Mechanistic Studies on the Reaction of Cob(I)alamin and Nitrite

Reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as nitrite (NO₂^-) are small reactive molecules present naturally in biological systems. Elevated levels of ROS and RNS (oxidative / nitrosative stress) are associated with inflammatory diseases and cancer. Vitamin B₁₂, known as cobalamin (Cbl), participates in two B₁₂-dependent enzyme reactions in mammals that are inactivated during oxidative / nitrosative stress. Cob(I)alamin (Cbl(I)), an intermediate in the B₁₂-dependent methionine synthase reaction and a biosynthetic precursor of the B₁₂ coenzymes, is readily oxidized to cob(II)alamin (Cbl(II)).The kinetics of the reaction between Cbl(I) and NO₂^- have been investigated and a reaction mechanism proposed.