Amino Acid Metabolism

Question 0

AA derived from TCA cycle intermediates?

Answer 0

Oxaloacetate is interchangeable with aspartate which is interchangeable with asparagine. Alphaketoglutarate is exchangeable with glutamate. Glutamate can mAke proline and Arginine. Glutamate is also exchangeable with Glutamine

Question 1

AA derived from glycolysis?

Answer 1

Glucose goes to 3-phosphoglycerate which goes to 2 -phosphoglycerate (serine in between), which goes to puruvate which goes to Alanine and is reversible. Serine can reversibly make glycine and serine can make cystine which can be made into puruvate

Question 2

Cystinuria

Answer 2

Inherited mutations (autosomal recessive) in amino acid carrier for cystine and basic AAs. Cystine precips, forming kidney stones.

Question 3

Maple Syrup Urine Disease

Answer 3

Alpha-ketoacid dehydrogenase- Does oxidative decarboxylation-
Classic: 1 wk infant, convulsions, vomiting, maple syrup odor urine
Labs: Elevated plasma & Urine Val, ISO, Leu, ketoacids, hypoglycemic, ketoacidosis
Treatment: hydration, transfusion, synthetic low BCAA diet- thiamine supplements for intermittent and mild

Question 4

Phenylketonuria (PKU)

Answer 4

Defect: phenyalanine hydroxylase- phenylalinine accumulates in blood and brain
Symptoms: infants develop seizures, cognitive delay, light complexion, mousy odor
Treatment: phenylalinine restricted diet
- In US all infants screened at birth

Question 5

Tyrosinemia (type II)

Answer 5

Defect: tyrosine aminotransferase
Patients: plaques on hands and feet, corneal ulcers & frequent mental retardation
Labs: serum tyrosine elevated (20-50 mg/dL) (normal=1-4 mg/dL)
Treatment: synthetic diet, low phenylalanine, low tyrosine

Question 6

Alcaptonuria

Answer 6

Deficient: homogentisate oxidase
Patients: asymptomatic until middle age - then: arthritis, back pain, renal calculi - kidney stone
-homogentisate accumulates & is excreted, giving urine dark color
Diagnosis: -Homogentisic acid in urine
-Ochronosis (dark spots of polymerized Homogentisic acid in sclera & ear cartiledge)

Question 7

Tyrosinemia (type I)

Answer 7

Disorder: fumaryloacetate hydrolase (FAH)
-results in accumulation of succinylacetone which can cause liver failure
Symptoms: acute, hepatic crisis (2-4 months), hypoglycemia, elevated AST&ALT, jaundice, hepatomegaly
Diagnosis: succinylacetone in urine and blood
Treatment: Nitisinone (also limit phenylalanine & tyrosine)