Enzymes play an indispensable role in our everyday life. They are not only catalysing a vast number of reactions in our body, they are incorporated into many industrial processes. In the light of pollution and decline of fossil resources it is essential to develop new production routes to pharmaceutical and chemical target compounds. The exaggerated use of antibiotics and the resulting increase of multi‐resistant bacteria is another threat of our century. Solving this problem requires deep understanding of antibiotic resistance mechanisms to enable rational drug‐design. The main focus of the thesis lies on terpene synthases, which catalyse the cyclisation of linear isoprenoid precursors to complex macrocycles. These compounds are high commercial targets of the chemical and pharmaceutical industry. Terpenes constitute the largest group of natural compounds. Especially in the class of the diterpenes many compounds possess antibacterial, anti‐viral, insecticidal and antiinflammatory properties. White biotechnology opens up new routes for the production of terpenes in bacteria in a sustainable manner. In order to optimise terpene titers in bacteria, structural knowledge of the involved terpene synthases is crucial. Here, we report the crystal structures of the diterpene synthases CotB2 and IES in complex with various substrate‐analogues. Furthermore, the structure of the oleate hydratase OhyRe was elucidated. Products of this enzyme are used as surfactants and lubricants in industry. The X‐ray crystal structures of biotechnologically relevant enzymes obtained during this thesis contribute to illustrate their reaction mechanisms and binding modes. As another part of this thesis, the structure of AlbAS, a bacterial antibiotic‐binding protein, was solved. The protein structure sheds light on the binding mechanism of the antibacterial drug albicidin at a molecular level.
