Interaction of Cob(III)alamins with Hypothiocyanite. Evidence for the Formation of Hypothiocyanitocobalamin

Here, we report the results of investigation of the reactions between cobalamins (Cbls) and hypothiocyanite (OSCN -), a product of thiocyanate oxidation by hydrogen peroxide in the presence of lactoperoxidase. In the case of aquacobalamin, the product, the UV-vis spectrum of which differs from the UV-vis spectra of Cbl(III)-complexes with SCN -, SO 3 2-, OCN - and CN -anions, is formed and attributed to hypothiocyanitocobalamin. This complex reacts with selenomethionine at substantially lower rate than the free OSCN -. Cyano-and methyl-Cbls are relatively stable in the presence of OSCN -. Glutathionylcobalamin is transformed to hypothiocyanitocobalamin in the presence of OSCN -excess via the oxidation of glutathionyl-ligand and subsequent binding of OSCN -by Cbl(III).