BACKGROUND: Cytochromes P450 are major drug-metabolizing enzymes involved in the biotransformation of diverse xenobiotics and endogenous chemicals. Persistent organic pollutants (POPs) are toxic hydrophobic compounds that cause serious environmental problems because of their poor degradability. This calls for rational design of enzymes capable of catalyzing their biotransformation. Cytochrome P450 1A1 isoforms catalyze the biotransformation of some POPs, and constitute good starting points for the design of biocatalysts with tailored substrate specificity. METHODS: We rationalized the activities of wild type and mutant forms of rat cytochrome P450 1A1 towards 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) and 3,3',4,4'-tetrachlorobiphenyl (PCB77) using experiments and molecular dynamics simulations. RESULTS: We showed that the enhanced activity of the CYP1A1 mutant towards TCDD was due to more efficient binding of the substrate in the active site even though the mutated site was over 2.5nm away from the catalytic center. Moreover, this mutation reduced activity towards PCB77. GENERAL SIGNIFICANCE: Amino acids that affect substrate access channels can be viable targets for rational enzyme design even if they are located far from the catalytic site.

Biosignal Research Center Kobe University Kobe Hyogo 657 8501 Japan

Biotechnology Research Center Faculty of Engineering Toyama Prefectural University Imizu Toyama 939 0398 Japan

Graduate School of Agricultural Science Kobe University Kobe Hyogo 657 8501 Japan

Hyogo Prefectural Institute of Environmental Sciences Kobe Hyogo 654 0037 Japan

Regional Centre of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacký University Olomouc tř 17 listopadu 12 771 46 Olomouc Czech Republic

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