Lectures 33-34: Amino Acid Metabolism Flashcards
What enzyme is involved in the transamination reaction of amino acid to form glutarate (step 1) during formation of ammonium ion?
Aminotransferase
What reaction occurs as nitrogen is liberated from an amino acid to become free ammonium ion (step 2)?
Deamination
Where does the urea cycle occur?
The liver
Ketogenic amino acids
Give rise to ketone bodies or fatty acids; degraded to Acetyl CoA or Acetoacetyl CoA
Which amino acids are STRICTLY ketogenic?
Leucine, lysine
Glucogenic amino acids
Give rise to glucose and have metabolic fates within the TCA cycle - all amino acids are glucogenic except leucine and lysine
Which amino acids are both glucogenic and ketogenic?
phenylalaine, tryptophan, tyrosine, isoleucine
Which amino acids are metabolically fated to pyruvate?
Alanine, cysteine, glycine, serine, threonine, tryptophan
Which amino acids are metabolically fated to oxaloacetate?
Asparagine, aspartate
Which amino acids are metabolically fated to fumarate?
aspartate, phenylalanine, tyrosine
Which amino acids are metabolically fated to succinyl-CoA?
Isoleucine, methionine, threonine, valine
Which amino acids are metabolically fated to alpha ketoglutarate?
arginine, glutamine, glutarate, histidine, proline
Which amino acids are metabolically fated to Acetyl CoA?
Isoleucine, leucine, tryptophan
Which amino acids are metabolically fated to Acetoacetyl CoA?
Leucine, lysine, phenylalanine, tryptophan, tyrosine
What is the rate determining step in heme synthesis?
Conversion of Succinyl CoA and glycine to delta aminolevulinate via Ala-synthase enzyme
Where does the rate determining step of heme synthesis occur?
Mitochondria
Where do all other reactions of heme synthesis occur (besides rate determining step)?
Cytosol
Acute intermittent porphyria is associated with which enzyme of heme synthesis?
Porphobilinogen deaminase
Congenital erythropoeitic porphyria is associated with which enzyme of heme synthesis?
Uroporphyrinogen III synthase, cosynthase
What are some physical conditions associated with porphyrias?
Skin problems, nervous/neuropsychiatric problems
What are the products of heme degradation?
Biliverdin which is converted to indirect/unconjugated bilirubin
What enzyme is responsible for converting unconjugated bilirubin to bilirubin?
UDP Glucuronide Transferase
What is the ultimate fate of bilirubin?
Excreted in urine as urobilinogen or feces as circobilin
What is the amino acid precursor of Sphingosine?
Serine
What is the amino acid precursor of Histamine?
Histidine
What is the amino acid precursor of Thyroxine?
Tyrosine
What is the amino acid precursor of Epinephrine?
Tyrosine
What is the amino acid precursor of Serotonin?
Tryptophan
What is the amino acid precursor of Nicotinamide?
Tryptophan
From which amino acid does nitric oxide (NO) arise?
Arginine
Neuronal Nitric Oxide Synthase (nNOS)
Expressed in neurons, produces NO as a neurotransmitter/signal to brain
Inducible Nitric Oxide Synthase (iNOS)
Expressed in immune system, produces NO as a “killer” compound (sends out free radicals)
Endothelial Nitric Oxide Synthase (eNOS)
Vasodilator, relaxes smooth muscle in vessels
What molecule is required for the synthesis of nitric oxide from arginine?
BH4 (tetrahydrobiopterin)
PKU
Defect in conversion of phenylalanine to tyrosine leading to build up of phenylketones and brain damage
Type I: Enzyme defective
Type II: Inability to make BH4
What are the amino acid components of glutathione?
- Gamma-glutarate
- Cysteine
- Glycine
What is the function of glutathione?
Antioxidant which detoxifies lipid radicals and hydrogen peroxide
