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MCM Quiz 1 > AA metabolism > Flashcards

AA metabolism Flashcards

1
Q

Where do free amino acids come from?

A
  • .Protein turnover
  • .Digested food
  • .De novo synthesis**
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2
Q

How are amino acids used?

A

Production of body protein
Synthesis of nitrogen-containing compounds
Degradation

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3
Q

What is hartnup disease? what happens?

A

Defective transport of nonpolar or neutral amino acids (e.g. Tryptophan) leads to concentrated level in the urine.

protein transporters mediate transport of amino acids in and out of cells, kidney and SI

failure to thrive, nystagmus, tremor, intermittent ataxia and photosensitivity.

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4
Q

Cystinuria?

A

Defective transport of dimeric cystine and dibasic amino acids Arg, Lys, and ornithine

Formation of cystine crystals in the kidneys (renal calculi)

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5
Q

How are aromatic aa made?

A

Phe- Tyr

Rib5P- His

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6
Q

How is ala made?

A

Pyruvate to ala

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7
Q

how is aspartate made?

A

oxaloacetate to asp to asn

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8
Q

how is glutamate made?

A

aketo to glutamate

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9
Q

what are Proteolytic enzymes?

A

degradation of proteins for reabsorption, exo and endo

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10
Q

what does Exopeptidase do?

A

attacks at C- (carboxypeptidase) or N-terminus

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11
Q

what does Endopeptidase do ?

A

attacks within the protein at a specific site.

mechanism of action which is dependent on the catalytic enzyme in the active site

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12
Q

what are the 3 intracelluar protein degradation pathways?

A

Proteasome, lysosome and autophagosome

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13
Q

Lysosomal /Autophagy? what is it

A

nonselective, active at pH5

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14
Q

What does proteosome do?

A

large proteasome cytoplasmic complexes that cleave polyubiquinated proteins ubiquitin pathway

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15
Q

how does Extracellular Proteolytic Control work?

A

enzymes secreted as needed

Secreted as inactive zymogens, activated by proteolytic cleavage

trypsinogen activated by enterokinase

activates chemotrypsinogen

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16
Q

What role do enteropeptidases play in protein digestion?

A

They are membrane-bound intestinal proteins

They are serine proteases

Convert the zymogen trypsinogen to active trypsin

.Allows trypsin to convert other zymogens to active forms

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17
Q

What are the ketogenic aa?

A

Leu, Lys

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18
Q

What are the ketogenic and glutogenic aa?

A

Ile trp, phe, tyr,thr

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19
Q

What does Trp become in TCA cycle?

A

Pyruvate

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20
Q

What does Lys become in TCA?

A

acetoacetate

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21
Q

What contributes to GLU in TCA cycle?

A

Gln, His, Arg

22
Q

What are the three cycles of how aa are metabolized?

A
  1. transaminase
  2. glutamate dehydrogenase
  3. urea cycle
23
Q

what is transamination? what happens?

A
  • Amino group is transferred to an α-ketoacid
  • Coupled reactions
  • Enzymes called transaminases/aminotransferases
24
Q

What are the three most important transaminase reactions?

A

pyruvate + glutamate—- (alanine transferase/ alt)— alanine+ aketo

oxalo +glutamate— (aspartate aminotransferase/ ast)—- asp + aketo

glutamine +h2o—- (glutamine aminohydrolase/GA)—- glutamate + nh3

25
Q

Transaminases, what do they require?

A

(PLP)– Derivative of Vitamin B6

26
Q

What is homocysteinemia?

A

Met to homocysteine issue , homocysteine methyltransferase nt working , vitamin deficiency

27
Q

What is homocystinuria?

A

cystathionine β-synthase not working, met to homocysteine

28
Q

what are the consequences of homocysteinemia and homocystinuria?

A

Four organ systems: eye, skeletal, CNS, vascular

29
Q

What do BCAs metabolize to?

A

Val and ILe become succincyl CoA

Leu become acetyl CoA

30
Q

what is maple syrup disease? what happens?

A

issues with metabolizing BCA

urine give the hallmark maple syrup smell.

accumulate in blood causing toxic effects on brain function and eventually mental retardation

31
Q

What is Phe metablized into, what enzyme and whats the significance?

A

Phe to Tyr (phenylalanine hydroxylase)

Phenylketonuria happens here

32
Q

What is PKU caused by?

A

defects in the activity of phenylalanine hydroxylase (PAH)

Secondary PKU resulting from tetrahydrobiopterin deficiency

Phe instead converted to phenylpyruvte and then to phenyllactate

33
Q

What is an important Ser derivative?

A

Acetylcholine

34
Q

Important Trp derivatives?

A

Serotonin, Niacin, needs b6!

35
Q

Important Tyr derivatives

A

Dopamine, thyroid, melanin

36
Q

Important Glu derivatives

A

Gaba

37
Q

important arginine derivatives

A

Arg, Gly,Met

Creatine phosphate, kidney dysfunction means higher blood levels

38
Q

What is albinism, how does it occur?

A

Tyrosine to melanin is blocked due to defective tyrosinase

39
Q

Where do thyroid hormones come from?

A

Come from Tyr, need iodine (graves disease and stuff)

hyperthyroidism patients treated with iodine, decrease T4 and T3

40
Q

What are the two ways Nitrogen can be removed?

A

As ammonia, Glu and Gln in brain, gln and ala in other tissues

As urea

41
Q

How is NH4 removed from brain?

A

aKG to GLU to GLN (this process requires ATP and NADPH)

then, Gln becomes Glu again, makes NH4 which goes to urea cycle

42
Q

How is NH4 removed in muscle?

A

Glucose becomes pyruvate which is turned into Ala, Ala goes to liver, becomes pyruvate which releases NH4

This NH4 enters urea cycle

In liver, Ala goes to pyruvate via ALT, aKG to Glu via GLDH, NH4 produced

*Alt used to convert pyruvate to Ala

43
Q

What is the rate limiting step of the urea cycle

A

NH4 to carbamoyl phophate via carbamoyl synthetase

44
Q

When is urea produced in urea cycle?

A

When Arg becomes orthinine via arginase

45
Q

When can hyperammonemia occur?

A

NH4—carbamyol phosphate

ornithine—-citrulline

46
Q

when can citrullemia occur?

A

citrulline—argininosuccinate (as synthetase)

47
Q

when can arginosuccinate aciduria occur?

A

arginosuccinate—arg (arginosuccinate lyase)

48
Q

what is ammonia toxicity?

A

NH3 is a toxic agent

pH imbalance ,

Glutamate dehydrogenase catalyzes of glutamate to a-ketoglutarate, a key reactant in the TCA cycle; this inhibits the activity of the TCA cycle

Depletion of glutamate, depletion of neurotransmitter activity

49
Q

Urea cycle and the high protein diet , correlation?

A

urea production is increased by a high protein diet and decreased by high carb diet

Provides a source of ammonia nitrogen for gut bacteria, salvage and reuse

50
Q

Creatine, relevance?

A

Synthesized from Arg, Gly, Met

Cardioselective isoform of creatine kinase (CK-MB) can serve as a diagnostic for myocardial infarction

non-enzymatically converted from creatine phosphate to creatinine

indicative for kidney dysfunction and muscle degeneration

MCM Quiz 1 (9 decks)

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