New Cofactor‐Independent Hydration Biocatalysts: Structural, Biochemical, and Biocatalytic Characteristics of Carotenoid and Oleate Hydratases

In industrial biocatalytic processes the class of lyases (EC 4) is underrepresented and only a few enzymes are used in industrial scale reactions. Hydro‐lyases (EC 4.2.1) catalyze the non‐hydrolytic and non‐oxidative addition of water to a CC bond. Without a biocatalyst, this reaction proceeds under strong acidic conditions with no enantioselectivity. From a chemical point of view carotenoid 1,2‐hydratase (CrtC) performs a very challenging addition of water to an isolated CC bond. This hydration reaction proceeds without assistance of electron withdrawing groups or transition metals, which makes it very interesting from both an industrial, as well as enzymatic point of view. Oleate hydratase (OHase) catalyzes the enantioselective conversion of oleic acid into 10‐hydroxystearic acid. The crystal structure of OHase from Lactobacillus acidophilus was published recently, which contributes to the understanding of this enzyme. These enzymes could broaden the organic chemist’s toolbox.