Aggregation behavior of synthetic peptide lipids with arginine in aqueous solution and construction of a vitamin B12 artificial enzyme

A novel amphiphile (N+C5Arg2C16) having an arginine residue and a dihexadecyl moiety for the double-chain segment was synthesized, and itʹs aggregate behavior was examined by electron microscopy, differential scanning calorimetry, and fluorescence polarization measurements. The hybrid vesicles formed with an alanine lipid, N+C5Ala2C16, and an arginine lipid, N+C5Arg2C16, are morphologically very stable. Hydrophobic vitamin B12 derivatives, which have carboxylic ester groups in place of the peripheral amide moieties of the naturally occurring vitamin B12, were incorporated into the single-walled vesicles of N+C5Ala2C16 and N+C5Arg2C16 to construct an artificial holoenzyme with vitamin B12 activity. In these hybrid bilayer vesicles, the enzyme mimicking reaction of methylmalonyl-CoA mutase, which is 1,2-migration of carboxylic ester group on an axial ligand of the cobalt, has been enhanced by microenvironmental effects.