AA Degradation And Biosynthesis

Question 1

Non ketotic hyperglycinemia

Answer 1

Glycine encephalopathy

• caused by def of glycine cleavage pathway
• blood glycine increased
• neuro conditions bc of increased glycine–>inhibitory NT

Question 2

Primary hyperoxaluria

Answer 2

Def of transaminase in liver peroxisomes

-causes overproduction of oxalate which leads to stones in the kidney causing kidney damage

Question 3

PKU

Answer 3

Major type due to def of phenylalanine hydroxylase due to def of dihydrobiopterin reductase

• tyrosine becomes essential AA
• musty (mousey) odor

Question 4

Tyrosinemia Type I

Answer 4

Def of fumaryl acetoacetate hydrolase

• cabbage like body odor
• early death due to liver failure
• renal impairment

Question 5

Alkaptonuria

Answer 5

Def of homogentisate oxidase
-black diaper syndrome
-homogentisate excreted in urine
Large joint arthritis 
-

Question 6

Albinism

Answer 6

Increased phenylalanine inhibits tyrosinase

-partial or complete absence of melanin from the skin

Question 7

Homocystinuria

Answer 7

Def of cystathionine beta synthase

• increased plasma homocysteine and excreted in urine
• plasma methionine increased
• ectopia lentis
• osteoporosis
• some patients respond to vitamin B6 therapy

Question 8

Cystinuria

Answer 8

• excretion of COAL—cysteine, ornithine, arginine, and lysine
• causes kidney stones
• transport protein meant for reabsorption of these AA is defective in renal tubules

Question 9

Cystathonuria

Answer 9

Benign

• common in preemies
• def of cystathionase
• could be def of B6 bc enzyme requires PLP

Question 10

Maple syrup urine disease

Answer 10

Def of branched chain alpha keto acid dehydrogenase

• elevation of branches chain aa and this corresponding keto acids in plasma
• neuro probs
• severe ketoacidosis
• urine smells like maple syrup
• mate respond to thiamine therapy since enzyme requires TPP

Question 11

Hartnup disease

Answer 11

Defect in absorption of tryptophan from GI and defective reabsorption from kidney

• results in def of tryptophan
• pellagra like sx
• pellagra is the def sx of niacin
• niacin is partly synthesized from tryptophan

Question 12

Propionyl carboxylate def

Answer 12

Propionic acidemia/aciduria

-vomiting, lethargy, ketosis, hypotonia, seizures and intolerance to protein

Question 13

Methylmalonic acidemia

Answer 13

Def of methylmalonyl CoA mutase

• MM acid is increased in plasma and excreted in urine
• metabolic acidosis and developmental abnormalities
• could be treated with B12

Question 14

Non-ketotic hyperglycinemia

Answer 14

Glycine encephalopathy

• def of glycine cleavage system
• blood glucose