MMT: amino acid catabolism III Flashcards
What does phenylalanine hydroxylase do?
Convert phenylalanine to tyrosine
What coenzyme does phenylalanine hydroxylase use?
BH4
What does homogentisate oxidase do?
Convert homogentisate to maleylacetoacetate
What does fumarylacetoacetate do?
Convert fumarylacetoacetate to acetoacetate and fumarate
What is phenylketonuria?
A defect in either phenylalanine hydroxylase or dihydrobiopterin reductase leads to a buildup of phenylalanine and phenyl ketones
What does dihydrobiopterin reductase do?
Regenerates BH4
What will happen in a buildup of phenyl alanine?
An aminotransferase will break it into phenyl ketones phenylacetate and phenyllactate
What are signs of phenylketonuria?
Hypopigmentation (no tyrosine = no melanin) and musty body odor
How do we treat phenylalanine hydroxylase defect?
Decreased phenylalanine intake and increased tyrosine intake
How do we treat dihydrobiopterin reductase defect?
Supplementation of BH4 (tetrahydrobiopterin)
What is alkaptonuria?
Homogentisate oxidase defect leads to a buildup of homogentisate
What are signs of alkaptonuria?
Urine turns black when exposed to air, dark pigment in connective tissue, arthritis risk
How do we treat alkaptonuria?
High dose vitamin C or nitisinone
What is tyrosinemia I?
Fumarylacetoacetate hydrolase leads to a buildup of fumarylacetoacetate
What are symptoms of tyrosinemia?
Cabbage-like odor
How do we treat tyrosinemia?
Nitisinone
Valine is… (ketogenic vs glucogenic)
Glucogenic; forms propionyl CoA
Isoleucine is… (ketogenic vs glucogenic)
Both! Forms propionyl CoA and acetyl CoA
Leucine is… (ketogenic vs glucogenic)
Ketogenic; forms acetoacetate
What is branched-chain a-ketoacid dehydrogenase?
Converts valine, isoleucine, and leucine carbon skeletons into CoA derivatives
What cofactor does branched-chain a-ketoacid dehydrogenase use?
TPP
What is maple syrup urine disease?
Defect in branched chain a-ketoacid dehydrogenase
What is the main symptom of maple syrup urine disease?
Urine smells like maple syrup
How do we treat maple syrup urine disease?
Limit intake of branched-chain amino acids; we can’t take them out completely because they’re essential
