AAs as Metabolic Precursors, Phenylketonurias Flashcards
Hyperphenylalaninemias are caused by what?
defects in metabolism of aromatic AAs
Phenylketonuria is most commonly cause by defects in ___________
phenylalanine hydroxylase
what is nitric oxide derived from?
arginine
what is GABA derived from?
glutamate
phenylalanine hydroxylase
converts phenylalanine –> tyrosine, req tetrahydrobiopterin
what other pathways is stimulated when phenylalanine hydroxylase is blocked?
minor fates of phenylalanine, like formation of phenylpyruvate (a ketone) = phenylketone formation
possible causes of phenylketonuria
(1) mutation/deficiency of phenylalanine hydroxyls
(2) mutation/deficiency of enzyme that synthesizes or reduces coenzyme biopterin
active form of biopterin
tetrahydrobiopterin
what rxns/enzymes is tetrahydrobiopterin an cofactor for?
(1) Phenylalanine –> tyrosine (phenylalaine hydroxylase)
(2) tyrosine –> DOPA - becomes catecholamines (tyrosine hydrolase)
(3) tryptophan –> 5HT - becomes serotonin (tryptophan hydrolase)
GTP cyclohydrase, Dihydrobiopterin synthetase
enzyme that synthesizes biopterin from GTP
dihydrobiopterin reductase
enzyme that reduces biopterin
what is DOPA derived from?
derived from tyrosine; hyperphenylalanine cause pigmentation defects by reducing melanin synthesis (b/c buildup of tyrosine)
what is serotonin derived from? what is it’s phys role?
synth from tryptophan; run req tetrahydrobiopterin
- phys role: SM contraction, pain perception, behavior
how is histamine synthesized? Function?
Synth: from decarboxylation of AA histidine
Function: wide range of cellular responses - allergic, inflammatory, gastric acid secretion
how is GABA synth? function?
Synth: decarboxylation of glutamate
Function: major inhibitory neurotransmitter
