urea cycle

Question 1

AA catabolism is done by

Answer 1

urea cycle formation of common metabolites (pyruvate, acetyl-CoA) for metabolic fuels

• excess nitrogen generated by urea cycle converted to urea and excreted by kidneys

Question 2

Arginase deficiency presents as

Answer 2

• progressive spastic diplegia
• abnormal movements
• growth delay
• increased arginine levels
• mild or no hyperamonemia

Question 3

How to treat arginase deficiency

Answer 3

• low protein diet
• give synthetic protein w/only essential AA

Question 4

Arginase makes

Answer 4

urea and ornithine

Question 5

What is ornithine transcarbamylase deficiency d/t

Answer 5

XR

interferes with body’s ability to eliminate ammonia

excess carbamoyl phosphate converted to orotic acid

Question 6

Findings with OTC deficiency

Answer 6

• increased orotic acid in blood and urine
• decreased BUN
• symptoms of hyperamonemia
• no megaloblastic anemia (vs. orotic aciduria)

Question 7

in ornithine transcarbamylase deficiency you cannot make

Answer 7

citrulline

increased ornithine and carbamoyl phosphate, orotic acid

Question 8

Biochemical cause of hyperammonemia symptoms

Answer 8

increased NH3 depletes glutamate in CNS = inhibits TCA cycle (decrease alpha-ketoglutarate)

Question 9

What does lactulose do to decrease ammonia levels

Answer 9

acidfies GI tract to trap NH4+ for excretion

Question 10

How do antibiotics (rifamiximin, neomycin) decrease ammonia levels

Answer 10

decrease ammoniagenic bacteria

Question 11

How does benzoate, phenylacetate, or phenylbutyrate help with high ammonia levels

Answer 11

react with glycine or glutamine forming products that are excreted renally