Porphyrins Flashcards
Chemical structure of heme (# of pyrrole rings and the valence of iron)
Tetrapyrole ring (4 rings) with alpha/beta chains and iron with a 2+ valence
Two anatomical sites in the body where porphyrins are synthesized
Marrow or long bones and liver
Enzyme deficiency for the most common porphyria
-porphyria cutanea tarda
uroporphyrinogen decarboxylase
Enzyme deficiency/ inhibition in lead toxicity
Gamma-Aminolevulinic acid dehydratase
Enzyme deficiency in Acute Intermittent Porphyria
Porphobilinogen deaminase
Enzyme deficiency resulting in Congenital Erythropoietic Porphyria
Uroporphyringogen III cosynthase
Enzyme deficiency resulting in Erythropoietic Protoporphyria; the enzyme necessary for the incorporation of iron in protoporphyrin IX
Ferrochelatase
these are unstable, colorless, and non-fluorescent
porphyrinogens (reduced porphyrins)
these are stable, colored (dark red or purple), and fluorescent (excite at 420nm; emission at 620nm)
Porphyrins
reagent used in the porphyrin screening test
Erlich’s Reagent
Best method for quantitative porphyrin assays
Liquid Chromatography (LC) or LC/MS
Three most common porphyrias
Acute intermittent porphyria, porphyria cutanea tarda, and erythropoietic porphyria/protoporphyria
one typical symptom of acute intermittent porphyria
acute abdominal pain
Exacerbating factors of acute intermittent porphyria
drugs/alcohol, fasting/dieting, oral contraceptives
porphyrin that is increased in acute intermittent porphyria
increased porphobilinogen (PBG)
what happens as a urine sample from a patient with acute intermittent porphyria is left at room temp for at least 2 hours
urine gets darker red/port wine color as it sets
FOur typical symptoms of porphyria cutanea tarda
fragile skin, blisters, scarring, hyperpigmentation
Porphyrin that is increased in porphyria cutanea tarda
Urinary uroporphyrinogen III
Two symptoms of erythropoietic protoporphyria
painful skin with skin swelling (congenital or aquired)
Four physical characteristics and typical color of urine of a ptient with congenital erythropoietic porphyria
Extreme photosensitivity, reddish/brown teeth staining, mental retardation, abnormal growth patterns; urine is pink/red
Two enzymes in the heme biosynthetic pathway that are inhibited in lead poisoning
ALA dehydrase and ferrochelatase
What is typically analyzed in the lab to difinitively diagnose lead poisoning?
Increased urinary 5-ALA and coproporphyrin, Increased RBC zinc protoporphyrin, and increased lead in whole blood
