Stannum (IV) Chloride Stimulates Vanadium (IV) Catalyzed Oxidation of NADH

Stannum has been found to be an essential ultratrace element, however, the biological functions of stannum remain to be clarified. We found that stannum (IV) chloride stimulates vanadium (IV) catalyzed free radical chain oxidation of NADH. Stannum (IV) chloride, per se, did not catalyze the NADH oxidation. Superoxide, H2O2, and OH are known to be the key species in vanadium catalyzed NADH oxidation. The inhibition of the vanadium (IV) catalyzed NADH oxidation in the presence of stannum (IV) chloride by catalase, superoxide dismutase (SOD), and hydroxyl radical scavengers indicated that the stannum (IV) chloride stimulated NADH oxidation consisted of almost the same reaction steps as that in the absence of stannum (IV) chloride. The results of inhibition studies on the NADH oxidation with SOD and catalase suggested that the reaction mixture containing stannum (IV) chloride contained a greater amount of H2O2 and a lower amount of O2 than that containing only vanadium (IV). Hydrogen peroxide is the precursor of OH in the free radical chain reaction. The stimulation of NADH oxidation by stannum (IV) chloride is due to the stimulation of H atom abstraction by OH. Stannum (IV) chloride might stimulate the generation of OH by producing H2O2.