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25 Cards in this Set

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What is required for Phenylalanine degradation?
-Phe Hydrolxylase
-O2
-5,6,7,8-Tetrahydrobiopterin
-Dihydrobiopterin Reductase
-NADH
What kind of enzyme is Phenylalanine Hydroxylase?
Mixed function monooxidase
How much of the cofactor THBP is required? Why?
Catalytic amts - b/c it is recycled by the reductase enzyme.
What does Phenylalanine hydroxylase deficiency cause?
Classic Phenylketonuria (PKU)
What is the freq of classic PKU?
Treatment?
1/20,000
-Low protein diet, Tyrosine supplements
What causes PKU type IV?
Dihydrobiopterin deficiency
Why is PKU bad?
Because accumulation of Phenylalanine is toxic to the brain.
Which is more severe; PKU classical or Type IV?
Type IV - because the reductase enzyme is used in other pathways.
What are the 2 enzymes that break down Tyrosine?
1. Tyrosine Aminotransferase
2. p-Hydroxyphenylpyruvate Dioxygenase
What does deficiency of Tyrosine Aminotransferase cause?
Tyrosinemia Type II
What are the characteristics of Tyrosinemia Type II?
-Erosions of cornea, palm, nad soles
What does deficiency of p-Hydroxyphenylpyruvate Dioxygenase cause?
Tyrosinemia Type III
What are the characteristics of Tyrosinemia Type III?
Asymptomatic - usually benign.
Why is Tyrosinemia Type III benign?
Because p-Hydroxyphenylpyruvate can be excreted as organic acid so its excess doesn't hurt.
What is the product of p-Hydroxyphenylpyruvate dioxygenase?
Homogentisate
What causes Alkaptonuria?
Deficiency of Homogentisate 1,2-Dioxygenase
What causes urine to turn dark in Alkaptonuria?
The homogentisic acid excreted in urine forms a dark pigment in Oxygen under basic conditions.
What is the product of Homogentisate 1,2-Dioxygenase?
Maleylacetoacetate
What enzyme acts on Maleylacetoacetate, and what is the product?
Maleylacetate isomerase - makes Fumarylacetoacetate
What enzyme acts on Fumarylacetoacetate?
Fumarylacetoacetase - cleaves the molecule into Fumarate and Acetoacetate
What does deficiency of Fumarylacetoacetate cause?
Tyrosinemia Type I - the most severe form.
What is the only treatment for Tyrosinemia Type I?
Liver transplant, otherwise death within first two years of life.
What drug is given to postpone liver transplants in Tyrosinemia Type I?
2-nitro-4-trifluoromethyl 1,2 cyclohexadione.
How does this drug alter the disease state?
Inhibits hydroxyphenylpyruvate dioxygenase, so the precursor is excreted as organic acids
What does tyrosinemia type I become when the drug is given?
Type III - benign tyrosinemia