Lecture 4: Amino Acid Metaboism Flashcards
What amino acids are ketogenic only?
Leu and Lys
- Leu can go to both acetoacetate and acetyl CoA, Lys can just go to acetoacetate
What are Ketogenic amino acids precursors for?
Ketone bodies and fatty acids
Where does the formation and degradation of ketone bodies occur?
Liver
What amino acids are both ketogenic and glucogenic?
Ile, Trp, Phe, Tyr, Thr
What TCA intermediate can Glu be converted to?
Alpha ketoglutyrate
What TCA intermediate do Phe and Tyr get converted to?
Fumarate
Phe -> Tyr -> Fumarate
Where is the major location of Transaminase reactions, specifically ALT and AST?
Liver and the muscle
- If these organs were to be diseased these enzymes would make it into the blood -> this can be diagnostic for liver or muscle (skeletal and cardiac)
What amino acids is alanine aminotransferase responsible for transaminating?
Pyruvate + Glutamate -> Alanine + Alpha ketoglutarate
What amino acids is aspartate aminotransferase responsible for transaminatiing?
Oxaloacetate + glutamate -> Aspartate + alpha ketoglutarate
What amino acid is an important carrier for Ammonia?
Glutamate/glutamine
- Ammonia is toxic to neuro tissue so glutamate ability to pick up ammonia is a protection mechanism. In the liver it will be trapped in urea and excreted in the kidney it will be trappped in urine
What causes homocystinuria?
1) Cystathionine beta synthase defect
2) Vitamin deficiencies (B6, 12, folic acid)
What are the branched chain amino acids?
Leu, Val, Ile
- They are hydrophobic and all essential
What causes maple syrup urine disease?
Decreased branched chain alpha-keto acid dehydrogenase complex (BCKD) activity
- Maple syrup urine disease is autosomal recessive
What is the hallmark maple syrup smell in newborns with maple syrup urine disease?
Branched-chain ketoaciiduria
How is maple syrup urine disease treated?
Synthetic diet low in BCAAs and BCKD activity can be restored with thiamine supplementation in mild forms
What causes Phenylketonuria (PKU)?
Defects in PAH activity -> The enzyme that converts Phe to Tyr
What is the most common inborn error of metabolism?
PKU
What causes albinism?
Tyrosinase defect causing a lack of melanin
How is hyperthyroidism treated?
With drugs that block iodination of thyroglobulin -> this decreases the production of thyroid hormones T4 and T3
Pyridoxal 5’ phosphate, folic acid and vitamin B12 all may help lower what?
Homocysteine levels
Where are urea cycle enzymes located?
Liver
Ammonia is removed as _____ from the brain
Gln
Nitrogen is removed as _____ from muscle
Ala
Urea secreted in urine from __________
Kidney
