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Research article

J. Microbiol. Biotechnol. 2010; 20(9): 1359-1366

Published online September 28, 2010 https://doi.org/10.4014/jmb.1005.05012

Copyright © The Korean Society for Microbiology and Biotechnology.

Characterization of an O-methyltransferase from Streptomyces avermitilis MA-4680

Youngdae Yoon 1, Younghee Park 1, Youngshim Lee 1, Yong sub Yi 1, Geunhyeong Jo 1, Jun cheol Park 2, Joong-hoon Ahn 1 and Yoongho Lim 1*

1Division of Bioscience and Biotechnology, BMIC, RCD, Konkuk University, Seoul 143-701, Korea, 2National Institute of Animal Science, Rural Development Administration, Suwon 441-706, Korea

Received: May 10, 2010; Accepted: June 1, 2010

Abstract

A search of the Streptomyces avermitilis genome reveals
that its closest homologs are several O-methyltransferases.
Among them, one gene (viz., saomt5) was cloned into the
pET-15b expression vector by polymerase chain reaction
using sequence-specific oligonucleotide primers. Biochemical
characterization with the recombinant protein showed
that SaOMT5 was S-adenosyl-L-methionine-dependent Omethyltransferase.
Several compounds were tested as
substrates of SaOMT5. As a result, SaOMT5 catalyzed Omethylation
of flavonoids such as 6,7-dihydroxyflavone,
2',3'-dihydroxyflavone, 3',4'-dihydroxyflavone, quercetin,
and 7,8-dihydroxyflavone, and phenolic compounds such
as caffeic acid and caffeoyl Co-A. These reaction products
were analyzed by TLC, HPLC, LC/MS, and NMR
spectroscopy. In addition, SaOMT5 could convert phenolic
compounds containing ortho-dihydroxy groups into Omethylated
compounds, and 6,7-dihydroxyflavone was
known to be the best substrate. SaOMT5 converted 6,7-
dihydroxyflavone into 6-hydroxy-7-methoxyflavone and
7-hydroxy-6-methoxyflavone, and caffeic acid into ferulic
acid and isoferulic acid, respectively. Moreover, SaOMT5
turned out to be a Mg2+-dependent OMT, and the effect of
Mg2+ ion on its activity was five times greater than those of
Ca2+, Fe2+, and Cu2+ ions, EDTA, and metal-free medium.

Keywords: O-Methyltransferase, Streptomyces avermitilis, flavonoids