Aminomethanesulfonic Acid Participates in Reduction of Nitrate to Nitrite in the Presence of Diethyldithiocarbamate and Peroxidase

In order to explore the possibility of producing undesirable compounds by aminomethanesulfonic acid (AMSA) added to biological systems, we investigated nitrate reduction in a reaction mixture containing potassium nitrate, sodium diethyldithiocarbamate (DEDTC), AMSA, and horseradish peroxidase. In this mixture, nitrate was reduced to nitrite. Nitrate-reducing activity was enhanced, with a pH increase from 6.8 to 9.8, and then it dropped sharply. The maximum nitrate-reducing activity in our experimental condition was 1.83 ìmol mg protein –1 min –1 . The reduction of nitrate was inhibited by the addition of superoxide ion scavengers such as nitro blue tetrazolium, epinephrine, ascorbic acid, and cytochrome c , and limited by slow dissociation of AMSA to sulfite that immediately participated in nitrate reduction reaction. The results suggest that application of AMSA to the biological systems containing nitrate, DEDTC, and peroxidase (or superoxide ion) may lead to undesirable production of nitrite due to nitrate reduction.