AA Catabolism

Question 1

describe the biochemical defect in PKU

Answer 1

Question 2

the most severe IQ decline seen in PKU patients is in ______ (timeline)

Answer 2

the most severe IQ decline seen in PKU patients is in the first few days

Question 3

describe the treatment of PKU

Answer 3

• avoidance of phenylalanine
• sapropterin (synthetic form of BH4) may be used in some PKU patients
  
  • typically mild or moderate forms of the disease

Question 4

describe maternal PKU syndrome

Answer 4

• women with PKU must maintain low Phe levels before conception and during pregnancy
  
  • strict adherence must be maintained prior to conception and throughout preg.
• high maternal blood Phe leads to fetal defects
  
  • micrcephaly
  • lack of mental dev.
  • congenital heart defects
• elevated Phe levels has teratogenic properties

Question 5

describe alkaptonuria pathway

Answer 5

Question 6

alkaptonuria is caused by a deficiency in ____

Answer 6

alkaptonuria is caused by a deficiency in homogentisic acid oxidase

Question 7

_____ accumulates in alkaptonuria

Answer 7

homogentisic acid accumulates in alkaptonuria

Question 8

describe tyrosinemia type I aka tyrosinosis

Answer 8

• deficiency of fumaryl acetoacetate hydrolase
• build up of fumaryl-acetoacetate
  
  • metabolized to another compound that causes kidney and liver damage
    
    • cabbage like odor of the urine

Question 9

contrast the urine in PKU, alkaptonuria, maple syrup urine disease and tyrosinemia type I

Answer 9

PKU = mousey odor of urine

alkaptonuria = black/brown discoloration of urine (due to homogentisic acid)

maple syrup urine disease = maple syrup odor of urine

tyrosinemia type I = cabbage like smell to urine

Question 10

describe the biochemical pathway defect in MSUD

Answer 10

Question 11

_____ is deficient in maple syrup urine disease

Answer 11

branched chain alpha-keto acid dehydrogenase

Question 12

describe treatment of MSUD

Answer 12

• dietary restriction of branched chain amino acids–leucine, isoleucine, valine
• dietary supplementation with TPP (vit. B1) may be useful in patients that have an enzyme with low coenzyme affinity

Question 13

describe methylmalonyl CoA mutase deficiency

Answer 13

• results in elevated levels of methylmalonic acid (MA) in circulation
• causes metabolic acidosis due to the accumulation of MA
• associated with neurological manifestations, seizures, encephalopathy

Question 14

in some children with methylmalonyl CoA mutase deficiency, there is improvemetn with _____ supplementation

Answer 14

in some children with methylmalonyl CoA mutase deficiency, there is improvemetn with vit. B12 (cobalamin) supplementation

Question 15

describe the methylmalonyl CoA mutase deficiency pathway

Answer 15

Question 16

describe homocystinuria

Answer 16

• deficiency of cystathionine B-synthase (transulfuration pathway)
• a group of disorders in which there is a defect in homocysteine metabolism
• characterized by high plasma and urinary levels of homocysteine
• homocysteine binds to connective tissue and disrputs structure
  
  • characterized by dislocation of lens, skeletal abnormalities, delay of mental dev
• some patients respond to oral vit. B6

Question 17

homocystinuria is caused by a deficiency in ______

Answer 17

homocystinuria is caused by a deficiency in cystathionine B-synthase

Question 18

describe the pathway of homocystinuria

Answer 18

Question 19

what are two potential fates of homocysteine?

Answer 19

methionine and cysteine