Metabolism

Question 1

A. Defect in Cyststhionine Synthase is called what?
B. What vitamin does cystathionine synthase require?
C. What accumulates and where?
D. What happens to methionine levels?
E. What are 4 clinical presentations?
F. What is the treatment?

Answer 1

A. Homocystinuria
B. B6
C. Homocysteine accumulates in the urine
D. Methionine is elevated in the blood
E. 1. mental retardation 2. dislocation of the lens
3. Osteoporosis 4. Myocardial infarction
F. High doses of B6, B9, & B12, methionine restriction

Question 2

What are the branched-chain amino acids?

1. Deficiency of the Branched-chain α-keto acid dehydrogenase is called what?
2. What accumulates and where?
3. What are the clinical presentation and mortality rates?
4. What is the treatment?

Answer 2

Lucine, Isoleucine, & Valine

1. Maple Syrup Urine Disease
2. branch chain amino acids and keto analogs accumulate in the plasma and urine
3. Neurological problems. The mortality rate is high
4. Restriction of dietary intake of branched-chain amino acids

Question 3

1. Deficiency in what causes Methylmalonic Acidemia?
2. What accumulates?
3. What is the treatment?
4. What drugs should be avoided?
5. What 3 other things should be avoided?

Answer 3

1. Methylmalonyl CoA Mutase
2. Methylmalonic acid accumulates
3. Adenosyl-cobalamin for patients who cannot synthesize this coenzyme. Restriction of dietary protein for everyone else
4. Avoidance antibiotics during acute crisis.
5. avoidance of stress, fasting & low-carb diets

Question 4

1. Propionyl-CoA Carboxylase deficiency causes what?

2. How does the patient present?

Answer 4

1. Propionic Acidemia
2. Recurrent episodes of metabolic acidosis, neurologic
   complications.

Question 5

1. What enzyme is deficient in Phenylketonuria
2. What odor do babies present with?
3. What is the treatment?

Answer 5

1. Phenylalanine hydroxylase is deficient
2. Mousy order
3. A low-phenylalanine diet normalizes mental development in children, recommended life-long.

Question 6

1. What causes hyperphenylalaninemia?

2. Which neurotransmitters are reduced?

Answer 6

1. dihydropteridine reductase deficiency

2. catecholamines and serotonin formation are reduced

Question 7

1. A block of Homogentisate oxidase causes what?
2. What will the urine look like?
3. What happens to the vertebrae and what does it cause?

Answer 7

1. Alkaptonuria
2. Darkening at the surface (after 15 minutes). Urine becomes black after 2 hours
3. Black pigment deposits in cartilage, causing arthritis in elderly patients.

Question 8

Name 2 causes of albinism

Answer 8

A deficiency in tyrosinase ( unable to convert tyrosine to DOPA which prevents the formation of dopaquinone which is required to form melanin).
Albinism can also be caused by a deficiency of a
transporter in the melanosome membrane.

Question 9

1. What enzyme is deficient in Histidinemia?
2. What accumulates after an oral histidine load?
3. What happens to blood and urine?

Answer 9

1. Histidase
2. FIGlu accumulates
3. Blood and urine have elevated levels of histidine

Question 10

1. What is creatine?

2. Why should oral supplements of creatine be avoided?

Answer 10

1. Creatine phosphate is an energy store in muscle, used for short-term vigorous contraction.
2. Oral carnitine is metabolized to trimethylamine (gut bacteria) and trimethylamine oxide (liver). May
   have harmful cardiovascular effects.