<p> Fatty acid desaturases are enzymes that catalyze the insertion of a double bond at the delta position of fatty acids.</p> <p>There seem to be two distinct families of fatty acid desaturases which do not seem to be evolutionary related.</p> <p>Family 1 is composed of:</p><ul> <li> - Stearoyl-CoA desaturase (SCD) (<db_xref db="EC" dbkey="1.14.19.1"/>) [<cite idref="PUB00002505"/>]. </li></ul><p> Family 2 is composed of:</p><ul><li> - Bacterial fatty acid desaturases.</li><li> - Plant stearoyl-acyl-carrier-protein desaturase (<db_xref db="EC" dbkey="1.14.19.1"/>) [<cite idref="PUB00004734"/>], this enzyme catalyzes the introduction of a double bond at the delta(9) position of steraoyl-ACP to produce oleoyl-ACP. This enzyme is responsible for the conversion of saturated fatty acids to unsaturated fatty acids in the synthesis of vegetable oils.</li><li> - Cyanobacterial DesA [<cite idref="PUB00004074"/>], an enzyme that can introduce a second cis double bond at the delta(12) 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.</li></ul><p>This entry contains fatty acid desaturases belonging to Family 2. </p>