A Novel O - and S -Methyltransferase from Pleurotus sapidus Is Involved in Flavor Formation.

Increasing consumer aversion to non-natural flavoring substances is prompting a heightened interest in enzymatic processes for flavor production. This includes methylation reactions, which are often performed by using hazardous chemicals. By correlation of aroma profile data and transcriptomic analysis, a novel O -methyltransferase (OMT) catalyzing a respective reaction within the formation of p -anisaldehyde was identified in the mushroom Pleurotus sapidus . Heterologous expression in E. coli followed by purification allowed for further characterization of the enzyme. Besides p -hydroxybenzaldehyde, the proposed precursor of p -anisaldehyde, the enzyme catalyzed the methylation of further hydroxylated aromatic compounds at the meta - and para -position. The K m values determined for p -hydroxybenzaldehyde and S -adenosyl-l-methionine were 80 and 107 μM, respectively. Surprisingly, the studied enzyme enabled the transmethylation of thiol-nucleophiles, as indicated by the formation of 2-methyl-3-(methylthio)furan from 2-methyl-3-furanthiol. Moreover, the enzyme was crystallized at a resolution of 2.0 Å, representing the first published crystal structure of a basidiomycetous OMT.