Interaction of Hydrogen Sulfide with Nitric Oxide in the Cardiovascular System

Figure 1

Biosynthesis of NO and H₂S. NO is synthesized by three different isoforms of NOS, namely, nNOS, eNOS, and iNOS. These isoforms are almost identical in structure and functions. A functional NOS is made up of two identical monomers, each with four cosubstrates (NADPH, FAD, FMN, and BH₄). L-Arginine is oxidized into L-citrulline along with the production of NO. H₂S is produced by the catalytic action of 3 different enzymes, CBS, CSE, and 3-MST. Each enzyme is expressed in organ-specific manner and catalyses the production of H₂S by oxidizing L-homocysteine and L-cysteine. Pyruvate, α-ketobutyrate and serine are produced as bi-products. The interaction between these two gases can give rise to production of few intermediate products (e.g., S-nitrosothiols). As explained in this review article later, nitroxyl (HNO), thionitrous acid (HSNO), and other possible unknown compounds have been shown to induce some interesting effect in cardiovascular system.