italic>O-
methyltransferases (OMTs) are one of the key tailoring
enzymes in the
biosynthesis of many
natural products, O-
methylation can not only reduce the reactivity of
natural products, but also alter their
solubility, stability and
biological activities. Based on the
transcriptome data of
Ardisia japonica, a full-length
cDNA sequence of candidate OMT (termed as AjOMT1) was cloned by
reverse transcription-
polymerase chain reaction (RT-PCR) and expressed in
Escherichia coli (E. coli) for the first
time.
In vitro enzyme catalytic activity assay showed that the recombinant AjOMT1 could effectively catalyze
quercetin to form O-methylated products. Most importantly, AjOMT1 showed unprecedented substrate promiscuity towards structurally various compounds including
flavonoids,
stilbenes,
coumarins,
alkaloids and phenylpropanoids, especially preferring to the compounds with adjacent phenolic hydroxyl groups, and showed regio-selectivity. These results suggested that AjOMT1 could be used as the tool
enzyme to conduct O-
methylation of different types of compounds to produce diverse active methylated products, and provide a new
method for
drug discovery, even universal part for
synthetic biology of
natural products.