Sulfur-containing amino acid metabolism — Flashcards

Flashcard 1: S-adenosylmethionine (SAM) donates a CH3 group to anabolic pathways, forming _____

Answer: S-adenosylhomocysteine

Flashcard 2: _____ disease is characterized by neutral aminoaciduria and decreased neutral AA absorption (esp. tryptophan) from the gut

Answer: Hartnup

Flashcard 3: Homocystinuria can be caused by _____ deficiencies.

Answer: vitamin (B6, B9, or B12)

Extra: Classic homocystinuria is most commonly caused by an autosomal recessive deficiency of cystathionine beta-synthase (CBS). However, elevated homocysteine (and subsequent homocystinuria) can also be caused by deficiencies in B6 (pyridoxine), B9 (folate), or B12 (cobalamin).

Flashcard 4: Cystine is made of two _____ amino acids connected by a disulfide bond

Answer: cysteine

Flashcard 5: Vitamin B12 and folate deficiency result in mildly elevated _____ levels, increasing risk for thrombosis

Answer: homocysteine

Flashcard 6: Folate deficiency is characterized by _____ serum homocysteine

Answer: increased

Flashcard 7: What stainable protein is abundant in astrocytes?

Answer: GFAP

Flashcard 8: What enzyme converts pyruvate to alanine?

Answer: alanine aminotransferase (ALT)

Flashcard 9: Role of myeloperoxidase in neutrophils:

Answer: Plays a role in respiratory burst (catalyzes formation of HOCl from H2O2)

Extra: Myeloperoxidase (MPO) is found in the azurophilic granules of neutrophils (PMNs). During the respiratory burst, it converts Hydrogen Peroxide (H2O2) and Chloride ions into Hypochlorous acid (HOCl - bleach), which is a potent bactericidal agent.

Flashcard 10: What reaction is catalyzed by superoxide dismutase during the respiratory burst?

Answer: Conversion of Superoxide ($O_2^-$) to Hydrogen peroxide ($H_2O_2$)

Extra: Superoxide dismutase (SOD) neutralizes superoxide radicals. Reaction: 2O2- + 2H+ -> H2O2 + O2. Clinical Pearl: Mutations in superoxide dismutase 1 (SOD1) are associated with Amyotrophic Lateral Sclerosis (ALS).