The trypsin-like serine-type endopeptidase TYSND1 cleaves HSD17B4 (Peroxisomal multifunctional enzyme type 2, MFP-2) between amino acid residues 311 and 312, yielding HSD17B4(1-311) and HSD17B4(312-736) (Okumoto et al. 2011, also inferred from mouse homologs). HSD17B4(1-311) dehydrogenates 3-hydroxyacyl-CoA; HSD17B4(312-736) acts as an enoyl-CoA hydratase (Jiang et al. 1997, reviewed in Huyghe et al. 2006). (In vitro, HSD17B4(312-736) facilitates the transfer of 7-dehydrocholesterol and phosphatidylcholine between membranes.) The uncleaved protein (HSD17B4) also catalyzes these reactions.