Aggregation behavior of synthetic peptide lipids with arginine in aqueous solution and construction of a vitamin B-12 artificial enzyme

A novel amphiphile (N(+)C(5)Arg2C(16)) having an arginine residue and a dih exadecyl moiety for the double-chain segment was synthesized, and it's aggr egate behavior was examined by electron microscopy, differential scanning c alorimetry, and fluorescence polarization measurements. The hybrid vesicles formed with an alanine lipid, N+- C(5)Ala2C(16), and an arginine lipid, N( +)C(5)Arg2C(16), are morphologically very stable. Hydrophobic vitamin B-12 derivatives, which have carboxylic ester groups in place of the peripheral amide moieties of the naturally occurring vitamin B-12, were incorporated i nto the single-walled vesicles of N(+)C(5)Ala2C(16) and N(+)C(5)Arg2C(16) t o construct an artificial holoenzyme with vitamin B-12 activity. In these h ybrid 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. (C) 2000 E lsevier Science B.V. All rights reserved.