Expanding the Toolbox for Biocatalytic Halogenation by Identification and Characterization of Three Vanadium Chloroperoxidases.

Halogenation reactions are essential for producing many fine and bulk chemicals. Vanadium-dependent chloroperoxidases (VCPOs) are promising biocatalysts for a more sustainable production of halogenated products because they are cofactor independent, use hydrogen peroxide (H2O2) as oxygen donor, tolerate high H2O2 concentrations, and catalyze all halogenations except fluorination. Despite their outstanding catalytic potential, few VCPOs have been identified yet, and detailed information on their catalytic characteristics is lacking. Here, we report the heterologous expression of three previously uncharacterized VCPOs in Escherichia coli and their validation. One of the enzymes was identified in the fungus Curvularia clavata (CcVCPO). The other two were found in the bacteria Crocinitomix catalasitica (CrocVCPO) and in an uncultivated Bacteroidetes strain (UbVCPO) isolated from a water sample taken from lake Neuchâtel in Switzerland. These enzymes exhibit highly attractive features, including thermostability up to 40°C for the bromination reaction of monochlorodimedone (MCD), the highest chlorination turnover numbers reported to date for wild-type VCPOs for the variant UbVCPO, as well as increased enzyme activation at 40°C and in the presence of methanol or ethanol for the same enzyme variant. These findings significantly expand the VCPO toolbox and highlight their potential for sustainable halogenation processes.