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. May be an anti-phosphatase that prevents CDKA-1 dephosphorylation and activation. Involved in the hormonal control of cell division and differentiation. Required for proliferation control of meristematic and non-meristematic cells. Negative regulator of the cell cycle. a very-long-chain (3R)-3-hydroxyacyl-CoA = a very-long-chain (2E)-enoyl-CoA + H2O Lipid metabolism; fatty acid biosynthesis. Interacts with CDKA-1; but only with the 'Tyr-15' phosphorylated protein. Interacts with PAS1. Part of the fatty acid elongase complex which contains a beta-ketoacyl-CoA synthase (KCS), a beta-ketoacyl-CoA reductase (KCR), a beta-hydroxyacyl-CoA dehydratase (HCD) and an enoyl-CoA reductase (ECR) (Probable). Found in the cytoplasm of dividing cells but moves into the nucleus upon cell differentiation. High expression in young seedlings, roots, root tips, flowers and young siliques. Lower levels in leaves and stems. Embryo lethal when homozygote. Plants with reduced expression of PAS2 show impaired embryo and seedling development associated with cell de-differentiation and proliferation. Root growth is reduced, due to a delay in cell plate establishment during cytokinesis (PubMed:21896643). 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 since the potential active site Cys residue in position 65 is replaced by Gly.