A glutathione peroxidase from Antarctic psychrotrophic bacterium Pseudoalteromonas sp. ANT506: Cloning and heterologous expression of the gene and characterization of recombinant enzyme.

A glutathione peroxidase (GPx) gene, designated as PsGPx, was cloned from Antarctic psychrotrophic bacterium Pseudoalteromonas sp. ANT506 and expressed in Escherichia coli. The full-length PsGPx contained a 585-bp encoding 194 amino acids with predicted molecular masses of approx. 21.7 kDa. Multiple sequence alignments revealed that PsGPx belonged to the thioredoxin-like superfamily. PsGPx was heterologously overexpressed in E. coli, purified and characterized. The maximum catalytic temperature and pH value for recombinant PsGPx (rPsGPx) were 30°C and pH 9.0, respectively. rPsGPx retained 45% of the maximum activity at 0°C and exhibited high thermolability with a half-life of approx. 40 min at 40°C. In addition, the enzymatic activity of rPsGPx was still manifested under 3 M NaCl. The Km and Vmax values of the recombinant enzyme using GSH and H2O2 as substrates were 1.73 mM and 16.28 nmol/mL/min versus 2.46 mM and 21.50 nmol/mL/min, respectively.