Fusion of multiple enzymes to multifunctional constructs has been recognized as a viable strategy to improve enzymatic properties at various levels such as stability, activity and handling. In this study, the genes coding for cytochrome P450 BM3 from B. megaterium and formate dehydrogenase from Pseudomonas sp. were fused to enable both substrate oxidation catalyzed by P450 BM3 and continuous cofactor regeneration by formate dehydrogenase within one construct. The order of the genes in the fusion as well as the linkers that bridge the enzymes were varied. The resulting constructs were compared to individual enzymes regarding substrate conversion, stability and kinetic parameters to examine whether fusion led to any substantial improvements of enzymatic properties. Most noticeably, an activity increase of up to threefold was observed for the fusion constructs with various substrates which were partly attributed to the increased diflavin reductase activity of the P450 BM3. We suggest that P450 BM3 undergoes conformational changes upon fusion which resulted in altered properties, however, no NADPH channeling was detected for the fusion constructs.

Multi-enzyme cascades enable the production of valuable chemical compounds, and fusion of the enzymes that catalyze these reactions can improve the reaction outcome. In this work, P450 BM3 from Bacillus megaterium and an alcohol dehydrogenase from Sphingomonas yanoikuyae were fused to bifunctional constructs to enable cofactor regeneration and improve the in vitro two-step oxidation of (+)-valencene to (+)-nootkatone. An up to 1.5-fold increased activity of P450 BM3 was achieved with the fusion constructs compared to the individual enzyme. Conversion of (+)-valencene coupled to cofactor regeneration and performed in the presence of the solubilizing agent cyclodextrin resulted in up to 1080 mg L À 1 (+)-nootkatone produced by the fusion constructs as opposed to 620 mg L À 1 produced by a mixture of the separate enzymes. Thus, a two-step (+)-valencene oxidation was considerably improved through the simple method of enzyme fusion.