|
| Nitric oxide | Carbon monoxide | Hydrogen sulfide |
|
| Formula | NO | CO | H2S |
| Color and odor | Colorless; a mild, sweet odor | Colorless; odorless | Colorless; smell like rotten egg |
| Free radical | Yes | No | No |
| Flammable | No | No | Yes |
| Toxicity | Yes | Yes | Yes |
| Inhibition of mitochondrial cytochrome c oxidase | Yes | Yes | Yes |
| Resources | L-arginine or nitrite | Protohaem IX | L/D-cysteine |
| Intermediate products | L-NG hydroxyarginine, citrulline | Biliverdin IX-α | Cystathionine, L-cysteine, α-ketobutyrate, and pyruvate |
| Enzymes | eNOS, iNOS, and nNOS | HO-1, HO-2, and HO-3 | CBS, CSE, 3MST/AAT, and DAO |
| Vascular effect | Vasodilation, angiogenesis | Vasodilation, angiogenesis | Vasodilation, angiogenesis |
| Inhibition inflammation | Yes | Yes | Yes |
| Antiapoptosis | Yes | Yes | Yes |
| Haem effect | Yes | Yes | Yes |
| Molecular targets | Soluble guanylate cyclase (sGC) | Soluble guanylate cyclase (sGC) | KATP (ATP-gated potassium) channel |
| Targeting outcome | Increase cGMP, activate KCa channels and nitrosylation | Increase cGMP, activate KCa channels | Increase cGMP and cAMP, activate KATP channels and sulfhydration |
| Application on human | Pulmonary hypertension, lung transplantation, and ARDS | Not available | Not available |
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