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Biochemistry Final Review > Ford (Amino Acid Catabolism) > Flashcards

Ford (Amino Acid Catabolism) Flashcards

1
Q

Protein Sources: Diet (3)

A
  1. Stomach –> low pH denatures proteins/activates pepsin
  2. Small Intestine - enteropeptidase (cleave trypsinogen), Aminopeptidase (exopeptidases, chew from N-term), Dipeptidase (break apart dipeptides)
  3. AA, dipeptides, tripeptides transported into cells
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2
Q

Protein Sources: Intracellular

A
  • 2 structures: proteasome/lysosome
  • N-term AA identity determines ubiquitination rate
  • cytosolic proteases degrade peptides –> leave pool of AA
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3
Q

Proteasome

A
  • ATPase (20s = catalytic domain, 19s = regulatory domain)

- S stands for Svedberg Units = NOT proportional to size

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4
Q

Deamination

A
  • separate -NH3 from C –> leaving behind carbon skeletons
  • 2 enzyme mechanism = Aminotransferase + Glutamate Dehydrogenase
  • serine/threonine deaminated by dehydratase
  • Pyridoxal Phosphate always coenzyme
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5
Q

Direct Deamination (Serione/Threonine ONLY)

A
  • remove water = dehydration
  • adds water back to remove NH4 = deamination

Serine –> pyruvate
Threonine –> a-ketobutyrate

deamination through glutamate = NH4

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6
Q

Two Special Aminotransferases

A
  1. Aspartate Aminotransferase (SGOT)
    • aspartate –> oxaloacetate
    • aspartate/a-ketoglutarate = oxaloacetate/glutamate
  2. Alanine Aminotransferase (SGPT)
    • alanine –> pyruvate
    • alanine/a-ketoglutarate = pyruvate/glutamate
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7
Q

Deamination Steps (2)

A
  1. aminotransferase makes glutamate
  2. glutamate dehydrogenase releases ammonium ion
    • glutamate –> Schiff-base –> a-ketoglutarate
    • generates NADPH, regenerate a-ketoglutarate

regenerate pieces needed to continue deamination

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8
Q

Urea Cycle Importance

A
  • NH4 toxic biproduct of AA catabolism

- NH4 converted to urea in liver, which is transported to kidney to be excreted from body

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9
Q

Urea Cycle Step 1

A
  • CO2 + NH4 = carbamoyl phosphate in mitochondria
    • carbomoyl phosphate synthetase I (CPSI)
    • uses 2 ATP

COMMITTED STEP IN UREA CYCLE

  • N-acetylglutamate activates CPSI (NAG: allosteric act)
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10
Q

Urea Cycle Step 2

A
  • Ornithine (moves into mitochondria) + carbamoyl phosphate = Citrulline
    • ornithine transcarbamoylase
  • citrulline exported to cytoplasm
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11
Q

Urea Cycle Step 3

A
  • aspartate donates NH3 + citrulline = argininosuccinate
    • argininosuccinate synthetase
  • argininosuccinase –> arginine + fumarate
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12
Q

Aspartate Regeneration

A

fumarate –> malate –> oxaloacetate –> aspartate

  • fumarate –> oxaloacetate uses TCA cycle
  • oxaloacetate –> aspartate via SGOT aminotrans.
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13
Q

Urea Cycle Step 4

A
  • ornithine created when urea removed from arginine
  • water addition when cleaving arginine adds final O of urea
  • ornithine into mitochondria –> continue cycle
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14
Q

Fates of Carbon Skeletons (3)

A

Ketogenic: degraded into intermediate molecules that can be create KETONE BODIES

Glucogenic: degraded into intermediate molecules that can feed through GLUCONEOGENESIS to reform GLUCOSE

Ketogenic and Glucogenic: AA degraded to more than one possible molecule

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15
Q

AAs converted to Pyruvate (5)

A

Glucogenic

Serine, Threonine, Glycine, Alanine, Cysteine

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16
Q

AAs converted to Oxaloacetate (2)

A

Glucogenic

Asparagine, Aspartate –> oxaloacetate (via SGOT)

17
Q

AAs converted to a-ketoglutarate (5)

A

Glucogenic

Glutamine, Proline, Arginine, Histidine, Glutamate

18
Q

AAs converted to Succinyl-CoA (3)

A

Glucogenic

  1. Methionine, Valine

Both

  1. Isoleucine
19
Q

AAs converted to Fumarate (3)

A

Glucogenic

  1. Aspartate

Both

  1. Tyrosine
  2. Phenylalanine
20
Q

AAs converted to Acetyl-CoA (3)

A

Ketogenic

  1. Leucine

Both

  1. Threonine
  2. Isoleucine
21
Q

AAs converted to Acetoacetate (5)

A

Ketogenic

  1. Leucine
  2. Lysine

Both

  1. Tryptophan
  2. Phenylalanine
  3. Tyrosine
22
Q

Ketogenic ONLY amino acids

A

leucine and lysine

23
Q

Both Ketogenic and Glucogenic amino acids

A

isoleucine, phenylalanine, threonine, tryptophan, tyrosine

Biochemistry Final Review (8 decks)

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