s2m1 biochem – amino acid metabolism

Flashcard maker : Cindy Krause

what’s the purpose of a transaminase in break down of amino acids?

what other compound is needed?

what Vitamin is needed?

what is formed as a product?

it’s used to transfer the amino group

also needs a-ketogluterate to take the amino group

needs VitB6 (involved in the ping-pong mech)

a ketoacid of the aa & a glutamate is formed as a product



oxidation method of breaking down the glutamate formed from the transaminase rxn.

what enzyme is used?

where is this enzyme?

what does it mean to see this enzyme in the blood?

what are the byproducts?

is this rxn reversible?


glutamate dehydrogenase is used to oxidise the aa.

done in the mitochondria

severe liver damage -> will see this enzyme in the blood

NADPH & NH4 are byproducts

can reverse this rxn to form aa’s (need alot of NADH+)

how do we get rid of D-aa’s?

what’s the significance of the enzyme used?

what products can we make from it?

where does this happen?


using a d-amino acid oxidase

makes the molecule achiral

then with a transaminase can make an L-aa

oxygen is used and hydrogen peroxide is produced

thus this rxn occurs in the peroxisome to deal with it

what produces D-serine in the brain?

in response to what?

what is the D-ser used for?

what’s it’s pharmaceutical use?


in response to high glutamate concentration

D-ser is used in long-term potentiation for neurons as a co-agonist for NMDA receptors

pharm use: schizophrenia


what does the body do with the amonia produced in aa metabolism?

what’s the first step in the urea cycle?

where does this cycle take place?

amonia enters the lysosome in which the acidic environment makes amonium which isn’t watersoluble

it’s t/p to the liver where urea is made

the first step is using the enzyme carbamoylphosphate synthetase 1 to make carbamoylphosphate (requires ATP)

happens in the liver mitochondria

what is done with carbamoylphosphate in the urea cycle?

what disease is associated with this enzyme?

the enzyme ornithine transcarbamoylase transfers it to Ornithine to make Citruline

this enzyme can be defective, it’s a x-linked recessive disease and is seen also in women in x-inactivation problems

what is done with Citruline in the urea cycle?

what enzyme?

what additional amino acid is used?

what’s the product?

where does this conversion happen?

what’s the disease associated with this enzyme?

Argininosuccinate synthase uses Aspartate to make Argininosuccinate

this happens in the liver cytosol

Citrullinemia – desease if the enzyme is defective

what happens to arginiosuccinate in the urea cycle?

what’s the enzyme used?

what’s the byproduct?

what’s the product?

where does this happen?

what disease is associated with this enzyme?

what’s the treatment for it?

Arginiosuccinate lyase is used to convert it to Arginie

Fumerate is a byproduct

this happens in the liver cytosol

Arginiosuccinate aciduria is a disease of a defective enzyme

it’s treated by giving Arginine & Ornitine


what happens to arginine in the urea cycle?

what enzyme is used?

what’s the product ; byproduct?

where does this happen?

if this enzyme is defective, what are the symptoms of the disease?


Arginase makes Ornithine again (reused in the cycle), and also Urea is made

happens in the liver cytosol

defect: mental retardation

;spastic quadriplegia;



give a summary of the urea cycle

what are the symptoms of inherited;diseases that affect the enzymes in this cycle?

NH4 + stuff + Aspartate = stuff + Fumerate + Urea

disease symptoms:


Reye-syndrome (encephalopathy – fatal)

aversion against protein rich foods

feeding problems ; vomiting

ataxia, lethargy, coma, death



problems in urea cycle as a result of liver failure / cirrhosis

2 causes?

4 symptoms?



caused by alcoholism or viral hepatits



slurred speach

tremor (asterixis)

mental derangements


no alcohol, less protein in diet

replace aa with their a-ketoacids

or 2 pharmacuticals that can react w aa’s to then be excreted in urine

1. benzoate + Gly -> hippurate

2. phenylacetate + Gln -> phenylacetyl-Gln




regulation of urea cycle

breakdown of aa’s give alot of Glutamate

Glu -; converted to N-acetyl glutamate

this allosterically activates carbamoyl phosphate synthetase 1

essential aa’s

3 basic, 2 lions, what does meth do? the vallet tipped who?

3 basic: Arginine, Histadine, Lysine

2 lions: Leucine, Isoleucine

Meth puts you on a Tryp: methionine, tryptophan

Phenylalanine, Valine, Threonine

the VALlet tipped THREe PHingers-to-ALAN: Valine, Threonine, Phenylalanine

what are the two uses of the carbon chains in amino acids?

problem with excess ketones?

glucogenic – make glucose

ketogenic – make ketone bodies

excess – ketoacidosis -> diuresis


what’s the atkins diet?

how does the brain get energy?

what’s the problem with making ketone bodies?

result of diuresis?

what are the confounding factors?

low carb/high protein+fat 

glucose needed for brain thus body breaks down fat & protein (loss of lean body mass)

to much ketonebodies -> ketoacidosis

leads to diuresis: loss of water & minerals (short term weight loss)

confounding = environmental & congenital

people w/ these issues on atkins diets can succumb to shock, coma, death


how is alanine metabolised?

what enzyme is used?

what’s the product? what can this be used for?

what’s the clinical use of this enzyme?


glutamate-pyruvate transaminase (GPT) or alanine aminotransferase (ALT) transaminases alanine to make pyruvate

it’s used in gluconeogenesis

clinical: hepatocyte damage -; release enzyme into blood

what are the two pathways to break down serine?

1. gluconeogenesis path – uses alot of energy


2. serine dehydratase -; breaks down serine directly to pyruvate (used in gluconeogenesis)

what’s the breakdown pathway of aspartate & asparagine?

what is the product used for?

asparagine can be converted to aspartate by asparaginase

or the other way around by asparagine synthetase

aspartate is used to make oxaloacetate for the citric acid cycle by Aspartate Glutamate Transaminase 

this enzyme, also called AST (aspartate transaminase) is in heart/skeletal muscle/liver -> problem -> see AST in blood

how is glutamine & glutamate metabolised?

glutamine is converted to glutamate via glutaminase

glutamate is converted to oxogluterate which is used in the citric-acid cycle

the enzyme used is oxogluterate amino transferase

how is glycine metabolised?

4 ways with two diseases?

1. Bacteria converts it to Trimethylamine

2. in the peroxisome it’s converted to oxalate

– can become kidney stones if Calcium is bound

3. glycine cleavage enzyme can make amonium ; CO2

-a problem in this enzyme -; hyperglycinemia = fatal or severe mental deficiency

4. Ser-hydroxymethyl transferase can make serine out of it

how is threonine metabolized?


1. made into glycine

2. made into pyruvate

3. made into Succinyl-CoA

in folate metabolism, what is sulfanilimide used for?


it looks like the para-amino-benzoic acid in folic acid.;

normally folate is used in DNA nucleotide synthesis

sulfanilimide disrupts this process, thus slows down bacterial cell division

this gives our immune system time to kill the bacteria

what is trimethoprim used for, regarding the folate metabolism pathway?

the first step of the pathway is for folate to be converted by the enzyme Dihydrofolate Reductase

Trimethoprim inhibits this enzyme to kill bacterial cell division

what is methotrexate used for, regarding the folate metabolism pathway?
anti cancer – it inhibits the dihydrofolate reductase enzyme, thus prevents cell division

methionine metabolism;

what are the 1st two steps? byproducts?

what is the fate of Homocystine?

what disease can cause a buildup of homocystine?

met -; SAM (use 2 ATP’s & add adenosyl) -> SAH (by cleaving a methyl group) -> remove adenosyl to make Homocystine

Homocystine can be converted back into Methionine by using VitB12

A Folate dificiency will block this step thus get a buildup -> vascular disease



breakdown pathway of homocystine (from Methionine metabolism)

converted to what?

what are the reactants needed for this?

malfunction of this causes what?



final breakdown products of Met?

Serine + VitB6 + Cystathione synthase is used to convert it to Castathione

Malfunction = Homocystineuria

accumulation of homocystine -> mental retardation, lens dislocation, bone elongation, osteoperosis

RX – Met restriction 

mega dose of B6

Final products = Propionyl-CoA & Pyruvate, both used in gluconeogenesis

what is methylmalonyl-CoA synthase used for?

if it’s blocked? what’s used instead?

what is not a cure for this problem?

it uses malonic acid in FA synthesis 

if it’s blocked it uses methylmalonic acid instead

folate is not a treatment

Oasthouse disease

what’s defective?

what happens to the Methionine?

what symptoms?

intestinal Met-transporter deficient

so bacteria converts the Met to α-hydroxybutyrate which is excreted by the kidney

urine smells like oushouse (hobs in beer)

white hair, diarrhea, convulsions, mental retardation, tachypnia

methylmalonic aciduria

which pathway is blocked?

Propionyl-CoA conversion to Succinyl-CoA

Maple Syrup Urine disease

what pathway is blocked?

branch chain a-ketoacid dehydrogenase is blocked

thus the conversion from Isoleucine to Tiglyl-CoA is blocked

disease is auto recessive

mental deficiency

optic atrophy



elevated branch chain aa’s in serum

what are the branch chain amino acids?

what’s the first step of their metabolism?

where does this happen?

where does the rest happen?

Val, Ile, Leu


happens in muscle, the rest in liver

what’s the first step of Phe (phenyl alanine) metabolism?

what’s the disease associated with it?




Phe gets hydroxylated by Phenylalanine Hydroxylase to make Tyrosine

Phenylketouria results when this enzyme is defective

Mental retardation, seizures, spasticity

Rx with Phe restricted diet

Tyrosinaenemia type II

what enzyme deficient?

tyrosine aminotransferase

affects brain, eyes, skin

tyrosine can’t be converted to hydroxyphenyl pyruvate

tyrosineanemia type III

which enzyme is deficient?


p-hydroxyphenyl pyruvate oxidase

mild mental retard ; ataxia

tyrosineanemia type I

what enzyme is deficient?


Fumarylacetoacetate hydrolase

cabbage-like smell from FA’s

liver & kidney failure

liver cancer



what’s excreted?

mode of inheritance?



hawkinsin is excreted

autosomal dominant

restrict tyrosine in diet


what enzyme is deficient

get a buildup of what?


Saccharopine is deficient

it’s what converts Lysine to Saccharopine

get buildup of lysine

physical & mental retard

what causes histadineanemia?

what does it convert?


what’s the final product of histadine break down?


histidinase doesn’t function

it converts histadine into urocanate

Dx: lack of urocanate in sweat

final product of histidine breakdown is glutamate

in what tissues are these aa’s metabolised?

Glu + Gln

Val, Ile, Leu

other AA’s

Glu + Gln catabolized in the intestinal mucosa

Val, Ile, Leu transaminated in muscle, ketoacid then

catabolized to liver

other AA catabolized in the liver

what’s the overall fate of Alanine?

transaminated in the liver

pyruvate used in gluconeogensis

ammonia is t/p fr muscle to liver

what happens to Glycine in the kidney?

what about in the intestine?

Kidney: metabolic acidosis -; glutaminase ; glutamate dehydrogenase forms NH3

a-ketogluterate -; gluconeogenesis


Intestine: catabolism


what is the problem? result?

Cystine re-uptake in kidney;leads to kidney stones


what’s the problem? result?



defect in cystine t/p out of lysosome

leads to cystine crystals in lysosomes



kidney failure


poor growth

Rx: cysteamine slows progress

what’s Hartnup’s disease?


t/p for large aa’s defect

Trp deficiency results in higher requirement for niacin to avoid pellagra

what are 2 uses for polyamines?

what two diseases is it associated with?

so how would you treat it?

they’re (-) charged so used in DNA packing

also in NMDA & AMPA receptor in the brain

polyamine hypersynthesis: seen in cancer & sleeping sickness

Rx: target the Ornithine decarboxylase (1st step in polyamine synth)

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