[3P-1] Poster 3 (3P-01ー3P-47)

[3P-27] Structure-based evolutionary study of methylenetetrahydrofolate reductase (MTHFR) from Sphingobium sp. SYK-6

^○Hongyang Yu^1,2, Naoyuki Kuwabara¹, Naofumi Kamimura³, Ryo Kato³, Miki Senda¹, Eiji Masai³, Toshiya Senda^1,2 (1.SBRC, KEK, 2.SOKENDAI, 3.Nagaoka University of Technology)

Evolutionary adaptations of enzymes are frequently observed under extreme environments but rarely reverse the enzyme reactivity. MethyleneH4folate reductase (MTHFR) has been considered to catalyze the reduction of CH2-THF to methylH4folate (CH3-THF) in cells. However, MTHFR from Sphingobium sp. SYK-6 (S6MTHFR), which can utilize small molecular weight lignin such as vanillate as a sole carbon source, seems to catalyze the reverse reaction. In S. SYK-6, CH3-THF is generated by demethylation of vanillate, and the resultant CH3-THF is converted into CH2-THF by S6MTHFR for the 1C metabolism. To understand the molecular mechanism of the unique catalytic reaction of S6MTHFR, we biochemically and structurally analyzed S6MTHFR. As expected, S6MTHFR only catalyzes the oxidation of CH3-THF. Structure-based mutational analysis revealed that L48, F215, C219, and F269 form a specific binding site of CH3-THF. Conversely, NADH, which serves as a hydride donor in the typical MTHFR, is hampered accessing the active site by L48 and P49. Interestingly, the above-described residues are conserved among S6MTHFR homologs, suggesting that these homologs form a new class in the MTHFR family with the reverse catalytic reaction.