7B-Synthesis/Degredation of AA's Flashcards
What amino acids are considered to be essential?
PVT TIM HALL. Phe, Val, Trp, Thr, Ile, Met, His, Arg, Leu, Lys
Which AA’s are strictly ketogenic?
Leu and Lys
Which AA is essential for growth only in children?
Arg
Why is tetrahydrofolate needed for AA synthesis?
FH4 is used to transfer one-carbon groups at various oxidation states
FH4 is used in AA degradation (serine and histidine)
FH4 is used in biosynthesis: glycine serine
Why is BH4 needed for AA synthesis?
BH4 is used for hydroxylation reactions (phenylalanine and tyrosine)
What is the cause and Sx of Gly Metabolism disorder?
Lack of transaminase that converts glyoxylate –> glycine
Glycine is metabolized to glyoxylate.
Glyoxylate can be oxidized to Oxalate, which is not very soluble and can precipitate with Ca in the kidneys causing stones
What is the cause of cystaionuria?
Defect in cystathionase
Deficiency in Vitamin B6 (PLP).
What are the clinical manifestations of homocystinuria?
Cardiovascular disease/atherosclerosis (peroxiadtion of LDL), defective collagen synthesis, brain szrs/mental retardation.
What is the cause of homocystinuria?
Primary: defect in cystathionine synthase (rare)
Secondary: deficiency in Vitamin B6, B12, or Folic Acid (more common)
What is the cause and Sx of cystinuria?
Manifestation: Kidney Stones
Cause: a defect in the cystine transporter located in both the intestinal and renal cells.
What is the cause and Sx of cystinosis?
Cause: a defect in the cystine transporter located in lysosomal membranes.
cystine crystals accumulate in lysosomes, disturb their function, and cause renal failure.
What is the cause of maple syrup urine disease?
Caused by a deficiency in a-keto dehydrogenase activity, a deficiency in thiamine can accelerate this disorder (alcoholics).
What are the Sx of maple syrup urine disease?
Manifestation: urine smells like maple syrup or burnt sugar
Ketoacidosis, and neurologic complications
What are the Sx of PKU?
Manifestation: Accumulated phenylalanine and phenylketones are neurotoxic and lead to mental retardation
this inhibits the neuronal uptake of tyrosine & tryptophan, which are needed as neurotransmitter substrates and inhibits myelination of nerves
What is the cause of PKU?
Cause: deficiency in Phenylalanine Hydroxylase activity, which may be due to:
one of 170 mutations in the PAH gene
deficiency in BH4 synthesis
deficiency in BH4 reductase activity
What is the cause of alcaptonuria?
Cause: defect is in the enzyme Homogentisate Oxidase, therefor homegentisate accumulates and autooxidizes.
oxidized homogentisate makes urine black
binds and hyperpigments connective tissues and joints (ochronosis) resulting in arthritic joint pain
What are the Sx and cause of tyrosinemia I?
Manifestation: liver failure and early death
Cause: defective Fumarylactoacetate Hyrdolase
What are the Sx and cause of tyrosinemia II?
Manifestation: eye and skin lesions, & neurological problems
Cause: defective Tyrosine Aminotransferase
What are the nonessential AA’s that can be made from intermediates of glycolysis?
Glycine, Serine, Cysteine and Alanine (Ala is major gluconeogenic AA) are all non-essential AA that can be formed from intermediates during glycolysis.
What 5 amino acids can be made form a-KG?
Glutamate, Glutamine, Proline, Arginine, Histidine
What 2 amino acids can be made from OAA?
Aspartate, Asparginine
What 3 amino acids can be made form fumerate?
Aspartate, Phenylalanine, Tyrosine
What 4 amino acids can be made from succinyl CoA?
Methionine, Threonine, Valine, Isoleucine
What 6 amino acids can be made from pyruvate?
Threonine, Glycine, Tryptophan, Alanine, Serine, Cysteine
what are some causes and Sx of homocystinuria?
disorders in the metabolism of homocysteine
inherited as autosomal recessive
high plasma and urinary levels of homocysteine and methionine and low levels of cysteine
defect in cystathionine β-synthase is the most common cause of homocystinuria
homozygotes exhibit ectopia lentis (displacement of the lens of the eye), skeletal abnormalities, premature arterial disease, osteoporosis, and mental retardation.
treatment includes restriction of methionine intake and supplementation with vitamins B6, B12, and folate.
how can vitamin deficiencies in folate vitamin B12 or vitamin B6 can lead to homocysteinuria?
Folate provides FH4
Vitamin B6 provides PLP
Vitamin B12 is used as B12
