Amino Acid Metabolism EC Flashcards
Nitrogen containing substances are used in the synthesis of what compounds?
Nucleotides Neurotransmitters Hormones Porphyrins Nonessential amino acids
What are the essential amino acids?
Phenylalanine Valine Tryptophan Threonine Isoleucine Methionine Histidine Leucine Lysine
Which amino acids are acidic?
Aspartate
Glutamate
Tremor, slurred speech, somnolence, vomiting, cerebral edema, and blurred vision
Ammonia intoxication
Liver disease or urea cycle enzyme deficiency
NH4 accumulates and depletes a-ketoglutarate (blocks TCA)
What happens to carbon skeletons of amino acids after the ammonia has been removed?
They are degraded and become intermediates in the TCA cycle
Some are ketogenic: Lysine & Leucine
Some are both: Isoleucine, Phenylalanine, Typrtophan, & Tyrosine
Some are glucogenic: rest
Tyrosine derivatives
Thyroid hormones
DOPA (dopamine, NE/Epi, melanin)
Methionine
S-Adenosylmethionine (SAM) - methyl group transfers
Homocysteine
Cysteine
Tryptophan
Niacin
Serotonin
Melatonin
Glutamate
GABA
Glutathione
Glycine
Porphyrin (heme)
Arginine
Creatine
NO
Urea
Histidine
Histamine
Phenylalanine
Tyrosine (dopa, thyroid hormones)
What does phenylalanine hydroxylase do?
Convert Phenylalanine to Tyrosine
Man presents with knee and back pain. Dark spots on conjunctiva and nasal bridge. Urine turns dark if forgets to flush.
Alkaptonuria
Defective homogentisic acid oxidase (degrades tyrosine)
Tyrosine, Phenylalanine, and Homogentisic acid build up
Presents to ER with sudden severe, intermittent right flank pain w/ n/v. Urinalysis shows hematuria. Kidney stones with cysteine crystals found.
Cystinuria
Defective transport of Cysteine, Ornithine, Arginine, & Lysine “COAL”
Cystosis - intralysosomal accumulation of cysteine
Fanconi Syndrome
Renal proximal tubule dysfunction (hypophosphatemia, glycosuria, amino aciduria, hypokalemia)
Growth retardation, rickets, polyuria, dehydration, metabolic acidosis, photophobia.
Man complaining of photosensitive rash on face and neck and extensor surfaces. Has been feeling more irritable than normal and is somewhat ataxic. Eats healthy with a well balanced diet.
Hartnup disease
Mutation in neutral a.a. transporter
Tryptophan excreted in urine and not absorbed in gut
Leads to niacin deficiency-pellagra
7 yo boy presents complaining of diminished visual acuity. On p/e, lenticular dislocation found along with abnormally long fingers. Has mild mental retardation. Labs reveal elevated serum methionine and urine homocysteine.
Homocystinuria
Defects: Cystathionine synthase (or PP/B6 cofactor affinity). Homocysteine methyltransferase
Homocysteine accumulates-
toxic to vascular endothelium (atherosclerosis),
interferes with collagen formation (ocular/skeletal)
4 day old infant presents because vomiting and urine smells sweet. Moro reflex absent and rigid. Labs show metabolic acidosis.
Maple Syrup Urine Disease
Defect in BCKD (branched chain ketoacid dehydrogenase)
Diminished breakdown of Isoleucine, Leucine, & Valine
“I Love Vermont Maple Syrup”
Ketoacids toxic to brain
Branched chain a.a.’s in urine lead to sweet smell
2 y/o blonde haired blue eyes immigrant presents with possible developmental delays. Hypertonia and hyperreflexia and smells “musky”. Guthrie test positive, phenylketones in urine.
PKU (phenylketonuria)
Defect in Phenylalanine Hydroxylase or tetrahydrobiopterin cofactor (converts phenylalanine to tyrosine)
Phenylalanine buildup causes brain damage (and becomes deficient in tyrosine derivatives)
Avoid foods w/ phenylalanine (aspartame)
