Amino acid catabolism

BIOCHEMISTRY 3(2+1)
Lesson 25 : Amino Acid Metabolism

Amino acid catabolism

  1. Excess amino acids (those not used for protein synthesis or synthesis of other macromolecules) cannot be stored.
  2. Surplus amino acids are used as metabolic fuel.
  3. ? -amino group is removed; carbon skeleton is converted into major metabolic intermediate
  4. Amino group converted to urea; carbon skeletons converted into acetyl CoA, acetoacetyl CoA, pyruvate, or citric acid intermediate.
  5. Fatty acids, ketone bodies, and glucose can be formed from amino acids.
  6. Major site of amino acid degradation is the liver.
  7. First step is the transfer of ?-amino group to ?-ketoglutarate to form glutamate, which is oxidatively deaminated to yield NH4+.(Figure1 & Figure2)
  8. Some of NH4+ is consumed in biosynthesis of nitrogen compounds; most terrestrial vertebrates convert NH4+ into urea, which is then excreted (considered ureotelic).
  9. Terrestrial reptiles and birds convert NH4+ into uric acid for excretion (considered uricotelic).
  10. Aquatic animals excrete NH4+ (considered ammontelic).
  11. In terrestrial vertebrates NH4+ is converted to urea via urea cycle.
  12. One of nitrogen atoms in urea is transferred from aspartate; other is derived from NH4+; carbon atom comes from CO2.
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Last modified: Monday, 30 January 2012, 7:07 AM