SYLLABUS 21: Amino Acid Anabolism Flashcards Preview

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Flashcards in SYLLABUS 21: Amino Acid Anabolism Deck (35):

where does non-essential aa synthesis occur?

in the cytosol of all tissues


anabolic synthesis of glutamate?

Glutamate Dehydrogenase Reaction: 

aKG + NH3 + NADH Glutamate + NAD+


used in urea cycle


anabolic synthesis of glutamine?

Glutamine Synthase Rxn: 

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


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


anabolic synthesis of aspartate?

GOT transamination reaction: 

Glutamate + OAA aKG + Aspartate


these are TCA cycle intermediates


asparagine anabolic synthesis?

Asparagine synthase rxn: 

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



Alanine anabolic synthesis rxn?

GPT or Ala aminotransferase rxn: 

Pyruvate + glutamate Alanine + a-KG 


what is the alanine:glucose cycle?

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 



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

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


proline anabolic synthesis rxn?

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

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


arginine anabolic synthesis rxn?

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



is arginine an essential aa?

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


rxn for anabolic synthesis of cysteine?

Methionine + Serine via Cystathionine

in Transsulfuration pathway  

Methionine provides the S, Serine provides all over atoms

Methione is from homocysteine

Serine is from cystathione 


is cysteine essential or non essential?

NON-ESSENTIAL as long as methionine is in excess 



how is tyrosine anabolically synthesized?

phenylalanine hydroxylase rxn: 

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



is tyrsoine nonessential or essential?

nonessential as long as there's sufficient phenylalanine in diet


anabolic synthesis rxn for serine?

1. From glycolysis intermediate:

3PG -> -> Serine 

Serine transhydroxymethylase reaction:

Glycine + N5N10CH2THF Serine + THF 


is serine an essential or nonessential aa? 

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 



glycine anabolic synthesis rxn?

1. From serine:

Serine + THF Glycine + N5N10CH2THF 


2. De novo:

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



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



where does glycine reaction's methylene come from?

histidine or another serine


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

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


what are catecholamines?

where are they synthesized? 


DOPA, Dopamine, Norepinephrine, Epinephrine 

synthesized in: brain and adrenals 

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


pathway of catecholamine synthesis? 

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

rate limiting enzyme 

2. DOPA -> Dopamine + CO2 by Dopa decarboxylase, sues PLP as cofactor

3. Dopamine -> Norepinephrine by Dopamine B-hydroxylase, uses Vitamin C (Ascorbate)

4. Norepinephrine -> Epinephrine by Phenylethanolamine N-methyl transferase, uses SAM 


function of DOPA?

mostly to synthesize dopamine, norepinephrine, epinephrine


Dopamine function?

critical neurotransmitter, helps control coordination, motor control, mood 


what does dopamine deficiency cause?

deficiency in substantia nigra of brain -> Parkinson's disease 




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


treatment for Parkinson's?

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


function of norepinephrine?


critical for maintaining blood flow, blood pressure


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

Cysteine and Tyrosine 


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

alanine, aspartate


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

provides the exstra C atom needed for serineglycine 

methyl donor 


what are catecholamines? what are their functions?

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


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

what catecholamine is used for treatment? 

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


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

1. Tyrosine hydroxylase- THB + O2

2. DOPA Decarboxylase- PLP

3. Dopamine B-hydroxylase- Vitamin C (ascorbate)

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