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Comparative analysis of catalases: spectral evidence against heme‐bound water for the solution enzymes
Author(s) -
Andersson Laura A.,
Johnson Anna K.,
Simms Melissa D.,
Willingham Timothy R.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00651-o
Subject(s) - heme , chemistry , catalase , hemeprotein , ferric , ligand (biochemistry) , substrate (aquarium) , enzyme , cytochrome , stereochemistry , circular dichroism , crystallography , biochemistry , biology , inorganic chemistry , receptor , ecology
A recent X‐ray structural analysis of M. luteus catalase indicates heme‐bound H 2 O trans to the proximal tyrosinate ligand, a finding in contrast to previous X‐ray data reporting a 5‐coordinate heme for bovine liver catalase. The presence of heme‐bound H 2 O, requiring displacement prior to substrate‐binding, is likely to be catalytically significant for catalases. We have used magnetic circular dichroism (MCD) spectroscopy, a highly accurate method for assignment of heme spin‐ and coordination‐states, to study native, solution forms of bovine liver, M. luteus , and A. niger catalases. All three enzymes display similar spectral features with the weak (∼5 Δϵ m [moles·cm·Tesla] −1 intensity typical of a 5‐coordinate high‐spin ferric heme. No evidence for H 2 O‐ligation, inducing a 6‐coordinate heme, occurred upon variation of pH or buffer composition. Therefore, we suggest that the catalytically significant structure of catalases has an unoccupied heme binding site trans to the proximal tyrosinate heme ligand.