The direct hydroxylation of alkanes under mild conditions is a key issue in catalytic chemistry that addresses an increasing number of industrial and economic requirements. Cytochrome P450s are monooxygenases that are capable of oxidizing less reactive C−H bonds; however, wild-type P450s are unavailable for many important nonnative substrates such as gaseous alkanes. Here, we report the enhanced hydroxylation activities and crystallographic evidence for the role of decoy molecules in wild-type P450BM3-catalyzed hydroxylation of gaseous ethane and propane by using the next generation of decoy molecule. A cocrystal structure of P450BM3 and a decoy molecule reveals that an N-perfluoroacyl amino acid (decoy molecule) partially occupies the substrate-binding site of P450BM3. This binding of the decoy re-forms the active site pocket to allow the accommodation of small substrates and simultaneously influences the formation of compound I species by expelling water molecules from the active site.

Highly effective dipeptidic decoy molecules, which stimulate the direct hydroxylation of benzene by wild-type cytochrome P450BM3, were successfully developed through a rationally designed screening method. Extensive synthesis and step-wise screening of over 600 dipeptide derivatives were performed for the efficient evolution of decoy molecules. In the presence of N-(3-cyclopentyl)propanoyl-L-pipecolyl-L-phenylalanine (3CPPA-Pip-Phe), one of the most effective decoy molecules discovered herein, the catalytic turnover frequency and total turnover number for benzene hydroxylation reached 405 min −1 P450BM3 −1 and 54,500 P450BM3 −1 , respectively. Furthermore, the decoy molecules developed in this work drastically accelerated the hydroxylation of other non-native substrates, such as anisole and toluene, as well as nonaromatic compounds, such as cyclohexane, propane, and ethane. Using Nenanthoyl-L-pipecolyl-L-phenylalanine (C7AM-Pip-Phe), the hydroxylation rate for ethane to ethanol reached 82.7 min −1 P450BM3 −1 .

A new type of high‐pressure reactor based on liquid‐flow pressurisation using a HPLC pump has been developed. This high‐pressure reactor allows the easy and safe performance of reactions with gaseous alkanes under high‐pressures up to 10 MPa (100 atm), without the need for high‐pressure gas cylinders. The amount of substrate gas required for a single reaction is very small compared with reactions using a conventional autoclave, which, when using expensive substrate gasses, such as 13C‐labelled ethane, becomes critical. Employing this high‐pressure reactor in conjunction with cytochrome P450BM3 and the assistance of decoy molecules, the direct hydroxylation of gaseous alkanes was drastically improved. At 5 MPa the TOF of propane hydroxylation increased 10‐fold, reaching 2200 min−1. Hydroxylation of ethane was also substantially accelerated at 5 MPa, reaching a TOF of 28 min−1.

Despite CYP102A1 (P450BM3) representing one of the most extensively researchedmetalloenzymes,crystallisation of its haem domain upon modification can be ac hallenge. Crystal structures are indispensable for the efficient structurebased design of P450BM3 as ab iocatalyst. The abietane diterpenoid derivative N-abietoyl-l-tryptophan (AbiATrp) is an outstanding crystallisation accelerator for the wild-type P450BM3 haem domain, with visible crystals forming within 2hours and diffracting to an ear-atomic resolution of 1.22 . Using these crystals as seeds in across-microseeding approach, an assortment of P450BM3 haem domain crystal structures, containing previously uncrystallisable decoym olecules and diverse artificial metalloporphyrins binding various ligand molecules,a sw ell as heavily tagged haem-domain variants, could be determined. Some of the structures reported herein could be used as models of different stages of the P450BM3 catalytic cycle.

Die Kristallisation der Hämdomäne von CYP102A1 (P450BM3) kann nach Modifizierung eine Herausforderung sein. Dennoch sind solche Kristallstrukturen unentbehrlich für die wirksame strukturbezogene Entwicklung von P450BM3 als Biokatalysator. Es wurde gezeigt, dass das Abietanditerpenderivat N‐Abietoyl‐l‐tryptophan (AbiATrp) ein hervorragender Kristallisationsbeschleuniger ist. Die Nutzung von Kristallen der P450BM3‐Hämdomäne mit AbiATrp als Impfkristalle ermöglichte die rasche Mikrokristallisation bei der naszierende Kristalle innerhalb von Sekunden nach Impfung erschienen. Hierdurch wurde eine Auswahl an Kristallen der P450BM3‐Hämdomäne erhalten, die bisher nicht kristallisierbare Täuschmoleküle, diverse künstliche Metalloporphyrine, welche verschiedenartige Liganden binden, sowie zusätzlich stark getaggte Hämdomänevarianten enthalten (37 zusätzliche Aminosäuren). Manche der Strukturen könnten als Modellverbindungen verschiedener Stadien des katalytischen Zyklus von P450BM3 genutzt werden.

Biological methane oxidation is a highly desirable method for the conversion of natural gas into a liquid to meet the increasing demand for fuel and chemical feedstock as well as reducing the potent greenhouse effects of methane emissions. Because natural hemoenzymes that can catalyze the conversion of methane to methanol have not been found, it has long been considered that hemoenzymes, including cytochrome P450s (P450s), cannot catalyze the oxidative conversion of methane. Herein, we report the catalytic oxidation of methane by wild-type P450BM3, without any mutagenesis, in the presence of chemically evolved dummy substrates (decoy molecules) under high-pressure methane at 10 MPa. Our studies showed that methane was catalytically converted into methanol at room temperature with a total turnover number of 4.

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The front cover artwork for Issue 19/2019 is provided by Shoji and co‐workers at Nagoya University (Japan). The image shows the concept of their novel high‐pressure reactor which compresses gaseous alkanes by pumping liquid forcibly (the person wearing a T‐shirt) into the reaction vessel without an exit (the trunk), and pressurizes up to 10 MPa. See the Communication itself at https://doi.org/10.1002/cctc.201901323.