AUTHOR=Perera Madushika , Wijesundera Sulochana , Wijayarathna C. Dilrukshi , Seneviratne Gamini , Jayasena Sharmila 

TITLE=Identification of long-chain alkane-degrading (LadA) monooxygenases in Aspergillus flavus via in silico analysis

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.898456

DOI=10.3389/fmicb.2022.898456

ISSN=1664-302X

ABSTRACT=<p>Efficient degradation of alkanes in crude oil by the isolated <italic>Aspergillus flavus</italic> MM1 alluded to the presence of highly active alkane-degrading enzymes in this fungus. A long-chain alkane-degrading, LadA-like enzyme family in <italic>A. flavus</italic> was identified, and possible substrate-binding modes were analyzed using a computational approach. By analyzing publicly available protein databases, we identified six uncharacterized proteins in <italic>A. flavus</italic> NRRL 3357, of which five were identified as class LadAα and one as class LadAβ, which are eukaryotic homologs of bacterial long-chain alkane monooxygenase (LadA). Computational models of <italic>A. flavus</italic> LadAα homologs (<italic>Af1-Af5</italic>) showed overall structural similarity to the bacterial LadA and the unique sequence and structural elements that bind the cofactor Flavin mononucleotide (FMN). A receptor-cofactor-substrate docking protocol was established and validated to demonstrate the substrate binding in the <italic>A. flavus</italic> LadAα homologs. The modeled <italic>Af1</italic>, <italic>Af3, Af4</italic>, and <italic>Af5</italic> captured long-chain <italic>n</italic>-alkanes inside the active pocket, above the bound FMN. Isoalloxazine ring of reduced FMN formed a π–alkyl interaction with the terminal carbon atom of captured alkanes, C<sub>16</sub>–C<sub>30</sub>, in <italic>Af</italic>3–<italic>Af</italic>5 and C<sub>16</sub>–C<sub>24</sub> in <italic>Af</italic>1. Our results confirmed the ability of identified <italic>A. flavus</italic> LadAα monooxygenases to bind long-chain alkanes inside the active pocket. Hence <italic>A</italic>. <italic>flavus</italic> LadAα monooxygenases potentially initiate the degradation of long-chain alkanes by oxidizing bound long-chain alkanes into their corresponding alcohol.</p>