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CC LEC > Metabolism Of Amino Acids > Flashcards

Metabolism Of Amino Acids Flashcards

1
Q

Amino acids (especially essential amino acids) are found in food in the form of_____

A

protein

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2
Q
  1. From the food, protein is ingested
  2. Protein will be initially digested by the enzymes ______ (2)
    ○ Once degraded = amino acids are created
  3. Amino acids will be absorbed in the intestine and will become part of the________
    ■ Where amino acids are acquired to be used for translation
  4. Once the body opts to degrade the amino acid, the product of degradation will vary depending on if the amino acid is _______ (2)
A

pepsin and trypsin

amino acid pool

ketogenic or glucogenic

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3
Q

Rare, inherited disorders of amino acid metabolism

A

AMINOACIDOPATHIES

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4
Q
  • Abnormalities in activity of a specific enzyme in the metabolic pathway
  • Abnormalities in the membrane transport system for amino acids
A

AMINOACIDOPATHIES

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5
Q

AMINOACIDOPATHIES

PTAMCHICA

A

PHENYLKETONURIA

TYROSINEMIA

ALKAPTONURIA

MAPLE SYRUP DISEASE

CITRULLINEMIA

HOMOCYSTINURIA

ISOVALERIC ACIDEMIA (IVA)

CYSTINURIA

ARGININOSUCCINIC ACIDURIA

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6
Q

autosomal recessive trait

Total absence of activity of
PHENYLALANINE HYDROXYLASE

  • Catalyzes the conversion of phenylalanine to tyrosine
A

PHENYLKETONURIA (PKU)

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7
Q
  • Catalyzes the conversion of phenylalanine to tyrosine
A

PHENYLALANINE HYDROXYLASE

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8
Q

Children
- Retarded mental development
• Occurs as a result of the toxic effects of the brain of phenylpyruvate or one of its metabolic by-products

A

Pku

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9
Q

Pku

2nd or 3rd week of life
•_______ - deamination of phenylalanine
•_______ - decarboxylation and oxidation of phenylpyruvate
•_______ - glutamine conjugate of phenylacetate

A

Phenylpyruvate

Phenylacetic acid

Phenylacety|glutamine

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10
Q

PKU

METHODS OF DETERMINATION

A

Guthrie Bacterial Inhibition Assay

Microfluorometric assay

High-Performance Liquid Chromatography (HPLC)

Urine test

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11
Q

• Spores of Bacillus subtilis are incorporated into an agar plate that contains beta-2-thienylalanine (antagonist)

• Filter paper disk impregnated with blood from the infant is placed on the agar

• If blood phenylalanine exceeds
3-4 mg/dL, phenylalanine counteracts the antagonist and bacterial growth occurs

A

Guthrie Bacterial Inhibition Assay

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12
Q

Guthrie Bacterial Inhibition Assay

• Spores of Bacillus subtilis are incorporated into an agar plate that contains_______(antagonist)
• Filter paper disk impregnated with blood from the infant is placed on the agar
• If blood phenylalanine exceeds
_____, phenylalanine counteracts the antagonist and bacterial growth occurs

A

beta-2-thienylalanine

3-4 mg/dL

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13
Q

• direct measurement of phenylalanine in dried blood filter disks

• Based on the fluorescence of a complex formed of
phenylalanine-ninhydrin-copper in the presence of a dipeptide (L-leucvl-L-alanine)

• Excitation/emission wavelengths of 360 nm and 530 nm respectively

A

Microfluorometric assay

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14
Q

Microfluorometric assay

• direct measurement of phenylalanine in dried blood filter disks
• Based on the fluorescence of a complex formed of
______in the presence of a dipeptide (L-leucvl-L-alanine)
• Excitation/emission wavelengths of________ respectively

A

phenylalanine-ninhydrin-copper

360 nm and 530 nm

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15
Q

Pku

  • Reference method
  • Newborn: 1.2 - 3.4 mg/dL (70-200 umol/L)
A

High-Performance Liquid Chromatography (HPLC)

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16
Q

Pku

  • monitoring
  • Reagent strip test
    • Involves the reaction of ferric chloride with phenylpyruvic acid in urine to produce a green color
A

Urine Test

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17
Q

Urine Test for PKU

  • monitoring
  • Reagent strip test
    • Involves the reaction of ferric chloride with phenylpyruvic acid in urine to produce a_____
A

green color

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18
Q

• Characterized by excretion of tyrosine and tyrosine catabolites in urine

A

TYROSINEMIA

19
Q

Deficiency in:
- Fumarylacetoacetate (FAA) hydrolase (type I)
4-hydroxy-phenylpyruvic acid oxidase (type Il)
- tyrosine aminotransferase (type III)

A

TYROSINEMIA

20
Q

COMPLICATIONS: Leads to liver damage (Cirrhosis and liver cancer)

A

TYROSINEMIA

21
Q

• Familial inheritance
• Lack of homogentisate oxidase

A

ALKAPTONURIA

22
Q

• Lack of homogentisate oxidase

• Accumulation of HGA

A

Alkaptonuria

23
Q
  • accumulates in connective tissue causing generalized pigmentation of these tissues (Ochronosis), an arthritis-like degeneration
  • Characterized by darkening of urine
A

Alkaptonuria

24
Q

Characterized by burnt sugar odor of the urine, breath, and skin

A

MAPLE SYRUP URINE DISEASE

25
Q

Lack of branched-chain alpha-ketoacid decarboxylase
- Blocking the normal metabolism of: Leu, Ile and Val

A

MSUD

26
Q

MSUD Diagnosis

A

• Modified Guthrie test : 4-azaleucine
• Microfluorometric assay : Leucine dehydrogenase

27
Q

MSUD

• Microfluorometric assay : Leucine dehydrogenase

_______is indicative of MSUD

A

above 4 mg/dL

28
Q

COMPLICATIONS:
Lethargy, failure to thrive, Muscle rigidity, Respiratory irregularities, Mental retardation, Convulsions, Acidosis and hypoglycemia

A

MSUD

29
Q

• Deficiency of isovaleryl-CoA dehydrogenase in leucine pathway

A

ISOVALERIC ACIDEMIA

30
Q

• “sweaty feet” odor

A

Isovaleric acidemia

31
Q

HOMOCYSTINURIA

•________
- Intermediate amino acid in the synthesis of cysteine from methionine

A

Homocysteine

32
Q

• Impaired activity of cystathionine beta-synthase (homocysteine to cvsteine)

A

Homocystinuria

33
Q

HOMOCYSTINURIA

Diagnostic tests

A

Cyanide-Nitroprusside Urine Spot Test

Silver-nitroprusside Test

34
Q

Homocystinuria

  • Cysteine and homocysteine are reduced by sodium cyanide to free-thiol
  • Then, reacted to sodium nitroprusside to produce a red-purple color
A

Cyanide-Nitroprusside Urine Spot Test

35
Q

Cyanide-Nitroprusside Urine Spot Test

Positive indicator of homocystinuria

A

Red purple

36
Q
  • Confirmation for homocysteine
    • Silver nitrate reduces homocysteine to form reddish color
A

• Silver-nitroprusside Test

37
Q

• Silver-nitroprusside Test positive indicator of homocystinuria

A

Reddish color

38
Q

COMPLICATIONS:
- Thromboembolism, Cardiovascular risk, Atherosclerotic disease, Low folate concentrations, Vitamin B12 deficiency

A

Homocystinuria

39
Q

• Results from inherited enzyme deficiencies in the urea cycle

A

CITRULLINEMIA

40
Q

CITRULLINEMIA

:
- lack of the enzyme argininosuccinic acid synthetase (ASS)

:
- caused by a mutation of the gene that would provide instructions for making the protein citrin
- inhibits the urea cycle and disrupts the production of proteins and nucleotides

A

• Type 1

• Type 2

41
Q

COMPLICATIONS: Vomiting, high ammonia levels and Mental retardation

A

Citrullinemia

42
Q

• Results from inherited enzyme deficiencies in the urea cycle

• Deficiency in argininosuccinate lyase (ASL)

  • prevents the conversion of argininosuccinic acid into arginine

• COMPLICATIONS:
- Vomiting, high ammonia levels and Mental retardation

A

ARGININOSUCCINIC ACIDURIA

43
Q

• a defect in the amino acid transport system rather than a metabolic enzyme deficiency

• Increased urinary excretion of cystine
- Resulting from genetic defect in the renal resorptive mechanism

A

CYSTINURIA

44
Q
  • Cystine
    • Insoluble
    • Tends to precipitate in the kidney tubules
  • Urinary calculi
A

Cystinuria

CC LEC (38 decks)

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