Reaction of Nitroxyl, an Aldehyde Dehydrogenase Inhibitor, with N-Acetyl-L-Cysteine

Abstract 

Nitroxyl (HNO) is the aldehyde dehydrogenase (AlDH) inhibitor produced by catalase action on cyanamide. Incubation of N-acetyl-L-cysteine (NAC), a reagent with a free sulfhydryl group, with Piloty's acid (a nitroxyl generator) suggested that NAC was acting as a competitive “trap” for nitroxyl. Elucidation of the structure of this reaction product should give an insight as to how nitroxyl interacts with AlDH, a sulfhydryl enzyme. We now present evidence that the product formed is N-acetyl-L-cysteinesulfinamide (NACS). We have synthesized NACS and showed that this synthetic product was identical to the product formed in the trapping experiment. Both had identical RT values by reverse phase HPLC and identical RF values by TLC using three different solvent systems. The structural identification of this nitroxyl trapped product as a sulfinamide now allows the chemical confirmation of the active-site cysteine residue of AlDH as Cys-302. Published by Elsevier Science Inc.

Keywords:  Aldehyde dehydrogenase, Nitroxyl, Sulfhydryl inhibition, N-Acetyl-L-cysteine, Piloty's acid, Cyanamide, Alcohol deterrent