title: Computational identification and binding analysis of orphan human cytochrome P450 4X1 enzyme with substrates.
abstract: BACKGROUND
  Cytochrome P450s (CYPs) are important heme-containing proteins, well known for their monooxygenase reaction. The human cytochrome P450 4X1 (CYP4X1) is categorized as "orphan" CYP because of its unknown function. In recent studies it is found that this enzyme is expressed in neurovascular functions of the brain. Also, various studies have found the expression and activity of orphan human cytochrome P450 4X1 in cancer. It is found to be a potential drug target for cancer therapy. However, three-dimensional structure, the active site topology and substrate specificity of CYP4X1 remain unclear.
  
  
  METHODS
  In the present study, the three-dimensional structure of orphan human cytochrome P450 4X1 was generated by homology modeling using Modeller 9v8. The generated structure was accessed for geometrical errors and energy stability using PROCHECK, VERFIY 3D and PROSA. A molecular docking analysis was carried out against substrates arachidonic acid and anandamide and the docked substrates were predicted for drug-likeness, ADME-Tox parameters and biological spectrum activity.
  
  
  RESULTS
  The three-dimensional model of orphan human cytochrome P450 4X1 was generated and assessed with various structural validation programmes. Docking of orphan human cytochrome P450 4X1 with arachidonic acid revealed that TYR 112, ALA 126, ILE 222, ILE 223, THR 312, LEU 315, ALA 316, ASP 319, THR 320, PHE 491 and ILE 492 residues were actively participating in the interaction, while docking of CYP4X1 with anandamide showed that TYR 112, GLN 114, PRO 118, ALA 126, ILE 222, ILE 223, SER 251, LEU 315, ALA 316 and PHE 491 key residues were involved in strong interaction.
  
  
  CONCLUSIONS
  From this study, several key residues were identified to be responsible for the binding of arachidonic acid and anandamide with orphan human cytochrome P450 4X1. Both substrates obeyed Lipinski rule of five in drug-likeness test and biological spectrum prediction showed anticarcinogenic activity. Compared to anandamide, arachidonic acid showed strong interaction with cytochrome P450 4X1 and also less health effect in certain human system in ADME-Tox prediction. These findings provide useful information on the biological role and structure-based drug design of orphan human cytochrome P450 4X1.
authors.affiliation: Centre for Bioinformatics Research, Institute of Systems Biology (INBIOSIS), University Kebangsaan Malaysia, 43600, UKM Bangi, Selangor, Malaysia. sureshkumar@ukm.edu.my.
authors.forename: Suresh
authors.initials: S
authors.lastname: Kumar
mesh_terms: D000595:Amino Acid Sequence; D016718:Arachidonic Acid / Q000378:metabolism; D001095:Arachidonic Acids / Q000378:metabolism; D001665:Binding Sites; D019295:Computational Biology / Q000379:methods*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism*; D063388:Endocannabinoids / Q000378:metabolism; D006801:Humans; D008024:Ligands; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D053284:Polyunsaturated Alkamides / Q000378:metabolism; D011485:Protein Binding; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D040681:Structural Homology, Protein; D013379:Substrate Specificity
chemical_list: D001095:Arachidonic Acids; D063388:Endocannabinoids; D008024:Ligands; D053284:Polyunsaturated Alkamides; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; C465625:cytochrome P-450 4X1; C078814:anandamide