Synthetic Co(III) complexes containing an N5 donor sets like that of cobalamin (Cbl) undergo glutathionylation, to generate biomimetic species of glutathionylcobalamin (GSCbl), an important form of Cbl found in nature. For this study, a new Co(III) complex derived from the polypyridyl pentadentate N5 ligand N4PyCO2Me was   synthesized. The compound [Co(N4PyCO2Me)Cl]Cl2 (1  ) was characterized by X-ray crystallography, UV-vis, IR, 1H-NMR, and 13C-NMR spectroscopies and mass spectrometry. Reaction of 1  with glutathione (GSH) generates the biomimetic species [Co(N4PyCO2Me)(SG)]2+ (2  ), which was generated in situ and characterized by HRMS, UV-vis and 1H-NMR spectroscopies. 1H-NMR and UV-vis spectroscopic data are consistent with ligation of the cysteine thiolate of GSH to the Co(III) center of 2  , as occurs in GSCbl. Reaction of the Co(III) complex [Co(Bn-CDPy3)Cl]Cl2 (3  ) with GSH generates glutathionylated species [Co(Bn-CDPy3)(SG)]2+ (4  ), analogous to 2  . Kinetic analysis indicated that glutathionylation occurs via a second order process, at a slower rate with 1  and 3  than with aquocobalamin. Observed equilibrium constants were also smaller for 2  and 4  versus GSCbl.

Glutathionylation of cobalamin model complexes

243rd National Meeting (2012)

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