MPST and Dravet syndrome: However, in DS, the electron transport chain is directly inhibited {as discussed later, recent data suggest that one of the reasons is that Complex IV activity is suppressed by the increased hydrogen sulfide [H2S] production, resulting from increased cystathionine-beta-synthase [CBS] and 3-mercaptopyruvate sulfurtransferase [3-MST] expression in DS cells (Panagaki et al. 2019, 2020)}.