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