55-140 Lecture Notes - Phosphoribosyl Pyrophosphate, Biliverdin, Chlorophyll

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Published on 1 Feb 2013
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PORPHRYIN METABOLISM
distribution
- heme proteins (hemoglobin, cytochrome)
- related proteins (corrin ring, chlorophyll)
RDS in heme biosynthesis: succinyl CoA + glycine ALA
explains glycine’s long lifespan in vivo
ALAS regulation – tln blocked by IBP
Iron present IBP bound tln can occur
similar strategy for ferritin tln
**loss of IBP binding can also destabilize transcripts (transferrin)**
regulation:
hemin inhibits heme biosynthesis
activates globin translation
degradation:
RBC destruction releases lots of heme
heme biliverdin, bilirubin (yellow)
LIVER: bilirubin bilirupin diglucuoronide excreted in bile
CLINICAL PROBLEMS
ACUTE INTERMITTENT PORPHYRIA:
most common
PBG deaminase activity deficient + ALAS activated excess PBA/ALA
neuropathy, psychosis, abdominal pain
PORPHYRIA CUTANEA TARDA
uroporhyrinogen decarboxylase deficiency
extreme photosensitivity (blistering), hyperpigmentation, facial hair
ERYTHROPOETIC PROTOPORPHYRIA
deficiency of ferrochelatase
photosensitivity, hepatobiliary dysfunction, anemia
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JAUNDICE – hyper bilirubinemia
neonatal – increased destruction of fetal RBC’s
UV light treatment
hepatocellular – reduced bilirubin conjugation cannot excrete in bile
obstructive – conjugated bilirubin cannot be excreted due to obstruction
(pancreatic carcinoma)
(gall stones)
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