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MCP > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

ammonia toxicity is seen in (2)

A

liver failure

inborn errors of metabolism

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2
Q

Effects of ammonia intoxicatio in inborn errors of metabolism n are primarily

A

on the nervous system, leading to dizziness, coma, convulsions

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3
Q

ammonia toxicity in liver failure is tx with

A

dietary restriction

eat as little protein as possible, only essential aa

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4
Q

Symptoms of Ammonia Toxicity include:

A

Irritability

V omiting

Lethargy & confusion

Respiratory distress

Migraines

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5
Q

POSSIBLE MECHANISMS FOR AMMONIA TOXICITY

Brain glutamate dehydrogenase forms glutamate from _____

A

α-ketoglutarate and NH3

this lower pools of α-ketoglutarate

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6
Q

effect of lowered pool of α-ketoglutarate after it is converted with nh3 to glutamate

A

flux through tca cycle is reduced

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7
Q

POSSIBLE MECHANISMS FOR AMMONIA TOXICITY

Increased glutamate leads to increased ______ from the excess NH

A

inc glutamine

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8
Q

POSSIBLE MECHANISMS FOR AMMONIA TOXICITY

. Increased glutamate leads to increased glutamine from the excess NH3 —-> effect

A

brain pools of glutamate decrease (affecting NT glutamate levels and gaba)

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9
Q

POSSIBLE MECHANISMS FOR AMMONIA TOXICITY

Glutamine leaves brain neurons in exchange for ____

A

tryptophan.

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10
Q

POSSIBLE MECHANISMS FOR AMMONIA TOXICITY

Glutamine leaves brain neurons in exchange for tryptophan —->

A

Trp is converted to serotonin —> high serotonin thought to be cause of coma in liver failure

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11
Q

____ is thought to be an important factor in coma associated with liver failure.

A

High serotonin

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12
Q

possible cause of ammonia toxicity in the brain

A

Uncontrolled changes in the levels of 3 neurotransmitters (glutamate, GABA and serotonin) in the brain.

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13
Q

The degradation of the AA carbon skeletons involves the removal of ___ and disposal of ___

A
  1. removal of nitrogen
  2. disposal of carbon skeletons
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14
Q

Ketogenic- amino acids are degraded to either

A

acetyl coenzyme A or acetoacetyl CoA

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15
Q

_ Ketogenic_- amino acids are degraded to either acetyl coenzyme A or acetoacetyl CoA, which give rise to ____

A

ketone bodies

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16
Q

Glucogenic- amino acids are degraded to ___

A

pyruvate or citric acid cycle intermediates,

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17
Q

Glucogenic- amino acids are degraded to pyruvate or citric acid cycle intermediates, which can give rise to ____ via formation of ____

A

glucose via formation of phosphoenolpyruvate.

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18
Q

_____ amino acids can provide an excellent source of glucose after glycogen stores are gone.

A

Glucogenic

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19
Q

can the ** carbons in ketones and acetyl-CoA** can or cannot be converted into glucose,

A

cannot be converted into glucose

can only be converted into FA

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20
Q
  • Some amino acids can be degraded into multiple intermediates which can be classified as
A

ketogenic and glucogenic.
[I, F, Y, W, T]

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21
Q

amino acids that are exlcusively ketogenic

A

leucine
lysine

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22
Q

five amino acids are both ketogenic and glucogenic:

A

isoleucine
phenylalanine
tryptophan
tyrosine
threonine

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23
Q

amino acid degradation

Alanine is converted to pyruvate by transamination with α-ketoglutarate by

A

alanine transaminase

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24
Q

Serine is converted to pyruvate by ____ by serine dehydratase.

A

direct deaminatio

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25
Q

Cysteine can be converted to pyruvate by a ___

A

desulfhydrase.

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26
Q

Glycine is converted by____ to serine

A

serine hydroxymethyltransferase

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27
Q

Glycine is converted by serine hydroxymethyltransferase to _____

A

serine

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28
Q

Glycine is converted by serine hydroxymethyltransferase to serine, which is then converted to ____

A

pyrvuate

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29
Q

how to get from glycine to pyrvuate?

A

glyceine —> serine —> pyruvate

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30
Q

Glycine is converted by serine hydroxymethyltransferase to serine

was is taken up? what is removed?

A
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31
Q

how can glyceine be broken down into Co2 and free ammonia?

A

Glycine Cleavage Enzyme (glycine synthase, run in reverse)

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32
Q

glycine—> co2 and NH4

what is given off

A
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33
Q

glycine—>

via GLYCINE CLEAVAGE ENZYME

A

CO2 + NH4

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34
Q

how to get pyvuravate from threonine?

A

threonine –> glycine —> serine —> pyvruvate

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35
Q

threonine –> glycine

via what enzyme?

A

aminoacetone

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36
Q

what is generated with aminoacetone –> glycine?

A

acetyl coa

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37
Q

Aspartate is converted by transamination with α-ketoglutarate to ______

A

oxaloacetate

38
Q

why does asparate need to be in the liver?

A

to feed ammonia groups into the urea cycle

39
Q

what is asparate converted to? what is it a marker of?

A

Aspartate is converted by transamination with α-ketoglutarate to oxaloacetate

marker of liver failure

40
Q

HOW TO GET FROM ASPARIAGINE TO OXALOACETATE?

A

ASPARAGINE —> ASPARATE —> OXALOACETATE

41
Q

ASPARAGINE –> ASPARTATE BY?

A

ASPARAGINASE

42
Q

Glutamine- converted to glutamate by ___.

A

glutaminase

43
Q

Histidine- converted to ____ by a series of reaction that include transfer of its formino group to tetrahydrofolate.

A

glutamate

44
Q

HOW IS HISTIDINE CONVERTED TO GLUTAMATE?

A

HISITIDINE –> UROCANIC ACID –> 4-IMIDAZOLONE-5-ACID —> N-FORMINOGLUTAMATE (TRANSFER OF FORMINO GROUP TO TETRAHYDROFOLATE) –> GLUTAMATE

45
Q

HOW IS ARIGINE CONVERTED TO GLUTAMATE?

A

ARIGINE –> ORNITHINE –> GLUTAMATE SEMIALDHEYDE –> GLUTAMATE

46
Q

HOW IS PROLINE CONVERTED TO GLUTAMATE?

A

PROLINE –> GLUTAMATE SEMIALDEHYDE –> GLUTAMATE

47
Q

When we synthesize arginine, we make ornithine and then

A

run it through the urea cycle.

48
Q

You can synthesize arginine, but during growth or positive nitrogen balance you need extra, since

A

in the liver it constantly be degraded to ornithine and urea.

49
Q

Valine, leucine, and isoleucine each are converted to their corresponding α-keto acid by
the actions of

A

transaminases.

50
Q

____ (3) each are converted to their corresponding α-keto acid by
the actions of transaminases.

A

Valine, leucine, and isoleucine (branched AA)

51
Q

BCAT (branched chain AA transaminase) deficiency in mice has been shown to cause

A

increased insulin sensitivity, increased protein turnover, increased serum leucine levels, decreased fat and body weight, and increased energy expenditure.

can’t converted valine, leuicen, isoleucine to corresponding a-ketoacid

52
Q

what catalyzes the oxidative decarboxylation of valine, leuiceine, isoleucine

A

a common branched-chain keto acid dehydrogenase

53
Q

what does branched-chain keto acid dehydrogenase use as cofactors?

A

lipoamide, thiamine pyrophospate, FAD and NAD.

54
Q

another name for branched chain ketoaciduria?

A

maple syrup urine disease

55
Q

what causes maple syrup urine disease

A

defect in
branched-chain keto acid dehydrogenase.

56
Q

MAPLE SYRUP URINE DISEASE –>

characteristic odor is caused by

A

build up of keto acids due to the defect in branch chaoin keto acid dehydrogenase

57
Q

tx of maple syrup urine disease

A

restricted diet, avoiding isoleucine, leucine, valine

some pts respond to thiamine

58
Q

Methionine, isoleucine and valine are degraded by different pathways to form___
via methylmalonyl CoA.

A

succinyl CoA

59
Q

Methionine, isoleucine and valine are degraded by different pathways to form succinyl CoA
via ___

A

methylmalonyl CoA.

60
Q

___ (3) are degraded by different pathways to form succinyl CoA
via methylmalonyl CoA.

A

Methionine, isoleucine and valine

61
Q

____ is formed by the hydroxylation of phenylalanine

A

Tyrosine

62
Q

Tyrosine is formed by the hydroxylation of phenylalanine

enymze?

cofactor?

A

Enzyme: Phenylalanine hydroxylase
Cofactor Tetrahydrobiopteri

63
Q

how can low NADH affect tyrosine levels

A

Tetrahydrobiopterin wouldnt be replenished, which is a cofactor in the pheynlaline –> tyrosine reaction

Tetrahydrobiopterin is regenerated by dihydrobiopterin reductase which uses nadh as a reductant

64
Q

Phenylketonuria is a genetic disorder associated with the inability to catalyze the

A

hydroxylation of phenylalanine the subsequent accumulation of toxic derivatives of phenylalanine such as phenylpyruvate.

65
Q

PKU TX

A

phenylalanine restricted diet until the age of at least 16y/o.

66
Q

GENE MUTATIONS CAUSING A REDUCTION IN THE ENZYME ____ CAN CAUSE PKU

A

Phenylalanine hydroxylase

67
Q

Atypical PKU- caused by a defect in the

A

dihydrobiopterin reductase

68
Q

DIFFERENCE IN TX OF ATYPICAL PKU VS. PKU

A

NO TX FOR PKU

69
Q

WHAT IS MATERNAL PKU?

A

HIGH PHENYLALINE LEVELS IN MOTHER WITH PKU —> MENTAL RETARDATION IN FETUS

70
Q

MECHANISM OF CONVERSION OF PHENYLALINE TO TYROSINE?

A

BH4 IS A COFACTOR

NADH IS NEEDED BY BH2 REDUCTASE TO REVERT IT BACK

O2 IN, H20 OUT

71
Q

Homogentisate is converted to ___

A

4-maleylacetate

72
Q

Homogentisate is converted to 4-maleylacetate
Enzyme: Homogentisate oxidase
Defect: ____

A

Alkaptonuria

73
Q

Alkaptonuria IS CAUSED BY

A

DEFECTIVE HOMOGENTISIC ACID 1,2-DIOXYGENASE

NEEDED FOR HOMOGENTISTIC ACID–>4-Maleyl-acteoacetic acid

74
Q

Homogentisate —> 4-maleylacetate
Enzyme: ____
Defect: Alkaptonuria

A

Homogentisate oxidase

75
Q

tryptophan is an important precursor of the neurotransmitter serotonin and can contribute to the pool of

A

NIACIN

76
Q

DEFICIENCY IN WHAT AA COULD CAUSE PELLAGRA (NIACIN DEF.)

A

TRPYTOPHAN

77
Q

The degradation of lysine is complex, but eventually leads to the production of ____

A

acetyl CoA,

78
Q

___ amino acids are essential and must be acquired from the diet.

A

9

79
Q

HOW IS ALANINE FORMED?

A

A TRANSMINATION RXN FROM PYRUVATE

80
Q

HOW IS ASPARATE FORMED?

A

from oxaloacetate by a transamination reaction.

81
Q

three common methods for adding NH3 groups to molecules:

A

1) transamination
2) Asp–>Fumarate 3) Gln –>Glu.

82
Q

GLUTAMATE FORMATION? (2)

A
  1. reductive amination of a α-ketoglutarate by glutamate dehydrogenase.
  2. transamination of α-ketoglutarate by almost any other amino acid.
83
Q

HOW IS GLUTAMIEN FORMED?

A

formed by the amidation of glutamate.

84
Q

Proline may be formed in two steps from ___

A

glutamate.

85
Q

Serine is synthesized in three steps from

A

3-phosphoglycerate, an intermediate in
glycolysis.

86
Q

Glycine can be made from ___

A

serine

87
Q

Glycine can be made from serine in a reversible reaction by

A

serine hydroxymethyltransferase

88
Q

Cysteine may be synthesized from

A

serine and methionine.

89
Q

cysteine is only nonessential if ___ is provided in the diet.

A

methionine

90
Q

Tyrosine is an essential amino acid in

A

people who dont get phenylaline in their diet

people with pku

91
Q
A

MCP (16 decks)

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