Lectures 33-34: Amino Acid Metabolism

Question 1

What enzyme is involved in the transamination reaction of amino acid to form glutarate (step 1) during formation of ammonium ion?

Answer 1

Aminotransferase

Question 2

What reaction occurs as nitrogen is liberated from an amino acid to become free ammonium ion (step 2)?

Answer 2

Deamination

Question 3

Where does the urea cycle occur?

Answer 3

The liver

Question 4

Ketogenic amino acids

Answer 4

Give rise to ketone bodies or fatty acids; degraded to Acetyl CoA or Acetoacetyl CoA

Question 5

Which amino acids are STRICTLY ketogenic?

Answer 5

Leucine, lysine

Question 6

Glucogenic amino acids

Answer 6

Give rise to glucose and have metabolic fates within the TCA cycle - all amino acids are glucogenic except leucine and lysine

Question 7

Which amino acids are both glucogenic and ketogenic?

Answer 7

phenylalaine, tryptophan, tyrosine, isoleucine

Question 8

Which amino acids are metabolically fated to pyruvate?

Answer 8

Alanine, cysteine, glycine, serine, threonine, tryptophan

Question 9

Which amino acids are metabolically fated to oxaloacetate?

Answer 9

Asparagine, aspartate

Question 10

Which amino acids are metabolically fated to fumarate?

Answer 10

aspartate, phenylalanine, tyrosine

Question 11

Which amino acids are metabolically fated to succinyl-CoA?

Answer 11

Isoleucine, methionine, threonine, valine

Question 12

Which amino acids are metabolically fated to alpha ketoglutarate?

Answer 12

arginine, glutamine, glutarate, histidine, proline

Question 13

Which amino acids are metabolically fated to Acetyl CoA?

Answer 13

Isoleucine, leucine, tryptophan

Question 14

Which amino acids are metabolically fated to Acetoacetyl CoA?

Answer 14

Leucine, lysine, phenylalanine, tryptophan, tyrosine

Question 15

What is the rate determining step in heme synthesis?

Answer 15

Conversion of Succinyl CoA and glycine to delta aminolevulinate via Ala-synthase enzyme

Question 16

Where does the rate determining step of heme synthesis occur?

Answer 16

Mitochondria

Question 17

Where do all other reactions of heme synthesis occur (besides rate determining step)?

Answer 17

Cytosol

Question 18

Acute intermittent porphyria is associated with which enzyme of heme synthesis?

Answer 18

Porphobilinogen deaminase

Question 19

Congenital erythropoeitic porphyria is associated with which enzyme of heme synthesis?

Answer 19

Uroporphyrinogen III synthase, cosynthase

Question 20

What are some physical conditions associated with porphyrias?

Answer 20

Skin problems, nervous/neuropsychiatric problems

Question 21

What are the products of heme degradation?

Answer 21

Biliverdin which is converted to indirect/unconjugated bilirubin

Question 22

What enzyme is responsible for converting unconjugated bilirubin to bilirubin?

Answer 22

UDP Glucuronide Transferase

Question 23

What is the ultimate fate of bilirubin?

Answer 23

Excreted in urine as urobilinogen or feces as circobilin

Question 24

What is the amino acid precursor of Sphingosine?

Answer 24

Serine

Question 25

What is the amino acid precursor of Histamine?

Answer 25

Histidine

Question 26

What is the amino acid precursor of Thyroxine?

Answer 26

Tyrosine

Question 27

What is the amino acid precursor of Epinephrine?

Answer 27

Tyrosine

Question 28

What is the amino acid precursor of Serotonin?

Answer 28

Tryptophan

Question 29

What is the amino acid precursor of Nicotinamide?

Answer 29

Tryptophan

Question 30

From which amino acid does nitric oxide (NO) arise?

Answer 30

Arginine

Question 31

Neuronal Nitric Oxide Synthase (nNOS)

Answer 31

Expressed in neurons, produces NO as a neurotransmitter/signal to brain

Question 32

Inducible Nitric Oxide Synthase (iNOS)

Answer 32

Expressed in immune system, produces NO as a “killer” compound (sends out free radicals)

Question 33

Endothelial Nitric Oxide Synthase (eNOS)

Answer 33

Vasodilator, relaxes smooth muscle in vessels

Question 34

What molecule is required for the synthesis of nitric oxide from arginine?

Answer 34

BH4 (tetrahydrobiopterin)

Question 35

PKU

Answer 35

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

Question 36

What are the amino acid components of glutathione?

Answer 36

1. Gamma-glutarate
2. Cysteine
3. Glycine

Question 37

What is the function of glutathione?

Answer 37

Antioxidant which detoxifies lipid radicals and hydrogen peroxide