A bacterial cold-active dye-decolorizing peroxidase from an Antarctic Pseudomonas strain

Abstract

DyP (dye-decolorizing peroxidase) enzymes are hemeproteins that catalyze the H₂O₂-dependent oxidation of various molecules and also carry out lignin degradation, albeit with low activity. We identified a dyp gene in the genome of an Antarctic cold-tolerant microbe (Pseudomonas sp. AU10) that codes for a class B DyP. The recombinant protein (rDyP-AU10) was produced using Escherichia coli as a host and purified. We found that rDyP-AU10 is mainly produced as a dimer and has characteristics that resemble psychrophilic enzymes, such as high activity at low temperatures (20 °C) when using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and H₂O₂ as substrates, thermo-instability, low content of arginine, and a catalytic pocket surface larger than the DyPs from some mesophilic and thermophilic microbes. We also report the steady-state kinetic parameters of rDyP-AU10 for ABTS, hydroquinone, and ascorbate. Stopped-flow kinetics revealed that Compound I is formed with a rate constant of (2.07 ± 0.09) × 10⁶ M^-1 s^-1 at pH 5 and that this is the predominant species during turnover. The enzyme decolors dyes and modifies kraft lignin, suggesting that this enzyme may have potential use in bioremediation and in the cellulose and biofuel industries. KEY POINTS: • An Antarctic Pseudomonas strain produces a dye-decolorizing peroxidase. • The recombinant enzyme (rDyP-AU10) was produced in E. coli and purified. • rDyP-AU10 showed high activity at low temperatures. • rDyP-AU10 is potentially useful for biotechnological applications.

Keywords: Antarctica; Bioremediation; Cold-active enzyme; Dye-decolorizing peroxidase; Lignin modification.