Cytochrome P450: A Vital Biosynthetic Enzymes for Drug Metabolism

Overview of Cytochrome P450

Cytochrome P450 (CYP450), is a family of hemoglobin-coupled monooxygenases. In mammals, CYP450 oxidizes steroids, fatty acids, and xenobiotics, playing an important role in the metabolism of various compounds as well as in the synthesis and breakdown of hormones. In plants, they regulate the synthesis of defense compounds, fatty acids, and hormones. With the progress of research, the effects of CYP450 on organic synthesis and drug metabolism have been gradually explored.

Fig 1. The secondary and tertiary structure of P450 protein

CYP enzymes can be classified according to the membrane-bound and soluble forms. In prokaryotes, CYP450 is a soluble protein. In eukaryotes, they are usually bound to the endoplasmic reticulum or inner mitochondrial membranes. CYP450 can also be classified into four classes based on electron transfer processes, depending on how electrons from NAD(P)H are delivered to the catalytic site. Class I proteins require FAD-containing reductase and iron thioredox. Class II proteins require only the FAD/FMN containing P450 reductase to transfer electrons. Class III enzymes are self-sufficient and do not require electron donors, whereas Class IV CYP450 receives electrons directly from NAD(P)H.

CYP450 and Biosynthesis

CYP450 involved in drug metabolism mainly includes seven important subtypes of CYP1, CYP2, and CPY3 families, especially CPY3A4. CYP3 family accounts for 28.8% of the total intrahepatic CYP450, which is an important enzyme involved in the first-pass effect of oral drugs. Many opioid analgesics can be metabolized by CYP3A4, and drug-drug interaction (DDI) mediated by P-GP and CYP3A4 often occurs when combined with antiretroviral drugs. Due to the widespread distribution of CYP450 and its important role in metabolism in vivo, more than 90% of clinical DDI is caused by the alteration of CYP450 activity. Predicting metabolic models in the early stage of drug discovery is of great significance to improve the success rate of drug discovery. Therefore, the study of CYP enzyme metabolism matters a lot for new drug development.

In addition, CYP450 is one of the most versatile biocatalysts in nature, which not only catalyzes multiple reaction types but also has an extremely broad substrate spectrum. Its diverse functionality has great potential for synthetic biology applications.

CYP450 catalyzes the synthesis of natural products such as terpenoids, sterols, and alkaloids, and is widely used in the industry. In addition, the engineering development of CYP, the research and development of biosensors, the mining of the properties of novel CYP, and the continuous development of new enzymes provide the direction for the further application of CYP.

Fig 2. Taxol biosynthesis

In 2019, a research group of the Chinese Academy of Sciences published the first study on the heterologous synthesis of taxadiene-5α-ol, a key intermediate of paclitaxel, in plant chassis in Nature Communications. Researchers modified the chloroplast localization of paclitaxene-5α-hydroxylase and CYP450 reductase. The spatial consistency of the GGPP-TS-T5H/CPR metabolic pathway was ensured, and the synthesis of 5α-hydroxytaxdiene was successfully achieved.

Biosynthesis of natural products usually requires that CYP450 and P450 reductase are physically close enough to perform electron transfer reactions. However, the functional expression of eukaryotic P450 in bacteria is often tricky. In August 2022, Nature Catalysis reported on an electronic channel strategy based on the application of Photorhabdus luminescens CipB scaffolding protein, which implements efficient electron transfer by bringing P450 and reductase close together. Recombinant E. coli strains were successfully developed to synthesize lutein, (+)-nootkatone, apigenin, and L-3, 4-dihydroxyphenylalanine (L-DOPA).

Summary

In conclusion, CYP450 has been extensively studied since its discovery was reported in 1962 in the journal JBC, including structural features, catalytic mechanisms, regulation, and many other aspects of biochemistry. Scientists believe that further research and engineering advances on CYP450 will bring great benefits to synthetic biology in the future.

References

1. Danièle Werck-Reichhart and René Feyereisen, Cytochromes P450: a success story, Genome Biology, 2000, 1, reviews3003.1.
2. Guengerich FP. Cytochrome P450 research and The Journal of Biological Chemistry. J Biol Chem. 2019 Feb 1;294(5):1671-1680.
3. Li, J., Mutanda, et al. Chloroplastic metabolic engineering coupled with isoprenoid pool enhancement for committed taxanes biosynthesis in Nicotiana benthamiana. Nat Commun., 2019, 10, 4850.