Lecture 4: Amino Acid Metaboism

Question 1

What amino acids are ketogenic only?

Answer 1

Leu and Lys

• Leu can go to both acetoacetate and acetyl CoA, Lys can just go to acetoacetate

Question 2

What are Ketogenic amino acids precursors for?

Answer 2

Ketone bodies and fatty acids

Question 3

Where does the formation and degradation of ketone bodies occur?

Answer 3

Liver

Question 4

What amino acids are both ketogenic and glucogenic?

Answer 4

Ile, Trp, Phe, Tyr, Thr

Question 5

What TCA intermediate can Glu be converted to?

Answer 5

Alpha ketoglutyrate

Question 6

What TCA intermediate do Phe and Tyr get converted to?

Answer 6

Fumarate

Phe -> Tyr -> Fumarate

Question 7

Where is the major location of Transaminase reactions, specifically ALT and AST?

Answer 7

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)

Question 8

What amino acids is alanine aminotransferase responsible for transaminating?

Answer 8

Pyruvate + Glutamate -> Alanine + Alpha ketoglutarate

Question 9

What amino acids is aspartate aminotransferase responsible for transaminatiing?

Answer 9

Oxaloacetate + glutamate -> Aspartate + alpha ketoglutarate

Question 10

What amino acid is an important carrier for Ammonia?

Answer 10

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

Question 11

What causes homocystinuria?

Answer 11

1) Cystathionine beta synthase defect

2) Vitamin deficiencies (B6, 12, folic acid)

Question 12

What are the branched chain amino acids?

Answer 12

Leu, Val, Ile

• They are hydrophobic and all essential

Question 13

What causes maple syrup urine disease?

Answer 13

Decreased branched chain alpha-keto acid dehydrogenase complex (BCKD) activity

• Maple syrup urine disease is autosomal recessive

Question 14

What is the hallmark maple syrup smell in newborns with maple syrup urine disease?

Answer 14

Branched-chain ketoaciiduria

Question 15

How is maple syrup urine disease treated?

Answer 15

Synthetic diet low in BCAAs and BCKD activity can be restored with thiamine supplementation in mild forms

Question 16

What causes Phenylketonuria (PKU)?

Answer 16

Defects in PAH activity -> The enzyme that converts Phe to Tyr

Question 17

What is the most common inborn error of metabolism?

Answer 17

PKU

Question 18

What causes albinism?

Answer 18

Tyrosinase defect causing a lack of melanin

Question 19

How is hyperthyroidism treated?

Answer 19

With drugs that block iodination of thyroglobulin -> this decreases the production of thyroid hormones T4 and T3

Question 20

Pyridoxal 5’ phosphate, folic acid and vitamin B12 all may help lower what?

Answer 20

Homocysteine levels

Question 21

Where are urea cycle enzymes located?

Answer 21

Liver

Question 22

Ammonia is removed as _____ from the brain

Answer 22

Gln

Question 23

Nitrogen is removed as _____ from muscle

Answer 23

Ala

Question 24

Urea secreted in urine from __________

Answer 24

Kidney

Question 25

What is the most at risk organ in the accumulation of ammonia?

Answer 25

Brain

Question 26

Is NH3 or NH4 more toxic?

Answer 26

NH3 is the toxic agent due to its ability to permeate membranes