocaine work in the brain?

A

By inhibiting the reuptake of Dopamine and Norepinephrine

71
Q

What happens in Parkinsons?

A 
Dopamine producing neurons degeneration in subtantia niagra pars compacta in the brain
Symptoms: shortage of spontaneous movement
tremor at rest
severe constipation 
mask-like facial expression
depression
cognitive impairment 
autonomic disturbances
72
Q

What causes neurodegeneration in parkinson?

A

It is usually spontaneous

10% mutations and hereditary in for ex: parkin or alpha-synuclein

73
Q

What parts of the brain are affected in Parkinson?

A

Substantia niagra pars compacta
which also affects
nigrostrial system and striatum (motoro control –> motor problems)

74
Q

How are the cathecolamine degraded?

A

1) MAO Monoamine Oxidase -> VMA Vannilylmandeic acid

2) COMPT (dopamine) Cathechol-O-methyl transferase which transfers methyl group on OH
- -> HVAHomovanillic Acid

75
Q

What enzyme was used to target depression?

A

MAO inhibitors bc then we do not have degradation of either serotonin or epi and norepi and hence we

76
Q

What is the substrate for synthesis of serotonine?

A

Tryptophane which is an essential aa and is both ketogenic and glycogenic

77
Q

How is serotonin made?

A

trp+ BH4 —-> 5- OHtryp + BH2
E= TRYPTOPHAN HYDROXYLASE

5-OHTry + PLP –> serotonine
e=DECARBOXYLASE

78
Q

What are important cofactors in the synthesis of serotonin?

A

1) Bh4

2) PLP

79
Q

How is serotonin degraded?

A

MAO

Serotonin – OHindole acetic acid

80
Q

How can serotonin be used to treat depression

A

SSRI: Fluoxetine (Prozac)

MAO inhibitor

81
Q

Why is serotonin also important?

A

Bc it is the precursor for Melatonin (sleep inducing hormone) through an intermediate called N-acetylserotonin

82
Q

What is another name for serotonin?

A

5- OHtryptamine

5-HT

83
Q

How is melatonin made in the brain?

A

5-OHtryptamine (serotonin) –> N actylserotonin
E= AANAT (this activity changes and that is what changes the level of melatonin in the brain so that it can affect the sleep-awake cycle

N-acetylserotonin —> Melatonin
E=HIOMT whose activity remains constant

84
Q

What is the function of Glutamate in the brain?

A

It is an excitatory neurotransmitter

85
Q

What is Glu a precursor fro in the brain?

A

GABA

The major inhibitory NT

86
Q

How is GABA made from Glu?

A

Using Glu decarboxylase and PLP

87
Q

What are the nature of GABA and Glu receptors (NMDA)?

A

Ionotropic (Na+, CA2+)

Metabotropic (GPCR)

88
Q

Which NT does Morphine target?

A

GABA

89
Q

Which AA makes histamine ?

A

Histidine through His Decarboxylase and PLP

90
Q

Role of histamine

A

1) Allergic reaction

2) Secretion of acid in the stomach

91
Q

Anti-Histamine

A

1) decreases allergic reactions

2) decreases acid in the gut (antacids)

92
Q

What are the precursors for creatine P and creatine?

A

Glu and Arginine

93
Q

How is creatine made?

A

1) Arg + Gly —–> Ornithine (urea cycle) + Guanidoacetate
2) Guanidoacetate + SAM —> SAH +Creatine
E=METHYTRANSFERASE
3) Creatine + ATP –> Creatine P
E= CREATINE KINASE

94
Q

why is creatine P important?

A

1 ) High E storage molec in the muscle

2) detection of MI bcit is usually in the cells but in the case of infarction –> plasma

95
Q

What is creatinine?

A

Made from creatine nd Creatine P in the kindney

Important test for kidney function

96
Q

What reactions use BH4?

A

1) Phe Hydroxylase –> tyrosine
2) Tyrosine Hydroxylase –> DOPA
3) Tryp hydroxylase –> 5-PHtryptophan –> serotonin
4) In histidine metabolism –> glutamate

97
Q

What reactions use PLP?

A

1) All aminotrasnferase
2) Histamine from histidine w his decarboxylase
3) DOPA -> DOPAMINE
4) second reaction in makinf serotonine
5-OHtry –> serotonin
5) Glu -> GABA

Biochem (8 decks)

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