A stable bacterial peroxidase with novel halogenating activity and an autocatalytically linked heme prosthetic group

Reconstructing the phylogenetic relationships of the main evolutionary lines of the mammalian peroxidases lactoperoxidase (LPO) and myelo-peroxidase (MPO) revealed the presence of new bacterial heme peroxidase subfamilies. Here, for the first time, an ancestral bacterial heme peroxidase is shown to catalyse (besides conventional peroxidase activity) bromide and chloride oxidation more efficiently than LPO and MPO. The recombinant protein allowed monitoring of the autocatalytic peroxide-driven formation of covalent heme to protein bonds. Thereby the high-spin ferric rhombic heme spectrum became similar to LPO, the standard reduction potential of the Fe(III)/Fe(II) couple shifted to more positive values (-145 ± 10 mV at pH 7) and the conformational and thermal stability of the protein increased. We discuss structure-function relationships of this new peroxidase in relation to its mammalian counterparts and ask for its putative physiological role.