In enzymology, an O-phosphoserine sulfhydrylase () is an enzyme that catalyzes the chemical reaction O-phospho-L-serine + hydrogen sulfide L-cysteine + phosphate Thus, the two substrates of this enzyme are O-phospho-L-serine and hydrogen sulfide, whereas its two products are L-cysteine and phosphate. This enzyme belongs to the family of transferases, specifically those transferring aryl or alkyl groups other than methyl groups. The systematic name of this enzyme class is O-phospho-L-serine:hydrogen-sulfide 2-amino-2-carboxyethyltransferase. This enzyme is also called O-phosphoserine(thiol)-lyase. This enzyme participates in cysteine metabolism and sulfur metabolism. References EC 2.5.1 Enzymes of unknown structure