Structural insights on bioremediation of polycyclic aromatic hydrocarbons using microalgae: a modelling-based...

Area of Science:

• Bioremediation and Environmental Biotechnology
• Molecular Modeling and Structural Biology
• Biochemistry and Enzyme Function

Background:

• Microbial bioremediation struggles with degrading high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs).
• Cytochrome P450 monooxygenases (CYPs) are crucial for xenobiotic detoxification.
• The structure and function of microalgal CYPs in PAH degradation remain largely uncharacterized.

Purpose of the Study:

• To investigate the efficiency of microalgal cytochrome P450 monooxygenase (CYP) in degrading both low molecular weight (LMW) and high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs).
• To elucidate the structural basis of PAH-CYP interactions using molecular modeling.
• To identify potential microalgal candidates for effective phycoremediation of PAHs.

Main Methods:

• Protein structure modeling of microalgal CYP using available templates.
• Molecular docking of modeled CYP structures against 38 different PAH compounds.
• Analysis of binding interactions, including binding sites and modes (hydrogen bonding, hydrophobic, π-π, van der Waals).

Main Results:

• CYP from *Haematococcus pluvialis* and *Parachlorella kessleri* demonstrated broad oxidizing capability for both LMW- and HMW-PAHs.
• *P. kessleri* CYP exhibited strong binding affinity for PAHs, with a glide score of -10.23 and glide energy of -23.48 kcal/mol.
• PAHs were found to bind to CYP active sites (Lys⁶⁹, Trp⁹⁶, Gln³⁹⁷, Arg³⁹⁸) via multiple interaction types, including hydrogen bonding.

Conclusions:

• Microalgae, particularly *Parachlorella kessleri*, possess CYP enzymes capable of efficiently degrading HMW-PAHs, outperforming other microorganisms.
• The study provides structural insights into CYP-PAH interactions, identifying key binding sites and interaction forces.
• These findings establish a framework for screening microalgal species for phycoremediation potential based on CYP structure and function.