Homology Modeling and Molecular Dynamics Simulation Combined with X-ray Solution Scattering Defining Protein Structures of Thromboxane and Prostacyclin Synthases

Structural insights into understudied human cytochrome P450 enzymes

Human cytochrome P450 (CYP) enzymes are widely known for their pivotal role in the metabolism of drugs and other xenobiotics as well as of endogenous chemicals. In addition, CYPs are involved in numerous pathophysiological pathways and, hence, are therapeutically relevant. Remarkably, a portion of promising CYP targets is still understudied and, as a consequence, untargeted, despite their huge therapeutic potential. An increasing number of X-ray and cryo-electron microscopy (EM) structures for CYPs have recently provided new insights into the structural basis of CYP function and potential ligand binding. This structural knowledge of CYP functionality is essential for both understanding metabolism and exploiting understudied CYPs as drug targets. In this review, we summarize and highlight structural knowledge about this enzyme class, with a focus on understudied CYPs and resulting opportunities for structure-based drug design. Teaser: This review summarizes recent structural insights into understudied cytochrome P450 enzymes. We highlight the impact of molecular modeling for mechanistically explaining pathophysiological effects establishing understudied CYPs as promising drug targets.

Futile cycling by human microsomal cytochrome P450 enzymes within intact fission yeast cells

Human cytochrome P450 enzymes (CYPs or P450s) are known to be reduced by their electron transfer partners in the absence of substrate and in turn to reduce other acceptor molecules such as molecular oxygen, thereby creating superoxide anions (O₂^-•). This process is known as futile cycling. Using our previously established fission yeast expression system we have monitored cells expressing each one of the 50 human microsomal CYPs in the absence of substrate for oxidation of dihydroethidium in living cells by flow cytometry. It was found that 38 of these display a statistically significant increase in O₂^-• production. More specifically, cells expressing some CYPs were found to be intermediate strength O₂^-• producers, which means that their effect was comparable to that of treatment with 3 mM H₂O₂. Cells expressing other CYPs had an even stronger effect, with those expressing CYP2B6, CYP5A1, CYP2A13, CYP51A1, or CYP1A2, respectively, being the strongest producers of O₂^-•.

Impact of peripheral mutations on the access channels of human cytochrome P450 1A2

Communicated by Ramaswamy H. Sarma.