Catalyzes the third of the four reactions of the long-chain fatty acids elongation cycle. This endoplasmic reticulum-bound enzymatic process, allows the addition of two carbons to the chain of long- and very long-chain fatty acids/VLCFAs per cycle. This enzyme catalyzes the dehydration of the 3-hydroxyacyl-CoA intermediate into trans-2,3-enoyl-CoA, within each cycle of fatty acid elongation. Thereby, it participates in the production of VLCFAs of different chain lengths that are involved in multiple biological processes as precursors of membrane lipids and lipid mediators. Involved in Rac1-signaling pathways leading to the modulation of gene expression. a very-long-chain (3R)-3-hydroxyacyl-CoA = a very-long-chain (2E)-enoyl-CoA + H2O (3R)-hydroxyhexadecanoyl-CoA = (2E)-hexadecenoyl-CoA + H2O Lipid metabolism; fatty acid biosynthesis. Belongs to the very long-chain fatty acids dehydratase HACD family. Shares some similarity with tyrosine phosphatase proteins but it has probably no phosphatase activity.