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. a very-long-chain (3R)-3-hydroxyacyl-CoA = a very-long-chain (2E)-enoyl-CoA + H2O (3R)-hydroxyhexadecanoyl-CoA = (2E)-hexadecenoyl-CoA + H2O (3R)-hydroxyoctadecanoyl-CoA = (2E)-octadecenoyl-CoA + H2O (3R)-hydroxyeicosanoyl-CoA = (2E)-eicosenoyl-CoA + H2O (3R)-hydroxydocosanoyl-CoA = (2E)-docosenoyl-CoA + H2O (3R)-hydroxytetracosanoyl-CoA = (2E)-tetracosenoyl-CoA + H2O (3R)-hydroxyhexacosanoyl-CoA = (2E)-hexacosenoyl-CoA + H2O Lipid metabolism; fatty acid biosynthesis. May interact with enzymes of the ELO family (including ELOVL1); with those enzymes that mediate condensation, the first of the four steps of the reaction cycle responsible for fatty acids elongation, may be part of a larger fatty acids elongase complex. Expressed in heart. N-glycosylated. 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.