Uncovering the Biocatalytic Activity of the Fungal Peroxygenase of a Newly Identified Strain of Marasmius rotula

Abstract

The selective oxyfunctionalization of aliphatic C-H bonds remains a serious challenge in synthesis because of the inert nature of the bonds. Cytochrome P450s are the proteins that have evolved to be able to perform this function in nature and have been engineered to expand its substrate scope and further its potential for industrial application, but suffer from their dependence on expensive cofactors and lack of stability in extracellular contexts, limiting their effectiveness in large-scale biotechnological purposes. Fungal peroxygenases, such as that of Marasmius rotula (MroAPO), are currently being studied as promising biocatalysts for selective oxyfunctionalization of hydrocarbons because of their ability to bypass the limitations of cytochrome P450s due to their remarkable stability in extracellular contexts and its use of only H2O2 as an oxidant. Although the German strain of MroAPO (DSM 25031) has been studied since 2011, its American counterpart (ATCC 76395), which differs by seven mutations, has not been characterized to any appreciable extent. In comparing the product distribution and yields of enzymatic reactions of terminal alochols, carboxylic acids, 2-hydroxy acids, and drug molecules using ATCC 76395 by 1H NMR and GC-MS analysis to those of DSM 25031, it is clear that there are significant differences in reactivity between the two homologues. Whereas DSM 25031, for example, has been shown to be an effective catalyst for the decarboxylation of carboxylic acids, ATCC 76395 does not produce the decarboxylation product close to the yields and efficiency that are reported for its German homologue, even when 2-hydroxy acids are tested as substrates. Additionally, it shown in this thesis that photocatalytic enzymatic reactions using FMN and ATCC 76395 is possible, as proven by the efficient oxidation of ibuprofen methyl ester into hydroxy ibuprofen methyl ester which adds to the biocatalytic potential of the enzyme.