The enzyme leukotriene-C₄ synthase (EC 4.4.1.20) catalyzes the reaction

leukotriene C₄ ${\displaystyle \rightleftharpoons }$ leukotriene A₄ + glutathione

This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is leukotriene-C₄ glutathione-lyase (leukotriene-A₄-forming). Other names in common use include leukotriene C₄ synthetase, LTC4 synthase, LTC4 synthetase, leukotriene A₄:glutathione S-leukotrienyltransferase, (7E,9E,11Z,14Z)-(5S,6R)-5,6-epoxyicosa-7,9,11,14-tetraenoate:glutathione leukotriene-transferase, (epoxide-ring-opening), (7E,9E,11Z,14Z)-(5S,6R)-6-(glutathion-S-yl)-5-hydroxyicosa-7,9,11,14-tetraenoate glutathione-lyase (epoxide-forming). This enzyme participates in arachidonic acid metabolism.

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 2PNO, 2UUH, and 2UUI.