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Mechanism of S‑Adenosyl‑l‑methionine C‑Methylation by Cobalamin-dependent Radical S‑Adenosyl‑l‑methionine Methylase in 1‑Amino-2-methylcyclopropanecarboxylic Acid Biosynthesis

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journal contribution
posted on 2022-12-02, 13:41 authored by Fumitaka Kudo, Atsushi Minato, Shusuke Sato, Nayuta Nagano, Chitose Maruyama, Yoshimitsu Hamano, Junko Hashimoto, Ikuko Kozone, Kazuo Shin-ya, Tadashi Eguchi
The radical S-adenosyl-l-methionine (SAM) methylase Orf29 catalyzes the C-methylation of SAM in the biosynthesis of 1-amino-2-methylcyclopropanecarboxylic acid. Here, we determined that the methylation product is (4″R)-4″-methyl-SAM. Furthermore, we found that the 5′-deoxyadenosyl radical generated by Orf29 abstracts the pro-R hydrogen atom from the C-4″ position of SAM to generate the radical intermediate, which reacts with methylcobalamin to give (4″R)-4″-methyl-SAM. Consequently, the Orf29-catalyzed C-methylation was confirmed to proceed with retention of configuration.

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