Elucidation of the structure of methanopterin, a coenzyme from Methanobacterium thermoautotrophicum, using two‐dimensional nuclear‐magnetic‐resonance techniques

Abstract

Methanopterin is a coenzyme involved in methanogenesis. From 2 kg wet cells of Methanobacterium thermoautotrophicum about 35 μmol methanopterin were isolated. The structure of this compound was elucidated by various two‐dimensional nuclear‐magnetic‐resonance techniques. Methanopterin was identified as N‐[1′‐(2″‐amino‐4″‐hydroxy‐7″‐ methyl‐6″‐ pteridinyl)ethyl]‐4‐[2′,3′,4′,5′‐ tetrahydroxypent‐1′‐ yl (5′→1″) O‐α‐ribofuranosyl‐5″‐phosphoric acid] aniline, in which the phosphate group is esterified with α‐hydroxyglutaric acid. The molecular formula of the sodium salt of methanopterin at pH 7.0 is C₃₀H₃₈O₁₆N₆PNa₃·xH₂O (x is about 4). The anhydrous sodium salt of methanopterin has a molecular mass of 838.60 Da and the molar absorption coefficient at 342 nm is 7.4 mM⁻¹ cm⁻¹ at pH 7.0.