Identification of New Dioxygenases Able to Recognize Polycyclic Aromatic Hydrocarbons with High Aromaticity

Polycyclic aromatic hydrocarbons (PAHs), products from the incomplete combustion of crude oil, are pollutants present in nature. Ring hydroxylating dioxygenase enzymes are able to catalyze polycyclic aromatic hydrocarbons in the biodegradation process with a high degree of stereo-, regio-, and enantiospecificity. In this work, we present the first approximation of the binding modes of 9 PAHs with high aromaticity in the catalytic sites of biphenyl or naphthalene dioxygenases from four microorganisms usually used in bio-remediation processes: Sphingobium yanoikuyae, Rhodococcus jostii RHA1, Pseudomonas sp. C18, and Paraburkholderia xenovorans. Molecular modeling studies of two biphenyl dioxygenases from Sphingobium yanoikuyae and Paraburkholderia xenovorans showed good binding affinity for PAHs with 2-4 benzene rings (fluoranthene, pyrene, and chrysene), and both enzymes had a similar amount of substrate binding. Molecular docking studies using naphthalene dioxygenase from Pseudomonas sp. C18 showed that the enzyme is able to accommodate PAHs with high aromaticity (benzo(a)pyrene, indeno(1,2,3-cd)pyrene), with good docking scores. This study provides important insight into the utility of naphthalene dioxygenases in the degradation of HAPs with high aromaticity.

Automated summary

This study provides insights into the binding modes of dioxygenases with PAHs and demonstrates their catalytic efficiencies towards PAHs with 2-4 benzene rings. Additionally, it shows that naphthalene dioxygenase can accommodate PAHs with high aromaticity and has good docking scores.