Reduction of organic nitrates catalysed by xanthine oxidoreductase under anaerobic conditions

Xanthine oxidoreductase catalyses the anaerobic reduction of glyceryl trini trate (GTN), isosorbide dinitrate and isosorbide mononitrate to inorganic n itrite using xanthine or NADH as reducing substrates. Reduction rates are m uch faster with xanthine as reducing substrate than with NADH. In the prese nce of xanthine, urate is produced in essentially 1:1 stoichiometric ratio with inorganic nitrite. further reduction of which is relatively slow. Orga nic nitrates were shown to interact with the FAD sire of the enzyme. In the course of reduction of GTN, xanthine oxidoreductase was progressively inac tivated by conversion to its desulpho form. It is proposed that xanthine ox idoreductase is one of several flavoenzymes that catalyse the conversion of organic nitrate to inorganic nitrite in vivo. Evidence for its further inv olvement in reduction of the resulting nitrite to nitric oxide is discussed . (C) 2001 Elsevier Science B.V. All rights reserved.