Porphyrins Flashcards
Two anatomical sites in the body where porphyrins are synthesized
- Marrow of long bones
- Liver
Chemical structure of heme (# f pyrrole rings and the valence of iron)
Tetrapyrole ring (4 rings) w/ alpha/beta chains and iron w/ a 2+ valence
What is the most common porphyria?
Porphyria cutanea tarda
Enzyme deficiency in porphyria cutanea tarda
Uroporphyrinogen decarboxylase
Enzyme deficiency in acute intermittent porphyria
Porphobilinogen (PBG) deaminase
Enzyme deficiency in congenital erythropoietic porphyria
Uroporphyrinogen III cosynthase
Enzym deficiency resulting in erythropoietic protoporphyria; the enzyme necessary for the incorporation of iron in protoporphyrin X
Ferrochelatase
Porphyrinogens (reduced porphyrins)
- Relative stability
- Color
- Fluorescent properties
- Relative stability: unstable
- Color: colorless
- Fluorescent properties: non-fluorescent
Porphyrins
- Relative stability
- Color
- Fluorescent properties
- Relative stability: stable
- Color: colored (dark red or purple)
- Fluorescent properties: fluorescent (excite at 420nm; emission at 620nm)
What is the reagent used in the porphyrin screening test?
Ehrlich’s reagent
What is the best method for quantitative porphyrin assays?
Liquid Chromatography (LC) or LC/MS
3 most common porphyrias
- Acute intermittent porphyria
- Porphyria cutanea tarda
- Erythropoietic porphyria/protoporphyria
Acute intermittent porphyria
- 1 typical symptom
Acute abdominal pain
Acute intermittent porphyria
- Exacerbating factors
- Drugs/alcohol
- Fasting/dieting
- Oral contraceptives
Acute intermittent porphyria
- Porphyrin that is increased
Porphobilinogen (PBG)
Acute intermittent porphyria
- What happens as a urine sample from a patient is left at room temperature for at least 2 hours?
Urine gets darker (red/port wine color) as it sets
What is the nickname for porphyria cutanea tarda?
“Vampire’s Disease”
Porphyria cutanea tarda
- 4 typical symptoms
- Fragile skin
- Blisters
- Scarring
- Hyperpigmentation
Porphyria cutanea tarda
- Porphyrin that is increased
Urinary uroporphyrinogen III
Erythropoietic protoporphyria
- 2 symptoms
- Painful skin
- Skin swelling (congenital or acquired)
4 physical characteristics of a patient w/ congenital erythropoietic porphyria
- Extreme photosensitivity
- Reddish/brown teeth staining
- Mental retardation
- Abnormal growth patterns
Color of urine in a patient w/ congenital erythropoietic porphyria
Urine is pink/red
Two enzymes in the heme biosynthetic pathway that are inhibited in lead poisoning
- ALA dehydrogenase
- Ferrochelatase
What is typically analyzed in the lab to definitively diagnose lead poisoning?
- Increased urinary delta-ALA and coproporphyrin
- Increased RBC zinc protoporphyrin
- Increasedlead in whole blood
