Synthesis, solution and crystal structure of the coenzyme B12 analogue Coβ-2′-fluoro-2′,5′-dideoxyadenosylcobalamin

•Synthesis of Coβ-2′-fluoro-2′,5′-dideoxyadenosylcobalamin, lacking the critical 2′-OH group•Solution structure of 2′FAdoCbl has similar features as that of coenzyme B12 (AdoCbl).•Crystal structure of 2′FAdoCbl is similar to the structure of AdoCbl in the crystal.•First coenzyme B12 analogue with 19F-label in the organometallic moiety for 19F NMR

Crystal structure analyses have helped to decipher the mode of binding of coenzyme B12 (AdoCbl) in the active site of AdoCbl-dependent enzymes. However, the question of how such enzymes perform their radical reactions is still incompletely answered. A pioneering study by Gruber and Kratky of AdoCbl-dependent glutamate mutase (GLM) laid out a path for the movement of the catalytically active 5′-deoxyadenosyl radical, in which H-bonds between the protein and the 2′- and 3′-OH groups of the protein bound AdoCbl would play a decisive role. Studies with correspondingly modified coenzyme B12-analogues are of interest to gain insights into cofactor binding and enzyme mechanism. Here we report the preparation of Coβ-2′-fluoro-2′,5′-dideoxyadenosylcobalamin (2′FAdoCbl), which lacks the 2′-OH group critical for the interaction in enzymes. 2′FAdoCbl was prepared by alkylation of cob(I)alamin, obtained from the electrochemical reduction of aquocobalamin. Spectroscopic data and a single crystal X-ray analysis of 2′FAdoCbl established its structure, which was very similar to that one of coenzyme B12. 2′FAdoCbl is a 19F NMR active mimic of coenzyme B12 that may help to gain insights into binding interactions of coenzyme B12 with AdoCbl-dependent enzymes, proteins of B12 transport and of AdoCbl-biosynthesis, as well as with B12-riboswitches.

Graphical abstractA coenzyme B12 mimic carrying a 19F-label is presented and suggested useful for studies with B12-dependent enzymes.Figure optionsDownload full-size imageDownload as PowerPoint slide