Necessary for the introduction of cis unsaturation into fatty acids. Catalyzes the dehydration of (3R)-3-hydroxydecanoyl-ACP to E-(2)-decenoyl-ACP and then its isomerization to Z-(3)-decenoyl-ACP. Can catalyze the dehydratase reaction for beta-hydroxyacyl-ACPs with saturated chain lengths up to 16:0, being most active on intermediate chain length (By similarity). a (3R)-hydroxyacyl-[ACP] = a (2E)-enoyl-[ACP] + H2O (3R)-hydroxydecanoyl-[ACP] = (2E)-decenoyl-[ACP] + H2O (2E)-decenoyl-[ACP] = (3Z)-decenoyl-[ACP] Lipid metabolism; fatty acid biosynthesis. Homodimer. Belongs to the thioester dehydratase family. FabA subfamily.