Formylglutathione hydrolase(Esterase D) is a member of the esterase D family. Esterase D is a serine hydrolase involved in the detoxification of formaldehyde. Esterase D is active toward various substrates including O-acetylated sialic acids, and it may possibly be involved in the recycling of sialic acids. Esterase D is used as a genetic marker for retinoblastoma and Wilson’s disease.