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MCG > SYLLABUS 21: Amino Acid Anabolism > Flashcards

SYLLABUS 21: Amino Acid Anabolism Flashcards

1
Q

where does non-essential aa synthesis occur?

A

in the cytosol of all tissues

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2
Q

anabolic synthesis of glutamate?

A

Glutamate Dehydrogenase Reaction:

aKG + NH3 + NADH <-> Glutamate + NAD+

used in urea cycle

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3
Q

anabolic synthesis of glutamine?

A

Glutamine Synthase Rxn:

Glutamate + ATP + NH3 -> Glutamine + ADP + Pi

*used in urea cycle to transfer ammonia from muscle & other tissue to liver *

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4
Q

anabolic synthesis of aspartate?

A

GOT transamination reaction:

Glutamate + OAA <-> aKG + Aspartate

these are TCA cycle intermediates

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5
Q

asparagine anabolic synthesis?

A

Asparagine synthase rxn:

Aspartate + Glutamine + ATP -> Asparagine + Glutamate + ADP + Pi

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6
Q

Alanine anabolic synthesis rxn?

A

GPT or Ala aminotransferase rxn:

Pyruvate + glutamate <-> Alanine + a-KG

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7
Q

what is the alanine:glucose cycle?

A

when exercising muscle uses lots of glucose & therefore produces lots of pyruvate, exceeds the capacity of the PDH and LDH reactions

excess pyruvate -> alanine by the Muscle GPT reaction

alanine leaves mucle, circulates to liver, where -> pyruvate by Liver GPT

Pyruvate -> gluconeogenesis

Glucose is secreted from liver, -> muscle to be used for energy via glycolysis

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8
Q

what non-essential aa is found in high levels in the blood during exercise?

A

alanine, traveling to liver to undergo liver GPT reaction to become pyruvate and undergo gluconeogenesis there in liver

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9
Q

proline anabolic synthesis rxn?

A

glutamate -> gamma-glutamic semi-aldehyde -> proline

*gamma glutamic semi-aldehyde can -> ornithine, thus it is a precursor to either proline or ornithine *

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10
Q

arginine anabolic synthesis rxn?

A

glutamate -> ornithine, which reacts w/ Carbamyl P + Aspartate -> Urea Cycle -> Arginine

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11
Q

is arginine an essential aa?

A

in adults, no - they get enough from glutamate, carbamyl P, and aspartate

in children or growth/development, yes - do not get enough arginine in this pathway to sustain maximal development

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12
Q

rxn for anabolic synthesis of cysteine?

A

Methionine + Serine via Cystathionine

  • in Transsulfuration pathway *
  • Methionine provides the S, Serine provides all over atoms*
  • Methione is from homocysteine*
  • Serine is from cystathione *
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13
Q

is cysteine essential or non essential?

A

NON-ESSENTIAL as long as methionine is in excess

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14
Q

how is tyrosine anabolically synthesized?

A

phenylalanine hydroxylase rxn:

Phenylalanine - O2, thb, Phe, OH -> tyrosine + dhb + H2O

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15
Q

is tyrsoine nonessential or essential?

A

nonessential as long as there’s sufficient phenylalanine in diet

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16
Q

anabolic synthesis rxn for serine?

A

1. From glycolysis intermediate:

3PG -> -> Serine

Serine transhydroxymethylase reaction:

Glycine + N5N10CH2THF <-> Serine + THF

17
Q

is serine an essential or nonessential aa?

A

non-essential as long as either:

  1. glucose is being metabolized to 3PG or glycine and
  2. a C atom from folate pool is available
18
Q

glycine anabolic synthesis rxn?

A

1. From serine:

Serine + THF <-> Glycine + N5N10CH2THF

2. **De novo:

CO2 + NH3 + N5N10CH2THF + NADH -> Glycine + THF + NAD+

19
Q

what is the #1 donor of C atoms into the folate pool?

A

Serine

20
Q

where does glycine reaction’s methylene come from?

A

histidine or another serine

21
Q

why can benzoat be used as a treamtn for ammonia intoxication?

A

when add benzoic acid to reaction, it reacts w/ glycine; ammonia gets incorporated into glycine, which then conjugates w/ benzoate

this forms the soluble hippuric acid

hippuric acid is excreted, and so is ammonia

22
Q

what are catecholamines?

where are they synthesized?

function?

A

_DOPA, Dopamine, Norepinephrine, Epinephrine _

synthesized in: brain and adrenals

function: neurotransmitters, regulators of blood flow, blood pressure, metabolism, energy production

23
Q

pathway of catecholamine synthesis?

A
  1. tyrosine hydroxylase rxn converts tyrosine -> DOPA; uses THB, O2 as cofactors

rate limiting enzyme

  1. DOPA -> Dopamine + CO2 by Dopa decarboxylase, sues PLP as cofactor
  2. Dopamine -> Norepinephrine by Dopamine B-hydroxylase, uses Vitamin C (Ascorbate)
  3. Norepinephrine -> Epinephrine by Phenylethanolamine N-methyl transferase, uses SAM
24
Q

function of DOPA?

A

mostly to synthesize dopamine, norepinephrine, epinephrine

25
Q

Dopamine function?

A

critical neurotransmitter, helps control coordination, motor control, mood

26
Q

what does dopamine deficiency cause?

A

deficiency in **substantia nigra **of brain -> Parkinson’s disease

27
Q

MAO?

A

monoamine oxidase

oxidizes monoamines - neurotransmitters like Dopamine, Norepinephrine, Epinephrine - removes them, produces H2O2 in producess

so brains are subject to H2O2 production all the time

espeically occurs in **substantia nigra **of brain - and H2O2 presence prevents production of Dopamine in this region of brain

28
Q

treatment for Parkinson’s?

A

provide DOPA, which can cross blood-brain barrier, rather than Dopamine, which is positively charged at physiologic pH and cannot cross blood-brain barrier

in the substantia nigra, Dopa -> Dopamine

eventually, treatment stops working b/c resistance to Dopa develops

29
Q

function of norepinephrine?

A

vasodilator

critical for maintaining blood flow, blood pressure

30
Q

which 2 non essential aa become essential if their precursor aa isn’t present

A

Cysteine and Tyrosine

31
Q

which 2 non essential AA can be formed in 1 step by direct trasnamination

A

alanine, aspartate

32
Q

what key role does foalte play in interconversion between serine and glycine

A

provides the exstra C atom needed for serine<->glycine

methyl donor

33
Q

what are catecholamines? what are their functions?

A

chemicals – DOPA, Dopamine, Norepinephrine, Epinephrine –produced from Tyrsosine, synthesized in the brain and adrenals, that function as neurotransmitters and controllers of blood flow, blood pressure, metabolism, and energy production

34
Q

what is major problem in individuals w/ parkinson’s disease?

what catecholamine is used for treatment?

A

Individuals with Parkinson’s have a deficiency in the catecholamine Dopamine in the substantia nigra of the brain because of the action of Monoamine Oxidase, which oxidizes Dopamine and produces H2O2 which, in abdunace in the substantia nigra, prevents Dopamine synthesis.

DOPA is used for treatment because it can cross the blood-brain barrier and become DOPAMINE, whereas DOPAMINE itself cannot cross the blood-brain barrier

35
Q

what cofactor is used in each of the 3 stepf of tyrosine -> norepinephrine conversion?

A
  1. Tyrosine hydroxylase- THB + O2
  2. DOPA Decarboxylase- PLP
  3. Dopamine B-hydroxylase- Vitamin C (ascorbate)

MCG (77 decks)

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