<p>Fatty acid desaturases (<db_xref db="EC" dbkey="1.14.19.1"/>) are enzymes that catalyze the insertionof a double bond at the delta position of fatty acids. There seem to be two distinct families of fatty acid desaturases which do not seem to be evolutionary related. This entry is family 2 of the desaturases andincludes, plant stearoyl-acyl-carrier-protein desaturase (<db_xref db="EC" dbkey="1.14.99.6"/>) that catalysesthe introduction of a double bond at the delta position of steraoyl-ACP to produce oleoyl-ACP [<cite idref="PUB00004734"/>] and is responsible for the conversion of saturated fatty acids to unsaturated fatty acids in the synthesis of vegetable oils, and Cyanobacteria desA [<cite idref="PUB00004074"/>] an enzyme that can introduce a second cis double bond at the delta position of fatty acid bound to membranes glycerolipids. DesA is involved in chilling tolerance; the phase transition temperature of lipids of cellular membranes being dependent on the degree of unsaturation of fatty acids of the membrane lipids.</p>