Enzymes are proteins with biocatalytic properties. Our research on enzymes concerns CoA dependent, lipid metabolising enzymes (2E-enoyl-CoA hydratases, 3S-hydroxyacyl-CoA dehydrogenases and thiolases) as well as prolyl 4-hydroxylases (human collagen prolyl 4-hydroxylases). These projects are multidisciplinary projects using a wide range of techniques, including protein crystallography, cryoEM, biophysical characterisation, enzymology, as well as biocomputing techniques. These projects are aimed at better understanding of the reaction mechanisms of these interesting enzymes. The studies on 2E-enoyl-CoA hydratase are also aimed at changing its substrate specificity in order to use its biocatalytic power for the synthesis of high value compounds that are difficult to synthesize other wise. The studies on human collagen prolyl 4-hydroxylase are first of all aimed at understanding its processivity properties. This knowledge will also be used for discovering inhibitors that might be of use in developing therapeutics concerning diseases related to high collagen prolyl 4-hydroxylase activity, such as cancer and fibrosis.