Aldehyde Dehydrogenase 1 in the Metabolism and Bioactivation of Organic Nitrates

Le résumé fourni par la source

The role of the cysteine residues, at position 302 and 303, of Aldehyde Dehydrogenase 1 (ALDH1) in the metabolism and activation of organic nitrates (ORN) was examined by selective mutation of these amino acids to alanine. C303A was devoid of dehydrogenase activity against acetaldehyde, while the C302A mutant exhibited slightly increased activity vs. the wild type, WT, (1.83 ± 0.61 vs 0.984 ± 0.115 U/mg, p<0.01). Cumulative nitric oxide (NO) generation was monitored via a NO electrode and NTG denitration was assessed via LCMS. ALDH1 C303A did not metabolize NTG significantly and failed to produce measurable NO. In comparison, C302A metabolism of NTG to its 1,2‐dinitrate metabolite was significantly slower than WT (p<0.05). NO production by C302A was decreased vs. WT with two model ORN, viz., isosorbide‐5‐mononitrate (5‐ISMN, 36.8 ± 6.6 % vs. WT, p<0.001) and NTG (45.1 ± 5.1 % vs. WT, p<0.01). Pre‐incubation with 0.1mM NTG, but not 1mM 5‐ISMN, for 10min significantly reduced WT ALDH1 dehydrogenase activity (7.07 ± 1.54 % vs control, p<0.001). C302A showed a similar pattern of dehydrogenase inhibition. ALDH1 C302A maintained the ability to metabolize 5‐ISMN which however is a poor substrate for ALDH2. These data suggest that C303 of ALDH1 is critical to its dehydrogenase, denitrating and NO generating activities against ORN while C302 participates to modulate these activities. (Supported in part by NIH grant HL81580)

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