Substrate specificities of aromatic ring-hydroxylating oxygenases of an uncultured gammaproteobacterium from chronically-polluted Subantarctic sediments

MUSUMECI, MATIAS; LOVISO, CLAUDIA L.; LOZADA, MARIANA; FERREIRA, FLAVIA; DIONISI, HEBE

INTERNATIONAL BIODETERIORATION & BIODEGRADATION

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2019 vol. 137

0964-8305

Aromaticring-hydroxylating oxygenases (RHOs) are multicomponent enzymes thatcatalyze the vicinal hydroxylation of aromatic rings to producecis-dihydrodiols,a key step in the aerobic biodegradation of aromatic compounds. Inthis work, we describe the characterization of three RHOs of anuncultured gammaproteobacterium from chronically pollutedSubantarctic intertidal sediments. Sequences encoding the α and βsubunits of these RHOs, classified as class A type III, and one setof the corresponding electron transfer partners, were identified in a34 Kb fragment from a metagenomic fosmid library. Structural modelingand docking analyses suggested that the active sites of these enzymesaccommodated different set of substrates. The three enzymes,including the electron transfer components, were expressed inEscherichiacoli andpurified. The enzyme with the largest predicted catalytic pocket andwider diameter channels presented a remarkably relaxed substratespecificity, including 2-4 ring PAHs (phenanthrene, pyrene,fluoranthene and naphthalene). The other two RHOs were stricter intheir substrate specificity, and hydroxylated biphenyl andnaphthalene more efficiently. These results suggest the evolution ofcompatible RHO enzymes within a single catabolic gene cluster in thismicroorganism. This work increases our understanding of thePAH-degrading capabilities of uncultured bacteria from cold coastalenvironments.p { margin-bottom: 0.25cm; line-height: 115%; background: transparent none repeat scroll 0% 0%; }