Understanding the activation mechanism of Thermomyces lanuginosus lipase using rational design and tryptophan‐induced fluorescence quenching

The attractiveness of lipases as industrial biocatalysts underlines the importance of understanding their molecular action in detail, helping future efforts to improve performance and applicability. Lipases represent a special class of carboxyl ester hydrolases, which act on long‐chained water insoluble acyl‐glycerols at the water‐lipid interface. This heterogeneous catalysis makes it very difficult to monitor the structural changes taking place in the enzyme during activation in its preferred milieu. In this review, we cover recent developments toward a deeper understanding of the interfacial activation phenomenon of lipases and discuss a selection of biophysical methods suitable for studying lipase activation. For many lipases, such as that from Thermomyces lanuginosus , a structural domain called the “lid” is directly involved in the activation process. This has been shown through alteration of the lid‐residue composition using rational design. The resulting lid‐mutants have highlighted the lid's role in governing enzymatic activity and interfacial activation. Moreover, a recently developed fluorescence‐based technique called the Tryptophan Induced Quenching method has proved to enable the direct measurement of lipase activation in water‐ethanol mixtures, and thus represents an intriguing method to gain further insight into the structural movements taking place at the water‐lipid interface. Practical applications: Lipases are important industrial biocatalysts widely used in industrial applications including detergent, leather, paper, fuel, fine chemicals, baking, cosmetics, and food. Knowledge of structural changes of lipase upon activation and identification of the amino acids involved in lipase activation is crucial for design of new variants with improved or new properties. Rational design of the lid‐region in lipases has an interesting potential for optimization of lipase function and adapting them to different environments. In order to leverage on the design of new lipase variants and their altered function, methods that enable direct measurement of lipase action directly in solution, in real time, are desired. In this context, fluorescence based methods have shown great potential and provides interesting perspectives for probing the delicate movements occurring in lipases upon activation. Interfacial activation of lipases and the lid movements studied by rational design, fluorescence quenching methods, and solvent effect – polarity driven activation.