Reaction of nitroxyl, an aldehyde dehydrogenase inhibitor, with N-acetyI-L-cysteine

Nitroxyl (HNO) is the aldehyde dehydrogenase (AIDH) inhibitor produced by c atalase action on cyanamide. Incubation of N-acetyl-L-cysteine (NAC), a rea gent with a free sulfhydryl group, with Piloty's acid (a nitroxyl generator ) suggested that NAC was acting as a competitive "trap" for nitroxyl. Eluci dation of the structure of this reaction product should give an insight as to how nitroxyl interacts with ALDH, a sulfhydryl enzyme. We now present ev idence that the product formed is N-acetyl-L-cysteinesulfinamide (NACS). We have synthesized NAGS and showed that this synthetic product was identical to the product formed in the trapping experiment. Both had identical RT va lues by reverse phase HPLC and identical RF values by TLC using three diffe rent solvent systems. The structural identification of this nitroxyl trappe d product as a sulfinamide now allows the chemical confirmation of the acti ve-site cysteine residue of AIDH as Cys-302. Published by Elsevier Science Inc.