text: << Hydrogen sulfide >> (H(2)S), a regulatory gaseous molecule that is endogenously synthesized by [[ cystathionine gamma-lyase ]] (CSE) and/or cystathionine beta-synthase (CBS) from L-cysteine (L-Cys) metabolism, is a putative vasodilator, and its role in nitric oxide (NO) production is unexplored.