Structure-Guided Manipulation of the Regioselectivity of the Cyclosporine A Hydroxylase CYP-sb21 from Sebekia Benihana

The study investigated the enzyme CYP-sb21 from Sebekia benihana, which hydroxylates cyclosporine A (CsA), producing a derivative with reduced immunosuppressive activity but retaining hair growth-promoting effects. The enzyme's preference for hydroxylating at the 4th N-methyl leucine (MeLeu4) of CsA was noted, but its unwanted hydroxylation at MeLeu9 prompted research to improve regioselectivity. The crystal structure of CYP-sb21 was solved at 1.85 Å resolution, and molecular dynamics simulations, docking, and site-directed mutagenesis were used to identify key residues for enhancing catalytic efficiency and altering regioselectivity. Mutants with improved hydroxylating activity and catalytic efficiency were created, offering insights into substrate recognition and binding mechanisms of P450 enzymes and potential enzymatic production of CSA-4-OH for hair growth stimulation.