Protein Biochemistry

Question 1

S-adenosylmethionine (SAM)

Answer 1

• Energy source
• Methyl donor other rxns
• Precursor for homocysteine => vascular disease and wound healing
• Involved in B12 and folate metabolism

Question 2

Sulfur-containing aa

Answer 2

1. Cysteine

2. Methionine

Question 3

Glutathione

Answer 3

• Tri-peptide containing cysteine

* Important: redox buffer, protects against free radical

Question 4

Aromatic-ring-containing aa

Answer 4

1. Tryptophan
2. Phenylalanine
3. Tyrosine

Question 5

Disease caused by defect in enzymes breaking down branched chain aa

Answer 5

Maple Syrup Urine Disease

Question 6

Importance of aromatic aa

Answer 6

Precursor for:

1. Serotonin
2. Niacin
3. Dopamine
4. Epi/NE
5. Tetrahydrobiopterine
6. Thyroid hormone

Question 7

Name Ketogenic aa (2)

Answer 7

Start with “L”

1. Leucine
2. Lysine

Question 8

Name aa participate in both Ketogenic and Glucogenic (4)

Answer 8

IsoL goes both ways
Others have rings
think NT precursors
1. Tyrosine
2. Isoleucine
3. Phenylalanine
4. Tryptophan

Question 9

Why vit C important for the formation of collagen?

Answer 9

• Collagen comprised of hydroxyproline (Hyp) and hydroxylysine (Hyl)
• Prolyl hydroxylase converts Pro –> Hyp
• Lysyl hydroxylase converts Lys –> Hyl
  => Both enzymes require vit C as coenzyme

Question 10

Post-translational modifications (3)

Answer 10

1. Phosphorylation:
   * Most common
   * On OH group of serine, threonine, tyrosine
2. Hydroxylation
   * On proline and lysine
   * Important for collagen formation
3. Carboxylation
   * addition carboxylic acid onto glutamic acid –> carboxyglutamate (Gla)
   * catalyzed by glutamyl carboxylase
   * vit K dependent