Peroxidase Activity of Myoglobin Variants Reconstituted with Artificial Cofactors.

Abstract

Myoglobin (Mb) can react with hydrogen peroxide (H2O2) to form a highly active intermediate compound and catalyse oxidation reactions. To enhance this activity, known as pseudo‐peroxidase activity, previous studies have focused on the modification of key amino acid residues of Mb or the heme cofactor. In this work, the Mb scaffold (apo‐Mb) was systematically reconstituted with a set of cofactors based on six metal ions and two ligands. These Mb variants were fully characterised by UV‐Vis spectroscopy, circular dichroism (CD) spectroscopy, inductively coupled plasma mass spectrometry (ICP‐MS) and native mass spectrometry (nMS). The steady‐state kinetics of guaiacol oxidation and 2,4,6‐trichlorophenol (TCP) dehalogenation catalysed by Mb variants were determined. Mb variants with iron chlorin e6 (Fe−Ce6) and manganese chlorin e6 (Mn−Ce6) cofactors were found to have improved catalytic efficiency for both guaiacol and TCP substrates in comparison with wild‐type Mb, i. e. Fe‐protoporphyrin IX‐Mb. Furthermore, the selected cofactors were incorporated into the scaffold of a Mb mutant, swMb H64D. Enhanced peroxidase activity for both substrates were found via the reconstitution of Fe−Ce6 into the mutant scaffold.