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The IsdG‐family of haem oxygenases degrades haem to a novel chromophore
Author(s) -
Reniere Michelle L.,
Ukpabi Georgia N.,
Harry S. Reese,
Stec Donald F.,
Krull Robert,
Wright David W.,
Bachmann Brian O.,
Murphy Michael E.,
Skaar Eric P.
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2010.07076.x
Subject(s) - biliverdin , oxygenase , heme , biochemistry , heme oxygenase , porphyrin , enzyme , biology , chromophore , dioxygenase , oxidoreductase , biliverdin reductase , stereochemistry , chemistry , photochemistry
Summary Enzymatic haem catabolism by haem oxygenases is conserved from bacteria to humans and proceeds through a common mechanism leading to the formation of iron, carbon monoxide and biliverdin. The first members of a novel class of haem oxygenases were recently identified in Staphylococcus aureus (IsdG and IsdI) and were termed the IsdG‐family of haem oxygenases. Enzymes of the IsdG‐family form tertiary structures distinct from those of the canonical haem oxygenase family, suggesting that IsdG‐family members degrade haem via a unique reaction mechanism. Herein we report that the IsdG‐family of haem oxygenases degrade haem to the oxo‐bilirubin chromophore staphylobilin. We also present the crystal structure of haem‐bound IsdI in which haem ruffling and constrained binding of oxygen is consistent with cleavage of the porphyrin ring at the β‐ or δ‐ meso carbons. Combined, these data establish that the IsdG‐family of haem oxygenases degrades haem to a novel chromophore distinct from biliverdin.