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Biochemistry > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

Source of METHYL groups in metabolism

PRECURSOR of CYSTEINE

A

METHIONINE

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2
Q

Synthesized from methionine and ATP

A

S- ADENOSYLMETHIONINE (SAM)

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3
Q

Enzymes involved in metabolism of sulfur containing amino acid

A 
Methiobine adenosyl transferase
Methyl transferase
Adenosyyl homocysteinase
Methionine synthase
Cystathionine B synthase
Cystathionase
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4
Q

After donating its methyl group SAM is converted to

A

S-ADENOSYLHOMOCYSTEINE

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5
Q

Catecholamines are inactivated (catabolized) by

A

MONOAMINE OXIDASE (MAO) and CATECHOL O METHYLTRANSFERASE (COMT)

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6
Q

NE and Epi are degraded to

A

VANILLYMANDELIC ACID (VMA)

increased in pheochromocytoma

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7
Q

Dopamine is degraded to

A

HOMOVANILLIC ACID (HVA)

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8
Q

DOPA Decarboxylase

A

L-DOPA – DOPAMINE

COFACTOR - B6 (pyridoxine)

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9
Q

Dopamine beta hydroxylase

A

DOPAMINE – NOREPINEPHRINE

COFACTOR: VITAMIN C

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10
Q

The MC metabolic disorder concerned w/ amino acid

A

Classic Phenylketonuria

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11
Q

Biochemical defect in PKU

A

PHENYLALANINE HYDROXYLASE DEFICIENCY

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12
Q

Phenylalanine hydroxylase

A

L PHENYLALANINE –> L TYROSINE

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13
Q

Phenylalanine hydroxylase

A

L PHENYLALANINE –> L TYROSINE

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14
Q

Phenylketonuria

ACCUMULATION OF PHENYLKETONES
phenylpyruvate (characteristic odor to the urine)
phenyllactate
phenylacetate

A 
mental retardation
musty odor
vomiting
hyperactive with autistic behavior
lighter in their complexion than unaffected siblings
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15
Q

The main organ affected by hyperphenylalaninemia

A

BRAIN

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16
Q

Treatment of Classical PKU

A

Dietary control to DECREASE PHENYLALANINE AND INCREASE TYROSINE

AVOID:
HIGH protein foods - meat, dairy, nuts, legumes

starches - bread, potatoes, corn and beans

ALLOWED
LOW protein foods - fruits, nonstarchy vegetables

17
Q

Congenital deficiency of HEMOGENTISATE OXIDASE in the degradative pathway of tyrosine –> build up of HOMOGENTISIC ACID

A

ALKAPTONURIA

18
Q

Alkaptonuria

A

alkapton bodies –> urine turn black on standing

dark CT (OCHRONOSIS)

benign disease but may have DEBILITATING ARTHRALGIAS

pigment deposition

19
Q

GARRODS TETRAD

A

Alkaptonuria
Albinism
Pentosuria
Cystinuria

20
Q

Treatment for alkaptonuria

A

aimed at reducing pigment deposition

reduce phenylalanine and tyrosine

VITAMIN C

21
Q

Defective melanin synthesis from TYROSINE

A

ALBINISM

absence of copper requiring enzyme TYROSINASE

defective tyrosine transporters

22
Q

Specialized products from TYROSINE

A

MELANIN
CATECHOLAMINES
THYROXINE

23
Q

Type I Tyrosinemias

A

FUMARYL ACETOACETATE HYDROLASE DEFICIENCY

cabbage like odor

24
Q

Type II Tyrosinemia

A

TYROSINE TRANSAMINASE DEFICIENCY

25
Q

MC inborn error of methionine metabolism

A

Classic Homocystinuria

26
Q

Enzyme deficient in Homocystinuria

A

CYSTATHIONINE B SYNTHASE

COENZYME: Pyridoxal phosphate

27
Q

Defect in methionine degradation leads to

A

HIGH PLASMA AND URINARY LEVELS OF HOMOCYSTEINE AND METHIONINE

LOW LEVELS OF CYSTEINE

28
Q

Homocystinuria

A

normal at birth

3 y/o - subluxation of the ocular lens (ECTOPIA LENTIS) – severe myopua and iridodonesis (quivering of the iris)
displacement is DOWNWARD

progressive INTELLECTUAL DISABILITY

SKELETAL ABNORMALITIES - tall, thin, w/ elongated limbs, arachnodactyl, pectus excavatum or carinatum, genu valgum, pes cavus

THROMBOEMBOLIC EPISODES - both large and small vessels

  • MI
  • stroke in the young
29
Q

Diagnostics of Homocystinuria

A

ELEVATIONS - methionine and homocystine (or homocysteine)

LOW - cystine in the plasma

30
Q

Treatment of Homocystinuria

A

Restriction of Methionine

  • limit eggs, fish and meat
  • encourage protein from plant foods (soya, nuts)

Supplementation with vitamins B6, B12 and folate

31
Q 
Inherited defect of renal tubular amino acid transporter for (COLA)
CYSTINE
ORNITHINE
LYSINE
ARGININE
A

CYSTINURIA

excess cystine in urine –> precipitation if cystine kidney stones and staghorn calculi

32
Q

Treatment for Cystinuria

A

ACETAZOLAMIDE - alkalinize the urine

33
Q

Defect in the conversion of methylmalonyl CoA to succinyl CoA

Involves metabolism of AA that ate converted to propionyl CoA:
ISOLEUCINE, VALINE, THREONINE and METHIONINE

A

METHYLMALONIC ACIDEMIA

seizure, encephalopathy, stroke at the age of 1 month to 1 year

34
Q

Treatment for Methylmalonic Acidemia

A

Protein Restricted diet (0.5 - 1.5 g/kg/d with L carnitine and cobalamin supplementation

35
Q

Blocked degradation of branched amino acids (ISOLEUCINE, VALINE, LEUCINE!!) d.t. deficiency in alpha ketoacid dehydrogenase complex

A

MAPLE SYRUP URINE DISEASE

vomiting, seizures, mental retardation

36
Q

Treatment for Maple Syrup Urine Disease

A

Dietary restriction

Limit intake of valine, isoleucine and leucine

37
Q

Affected infants who are normal at birth develop poor feeding and vomiting in the 1st week of life

lethargy, coma, convulsions

metabolic acidosis

hypertonicity, muscular rigidity with severe opisthonos

A

Maple Syrup Urine Disease

38
Q

Function of Histamine and Receptor Responsible for its Action

A

H1 - smooth muscle contraction; increased vascular permeability

H2 - gastric HCL secretion

H3 - synthesis and release of histamine in the brain

39
Q

Metabolic error d.t. deficiency of HISTIDASE

histidase - converts HISTIDINE to UROCONATE

A

HISTIDINEMIA

autosomal recessive
benign

Biochemistry (75 decks)

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