The 4S pathway involves four main enzymes: DszA, DszB, DszC, and DszD. These enzymes work sequentially to convert dibenzothiophene (DBT), a common sulfur compound in fossil fuels, into 2-hydroxybiphenyl (HBP) and sulfite, which can be further oxidized to sulfate. This process specifically targets the sulfur atom, leaving the carbon skeleton intact, thus preserving the fuel's calorific value.
