Purification and characterization of glutathione-independent denitration enzyme of organic nitrate esters in rabbit hepatic cytosol.

The enzyme responsible for glutathione (GSH)-independent denitration of organic nitrate esters was purified by gel chromatography, ion-exchange chromatography and affinity chromatography from rabbit hepatic cytosol. The enzyme showed a molecular mass of 175 kDa and consisted of three subunits of 59 kDa. The enzyme exerted its maximum activities at around pH 9, when isosorbide dinitrate (ISDN) was used as substrate. The enzyme possessed a low Km value (10(-6) M) for various organic nitrate esters. The present enzyme is likely to be involved in the denitration of organic nitrate esters in conjunction with known enzymes, GSH S-transferase (GST) and cytochrome P450.