Involved in cholesterol side chain degradation (PubMed:22045806, PubMed:25203216). Catalyzes the hydration of 3-oxo-4,17-pregnadiene-20-carboxyl-CoA (3-OPDC-CoA) to form 17-hydroxy-3-oxo-4-pregnene-20-carboxyl-CoA (17-HOPC-CoA), in the modified beta-oxidation pathway for cholesterol side chain degradation (PubMed:25203216, PubMed:31568719). Can also use octenoyl-CoA and decenoyl-CoA, with lower efficiency (PubMed:25203216). 3-oxochola-4,17-dien-22-oyl-CoA + H2O = 17-hydroxy-3-oxochol-4-en-22-oyl-CoA (2E)-octenoyl-CoA + H2O = 3-hydroxyoctanoyl-CoA (2E)-decenoyl-CoA + H2O = 3-hydroxydecanoyl-CoA In the absence of the Ltp2 aldolase, ChsH1/ChsH2 can hydrate only about 30% of the 3-OPDC-CoA substrate. Complete turnover requires the presence of Ltp2. Steroid metabolism; cholesterol degradation. Heterodimer composed of ChsH1 and ChsH2. Two heterodimers combine to form an heterotetramer (PubMed:25203216). The complex interacts with Ltp2 via the DUF35 C-terminal region of ChsH2 (PubMed:29109182, PubMed:31568719). The ChsH1-ChsH2-Ltp2 protein complex is composed of two protomers that form a heterohexameric structure through the Ltp2 dimerization interface (PubMed:31568719). The DUF35 C-terminal region is not required for hydratase activity (PubMed:25203216). This region is involved in interaction with LtpA and is required for optimal LtpA aldolase activity (PubMed:29109182). Belongs to the thioester dehydratase family.