Natural products, a chemically and structurally diverse class of molecules, possess a wide spectrum of biological activities, have been used therapeutically for millennia, and have provided many lead compounds for the development of synthetic drugs. Cytochrome P450 enzymes (P450s, CYP) are widespread in nature and are involved in the biosynthesis of many natural products. P450s are heme-containing enzymes that use molecular oxygen and the hydride donor NAD(P)H (coupled via enzymic redox partners) to catalyze the insertion of oxygen into C-H bonds in a regio- and stereo-selective manner, effecting hydroxylation and several other reactions. With the rapid development of systems biology, numerous novel P450s have been identified for the biosynthesis of natural products, but there are still several challenges to the efficient heterologous expression of active P450s. This review covers recent developments in P450 research and development, including the properties and functions of P450s, discovery and mining of novel P450s, modification and screening of P450 mutants, improved heterologous expression of P450s in microbial hosts, efficient whole-cell transformation with P450s, and current applications of P450s for the biosynthesis of natural products. This resource provides a solid foundation for the application of highly active and stable P450s in microbial cell factories to biosynthesize natural products.

Microbial synthesis of valuable hemoproteins has become a popular research topic, and Pichia pastoris is a versatile platform for the industrial production of recombinant proteins. However, the inadequate supply of heme limits the synthesis of high‐active hemoproteins. Here a strategy for enhancing intracellular heme biosynthesis to improve the titers and functional activities of hemoproteins is reported. After selecting a suitable expressional strategy for globins, the efficient heme‐supply P. pastoris chassis is established by removing the spatial segregation during heme biosynthesis, optimizing precursor synthesis, assembling rate‐limiting enzymes using protein scaffolds, and inhibiting heme degradation. This robust chassis produces several highly active hemoproteins, including porcine myoglobin, soy hemoglobin, Vitreoscilla hemoglobin, and P450‐BM3, which can be used in the development of artificial meat, high‐cell‐density fermentation, and whole‐cell catalytic synthesis of high‐value‐added compounds. Furthermore, the engineered chassis strain has great potential for producing and applying other hemoproteins with high activities in various fields.

By exploiting versatile P450 enzymes, whole‐cell biocatalysis can be performed to synthesize valuable compounds in Escherichia coli. However, the insufficient supply of heme limits the whole‐cell P450 biocatalytic activity. Here a strategy for improving intracellular heme biosynthesis to enhance the catalytic efficiencies of P450s is reported. After comparing the effects of improving heme transport and biosynthesis on P450 activities, intracellular heme biosynthesis is optimized through the integrated expression of necessary synthetic genes at proper ratios and the assembly of rate‐limiting enzymes using DNA‐guided scaffolds. The intracellular heme level is fine‐tuned by the combined use of mutated heme‐sensitive biosensors and small regulatory RNA systems. The catalytic efficiencies of three different P450s, BM3, sca‐2, and CYP105D7, are enhanced through fine‐tuning heme biosynthesis for the synthesis of hydroquinone, pravastatin, and 7,3′,4′‐trihydroxyisoflavone as example products of chemical intermediate, drug, and natural product, respectively. This strategy of fine‐tuned heme biosynthesis will be generally useful for developing whole‐cell biocatalysts involving hemoproteins.