Functional characterization and unraveling the structural determinants of novel steroid hydroxylase CYP154C7 from Streptomyces sp. PAMC26508

This study characterized cytochrome P450 enzyme CYP154C7 from <i>Streptomyces</i> sp. PAMC26508, emphasizing its capability to hydroxylate steroids, especially at the 16α-position. The enzymatic assay of CYP154C7 demonstrated effective conversion across a pH range of 7.2-7.6, with optimal activity at 30 °C in the Pdx/PdR plus NADH system. Kinetic analysis on most converted steroids (androstenedione and adrenosterone) was performed which shows a greater affinity for androstenedione (<i>K</i> _<i>m</i> , 11.06 ± 1.903 μM; <i>V</i> _max, 0.0062 ± 0.0002 sec^-1) compared to adrenosterone (<i>K</i> _<i>m</i> , 34.50 ± 6.2 μM; <i>V</i> _max, 0.0119 ± 0.0007 sec^-1). A whole-cell system in <i>Escherichia coli</i>, overexpressing recombinant CYP154C7, achieved substantial conversion for steroids, indicating that CYP154C7 can also be used as a potential whole-cell biocatalyst. To gain structural insights, homology models of CYP154C7 and its homologs were constructed using CYP154C5 (PDB ID: 6TO2), refined, validated, and used for docking studies. Comparative docking analysis suggests that lysine (K236) in the active site and tyrosine (Y197) in the substrate access channel of CYP154C7 are crucial for substrate selectivity and catalytic efficiency. This study suggests that CYP154C7 could be a promising candidate for developing modified steroids, providing valuable insights for protein engineering to design commercially useful CYP steroid hydroxylases with diverse substrate specificities.