Abstract
Tuberculosis, the deadliest human lung disease caused by Mycobacterium tuberculosis, continues to be a global health threat, and finding new drugs and drug targets seems an ongoing battle. The cytochrome P450 CYP125A1 enzyme of M. tuberculosis H37Rv, which is involved in cholesterol metabolism, is a well-established target for drug development. Research is ongoing to identify new compounds that target this enzyme. Understanding the structure-activity relationship of CYP125 family members is crucial for developing a specific and efficient inhibitor. In this direction, this study analyzed 21 crystal structures of CYP125 family enzymes, unraveling the factors responsible for substrate specificity and the amino acids that play a key role in catalysis. One of the unique features of CYP125A1 is its active site cavity shape, which determines the specificity of substrates and inhibitors. The active site cavity is shaped like a letter box, lined by hydrophobic residues, and it transitions into a funnel-like shape with a progressive narrowing as it approaches the heme. Due to this shape, the cholesterol and cholest-4-en-3-one serve as substrates, but not androstenedione, as the former molecules have an alkyl side chain that extends down the narrow funnel channels, interacting with the heme iron. Different binding patterns were observed for substrates and indole-derived inhibitors. Both type I and type II interactions were observed with the non-azole P450 inhibitor LP10 and indole-derived compounds, where the side chain of the indole-derived compound determined the type of interaction. This study provides a comprehensive understanding of the structure-function analysis of P450 enzymes and the interactions of CYP125A members with various ligands. Our findings pave the way for designing new and specific CYP125A1 inhibitors that will ultimately be developed into novel anti-TB drugs.