Heme Metabolism Flashcards
Cyclic compounds formed by the linkage of 4 pyrrole rings through methyne or methenyl bridges
PORPHYRINS
IRON PORPHYRINS - Heme of Hemoglobin
MAGNESIUM CONTAINING PORPHYRIN -
CHLOROPHYLL
3 important porphyrins
UROPORPHYRIN
COPROPORPHYRIN
PROTOPORPHYRIN
Iron in the heme is in
FERROUS STATE
TRANSPORT of Oxygen in Blood
HEMOGLOBIN
STORAGE of Oxygen in Blood
MYOGLOBIN
Involvement in ETC
Cytochrome C
Hydroxylation of xenobiotics
Cytochrome P450
Degradation of hydrogen peroxide
CATALASE
Oxidation of Tryptophan
TRYPTOPHAN PYRROLASE
Site of Heme Synthesis
all tissues EXCEPT mature erythrocytes
cytoplasm and mitochondria
Substrates of Heme Synthesis
Succinyl CoA and Glycine
Rare limiting step of Heme Synthesis
glycine + succinyl CoA –> delta aminolevulinic acid (ALA)
ALA SYNTHASE
Pyridoxine - cofactor
Isoform of ALAS expressed throughout the BODY
ALAS I
rate limiting step
HEME - (-) regulator if ALAS I
induced by drugs whose metabolism requires cytochromes
Isoform of ALAS expressed in erythrocyte precursor cells
ALAS II
not feedback regulated by heme
not induced by drugs
Formation of Porphobilinogen
ALA DEHYDRATASE - condenses 2 molecules of ALA
(-) by heavy metal ions that replace the zinc
cytosol
The first porphyrin precursor formed
UROPORPHYRINOGEN
Enzyme most sensitive to lead poisoning
ALA DEHYDRATASE
LEAD POISONING
lead inactivates many enzymes in heme synthesis
INCREASED urinary ALA and free erythrocyte porphyrins
microcytic, hypochromic ANEMIA
headache, memory loss
peripheral NEUROPATHY, claw hand, wrist drop
nausea, abdominal pain, diarrhea
lead lines in gums
lead deposits EPIPHYSES
The final step in heme synthesis
Formation of Heme by Incorporation of Iron
FERROCHELATASE (HEME SYNTHASE)
MITOCHONDRIA
Group of disorders d.t. abnormalities in the pathway of biosynthesis of heme
Porphyrias
photosensitivity
neuropsychiatric symptoms
abdominal pain
MC porphyria
Prophyria Cutanea Tarda (PCT)
photosensitivity
urine that is red to brown in natural light d.t. uroporphyrins
MC acute porphyria
Acute Intermittent Porphyria
abdominal pain
neuropsychiatric symptoms d.t. ALA and PBG accumulation
MC porphyria in children
Erythropoietic Protoporphyria (EPP)
Porphyria that is frequently seen in countries where Hepa C and HIV is prevalent
Pophyria Cutanea Tarda
