Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.14.99.3 (heme oxygenase)
 4,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heme-degrading enzymes are involved in human diseases ranging from stroke, cancer, and multiple sclerosis to infectious diseases such as malaria, diphtheria, and meningitis. All mammalian and microbial enzymes identified to date are members of the heme oxygenase superfamily and assume similar monomeric structures with an all alpha-helical fold. Here we describe the crystal structures of IsdG and IsdI, two heme-degrading enzymes from Staphylococcus aureus. The structures of both enzymes resemble the ferredoxin-like fold and form a beta-barrel at the dimer interface. Two large pockets found on the outside of the barrel contain the putative active sites. Sequence homologs of IsdG and IsdI were identified in multiple Gram-positive pathogens. Substitution of conserved IsdG amino acid residues either reduced or abolished heme degradation, suggesting a common catalytic mechanism. This mechanism of IsdG-mediated heme degradation may be similar to that of the structurally related monooxygenases, enzymes involved in the synthesis of antibiotics in Streptomyces. Our results imply the evolutionary adaptation of microbial enzymes to unique environments.
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PMID:Staphylococcus aureus IsdG and IsdI, heme-degrading enzymes with structural similarity to monooxygenases. 1552 15

Desferrioxamine inhibits cortical necrosis in neonatal rats with experimental pneumococcal meningitis, suggesting that iron-induced oxidative damage might be responsible for neuronal damage. We therefore examined the spatial and temporal profile of changes in cortical iron and iron homeostatic proteins during pneumococcal meningitis. Infection was associated with a steady and global increase of non-haem iron in the cortex, particularly in neuronal cell bodies of layer II and V, and in capillary endothelial cells. The non-haem iron increase was associated with induction of haem oxygenase (HO)-1 in neurones, microglia and capillary endothelial cells, whereas HO-2 levels remained unchanged, suggesting that the non-haem iron increase might be the result of HO-1-mediated haem degradation. Indeed, treatment with the haem oxygenase inhibitor tin protoporphyrin (which completely blocked the accumulation of bilirubin detected in HO-1-positive cells) completely prevented the infection-associated non-haem iron increase. The same cells also displayed markedly increased ferritin staining, the increase of which occurred independently of HO activity. At the same time, no increase in DNA/RNA oxidation was observed in infected animals (as assessed by in situ detection of 8-hydroxy[deoxy]guanosine), strongly suggesting that ferritin up-regulation protected the brain from iron-induced oxidative damage. Thus, although pneumococcal meningitis leads to an increase of cortical non-haem iron, protective mechanisms up-regulated in parallel prevent iron-induced oxidative damage. Cortical damage does not appear to be a direct consequence of increased iron, therefore.
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PMID:Induction of haem oxygenase-1 causes cortical non-haem iron increase in experimental pneumococcal meningitis: evidence that concomitant ferritin up-regulation prevents iron-induced oxidative damage. 1711 31