Tyrosine, Phenylalanine Flashcards
What enzyme converts phenylalanine to tyrosine?
Phenylalanine hydroxylase
What cofactor is required for the conversion of phenylalanine to tyrosine?
Tetrahydrobiopterin (BH4)
A deficiency in phenylalanine hydroxylase leads to which metabolic disorder?
Phenylketonuria (PKU)
Which enzyme is responsible for converting tyrosine to homogentisic acid?
Tyrosine aminotransferase
What metabolic disorder results from homogentisic acid oxidase deficiency?
Alkaptonuria
What is the main pigment derived from tyrosine metabolism?
Melanin
Which hormone is synthesized from tyrosine and regulates metabolism?
Thyroxine (T4)
Tyrosine is a precursor for which neurotransmitters?
Dopamine, Norepinephrine, Epinephrine
What enzyme converts DOPA to dopamine?
DOPA decarboxylase
A defect in fumarylacetoacetate hydrolase causes which disorder?
Tyrosinemia type I
Which metabolic disorder results in dark urine upon standing due to homogentisic acid accumulation?
Alkaptonuria
Which disorder is treated with a low-phenylalanine diet and supplementation of tyrosine?
Phenylketonuria (PKU)
What is the role of dihydropteridine reductase in tyrosine metabolism?
Regenerates tetrahydrobiopterin (BH4)
Which amino acid becomes essential in PKU?
Tyrosine
What toxic metabolite accumulates in tyrosinemia type I?
Succinylacetone
Which enzyme deficiency is associated with neonatal tyrosinemia?
p-Hydroxyphenylpyruvate dioxygenase
Which pathway is impaired in phenylketonuria (PKU)?
Phenylalanine to tyrosine conversion
Which metabolic disorder is associated with a musty body odor?
Phenylketonuria (PKU)
What is the treatment for alkaptonuria?
High-dose Vitamin C and dietary protein restriction
Which enzyme converts dopamine to norepinephrine?
Dopamine β-hydroxylase
Which enzyme converts norepinephrine to epinephrine?
Phenylethanolamine N-methyltransferase
Which cofactor is required for the conversion of tyrosine to DOPA?
Tetrahydrobiopterin (BH4)
Which laboratory finding is characteristic of alkaptonuria?
Darkened urine upon exposure to air
What is the main cause of neurological impairment in PKU?
Accumulation of phenylalanine and its neurotoxic derivatives
