[1S05e] 13. Microbial Engineering for Natural Products Synthesis - Part 3

5:00 PM - 5:15 PM JST(8:00 AM - 8:15 AM UTC)

[1MENP-14] Biosynthetic Studies of 5-Azacytidine Containing 1,3,5-Triazine Moiety

○Takeshi Tsunoda¹, Akari Umezawa¹, Yu Nakashima², Chitose Maruyama³, Yoshimitsu Hamano³, Yasuhide Inokuma¹, Masanobu Uchiyama⁴, Yasushi Ogasawara¹, Hiroyuki Morita², Tohru Dairi¹ (1. Hokkaido Univ. (Japan), 2. Toyama Univ. (Japan), 3. Fukui Pref. Univ. (Japan), 4. The Univ. of Tokyo (Japan))

Keywords:

biosynthesis,nucleoside natural products

5-Azacytidine (1) is a cytidine-mimic nucleoside with 5-azacytosine (2) as a base, which possesses a unique triazine structure by replacing C atom at 5-positiono with N atom of cytosine. 1 was isolated as a natural product more than 60 years ago and is currently used for the treatment of myelodysplastic syndrome. In this study, we identified 1 biosynthetic gene cluster by a bioinformatic approach and revealed that 2 was biosynthesized from guanosine triphosphate (GTP) by three enzymes, AzcE, AzcA, and AzcB/C. AzcE is a GTP cyclohydrolase and catalyzed the conversion of GTP to 2,5,6-triaminopyrimidin-4(3H)-one (3). Then, 3 was converted to the triazine structure, 6-amino-4-oxo-4,5-dihydro-1,3,5-triazine-2-carboxylic acid (4), by a unique enzyme, AzcA. Finally, AzcB/C catalyzed thiamine pyrophosphate-dependent decarboxylation of 4 to yield 2. Because all the enzymes catalyzed unprecedent reactions, we solved crystal structures of AzcA and AzcB/C. The structure of AzcE was also analyzed by cryo-electro microscopy. Taking biochemical analysis together, we figured out the reaction mechanisms of each of the enzymes.