Catalyzes the third of the very long-chain fatty acids (VLCFA) elongation four-step cycle (condensation, reduction, dehydration, and reduction). This endoplasmic reticulum-elongation process is characterized by the addition of two carbons to the lipid chain through each cycle. This enzyme catalyzes the dehydration of the 3-hydroxyacyl-CoA intermediate into trans-2,3-enoyl-CoA, within each cycle of elongation. Therefore, it participates in the production of various VLCFAs 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 (PubMed:18554506). Interacts with BCAP31 (PubMed:15024066). Highly expressed in testis, spleen, prostate, colon and heart, followed by moderate expression in thymus, ovary, small intestine, peripheral blood leukocytes, liver, skeletal muscle and pancreas. Weakly detected in kidney, placenta, brain and lung. Turns over rapidly through degradation by the proteasome system. 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.