Epoxide hydrolases catalyze the conversion of epoxides to corresponding diols. The catalytic triad nucleophile is an invariable aspartate that opens the epoxide ring by nuclophile attack. The mammalian soluble EHs contain 2 evolutionarily distinct domains, the N-terminal domain is similar to bacterial haloacid dehalogenase (not related to alpha/beta-hydrolase fold), while the C-terminal domain is similar to soluble plant EH, microsomal EH, and bacterial haloalkane_dehalogenase (HLD). In InterPro IPR000639 groups Epoxide hydrolase and Haloalkane dehalogenase. IPR000639; Epoxide hydrolase contains some Carboxymethylbutenolide_lactonase (trembl Q9WWZ4) Carbon-carbon_bond_hydrolase (trembl Q98I15 Q9KH20 Q9K5C1 Q9KWQ6 Q9ZAY1 Q9ZNJ3 Q9RBF3 Q9RBT0) Monoglyceridelipase_lysophospholip (trembl Q97TG8). In ESTHER they are classified in the later sub family. (there are also epoxide hydrolases not related to a/b hydrolases ex: 1NWW limonene-1,2-epoxide hydrolase Arand et al. 2003) Zhu et al. (2003) identified compound heterozygosity for 2 mutations in the EPHX1 gene, which resulted in a significant decrease in EPHX1 promoter activity.