Structure-guided manipulation of the regioselectivity of the cyclosporine A hydroxylase CYP-sb21 from Sebekia benihana .
Li, F., Ma, L., Zhang, X., Chen, J., Qi, F., Huang, Y., Qu, Z., Yao, L., Zhang, W., Kim, E.S., Li, S.(2020) Synth Syst Biotechnol 5: 236-243
- PubMed: 32775708 
- DOI: https://doi.org/10.1016/j.synbio.2020.07.004
- Primary Citation of Related Structures:  
6M4S - PubMed Abstract: 
The cytochrome P450 enzyme CYP-sb21 from the rare actinomycete Sebekia benihana is capable of hydroxylating the immunosuppressive drug molecule cyclosporine A (CsA) primarily at the 4th N-methyl leucine (MeLeu 4 ), giving rise to γ -hydroxy- N -methyl-l-Leu 4 -CsA (CsA-4-OH). This oxidative modification of CsA leads to dramatically reduced immunosuppressive activity while retaining the hair growth-promoting side-effect, thus demonstrating great application potential in both pharmaceutical and cosmetic industries. However, this P450 enzyme also hydroxylates CsA at the unwanted position of the 9th N -methyl leucine (MeLeu 9 ), indicating that the regioselectivity needs to be improved for the development of CsA-4-OH into a commercial hair growth stimulator. Herein, we report the crystal structure of CYP-sb21 in its substrate-free form at 1.85 Å. Together with sequence and 3D structure comparisons, Autodock-based substrate docking, molecular dynamics (MD) simulation, and site-directed mutagenesis, we identified a number of key residues including R294, E264, and M179 that can improve catalytic efficiency or change the regioselectivity of CYP-sb21 towards CsA, setting the stage for better enzymatic preparation of CsA-4-OH. This study also provides new insights into the substrate recognition and binding mechanism of P450 enzymes that accommodate bulky substrates.
Organizational Affiliation: 
State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong, 266237, China.