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29 Cards in this Set

  • Front
  • Back
components of heme
Fe2+ and protoporphyrin IX
where is most heme synthesized
in erythroid tissues - Not mature red cells because they have already lost their mitochondria
formation of aminolevulinic acid (ALA)
glycine and succinyl-CoA condense to form ALA via ALA synthase
what two things inhibit ALA synthase and where are they found respectively
Heme - ALAS1 (liver)
Iron - ALAS2 (erythroid cell)
what causes increased synthesis of ALA in the liver
administration of any drug that results in CYP450 activation and synthesis - CYP450 proteins are composed of a heme group and therefore lower the intracellular heme concentration leading to activation of ALAS1
porphobilinogen
condensation of two molecules of ALA via ALA dehydratase
which two enzymes are zinc-containing and therefore are inhibited by lead
ALA dehydratase
ferrochelatase
how many ALA molecules is one heme group composed of
8
2 ALA --> porphobilinogen
4 porphobilinogen --> protoporphyrin IX
which enzyme enhances the introduction of Fe2+ to protophorphyrin creating heme
ferrochelatase
accumulation of what suggests the patient will present with abdominal pain and neuropsychiatric signs
ALA
porphobilinogen
*two molecules prior to tetrapyrrole production
accumulation of tetrapyrroles leads to what physical finding
photosensitivity - itchy and burning skin when exposed to visible sunlight
what is though to cause the photosensitivity in phorphyria
formation of superoxide radicals from oxygen
most common porphyria
porphyria cutanea tarda
defieincy in uroporphyrinogen decarboxylase leading to accumulation of uroporphyrin
what is usually associated with porphyria cutanea tarda (acute hepatic porphyria)
chronic liver disease
iron overload, alcohol, HBV or HCV
what usually precipitates acute hepatic porphyria
administration of drugs such as barbiturates and ethanol - CYP450 inducers leading to decreased concentration of heme
which enzyme is deficient in erythropoietic protoporphyria
ferrochelatase resulting in protoporphyrin IX accumulation
*the increased accumulation of Fe should decrease ALAS2
why is ALA synthase activity increased in all hepatic porphyrias
decreased production of heme, therefore ALAS1 synthesis is increased leading to over-production of ALA
treatment of porphyrias
IV injection of heme and glucose to decrease ALAS1 synthesis
green pigment seen in bruises
biliverdin
degraded component of heme before being reduced to bilirubin
two disorders associated with decreased conjugation of bilirubin in the liver
Crigler-Najjar
Gilbert syndrome
deficiency in the protein required for transport of conjugated bilirubin out of the liver
dubin-johnson-syndrome
two diseases resulting in increased conjugated bilirubin in the blood
hepatocellular jaundice
obstructive jaundice
which enzyme activity is low at birth and results in jaundice
hepatic bilirubin glucuronyltransferase
x-linked sideroblastic anemia results in deficiency of which enzyme
ALA synthase 2
coenzyme for ALA synthase
pyridoxal phosphate (PLP)
enzyme deficiency seen in acute intermittent porphyria resulting in accumulation of porphobilinogen and ALA
Hydroxymethylbilane synthase - 4 porphobiliogens --> hydroxymethylbilane
what is diagnostic of porphyria cutanea tarda
isocoproporphyrin excretion in bile and feces is diagnostic of uroporphyinogen decarboxylase deficiency
which antibiotic complexes with porphyrins and promotes their excretion
chloroquine
hydroxychloroquine
where can protoporphyrin accumulate in erythropoietic protoporphyria
1. in the bile and predispose patient to gallstone formation
2. form cystals in liver cells and decrease hepatic blood flow