The activity of human CYP2D6 in low water organic solvents

Lyophilization conditions for the storage of monooxygenases

Cyclohexanone monooxygenase (CHMO) was used as a model enzyme to find suitable freeze-drying conditions for long-term storage of an isolated monooxygenase. CHMO is a Baeyer-Villiger monooxygenase (BVMO) known for its ability to catalyze a large number of oxidation reactions. With a focus on establishing the optimal formulation, additives were tested for enzyme stabilization during and after lyophilization. The results were successfully transferred to two other monooxygenases, namely the BVMO cyclopentadecanone monooxygenase (CPDMO) and a cytochrome P450 monooxygenase, P450 BM3. In the absence of a lyoprotectant, lyophilized P450 BM3 is almost completely inactivated, while the lyophilized BVMOs quickly lost activity when stored at 50°C. Lyophilization in the presence of 2% (w/v) sucrose was found to be the best formulation to preserve activity and protect against inactivation when stored as lyophilizate at 50°C.

Directed evolution of cytochrome P450 enzymes for biocatalysis: exploiting the catalytic versatility of enzymes with relaxed substrate specificity

Cytochrome P450 enzymes are renowned for their ability to insert oxygen into an enormous variety of compounds with a high degree of chemo- and regio-selectivity under mild conditions. This property has been exploited in Nature for an enormous variety of physiological functions, and representatives of this ancient enzyme family have been identified in all kingdoms of life. The catalytic versatility of P450s makes them well suited for repurposing for the synthesis of fine chemicals such as drugs. Although these enzymes have not evolved in Nature to perform the reactions required for modern chemical industries, many P450s show relaxed substrate specificity and exhibit some degree of activity towards non-natural substrates of relevance to applications such as drug development. Directed evolution and other protein engineering methods can be used to improve upon this low level of activity and convert these promiscuous generalist enzymes into specialists capable of mediating reactions of interest with exquisite regio- and stereo-selectivity. Although there are some notable successes in exploiting P450s from natural sources in metabolic engineering, and P450s have been proven repeatedly to be excellent material for engineering, there are few examples to date of practical application of engineered P450s. The purpose of the present review is to illustrate the progress that has been made in altering properties of P450s such as substrate range, cofactor preference and stability, and outline some of the remaining challenges that must be overcome for industrial application of these powerful biocatalysts.