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).