Immobilization of the enzyme GpdQ on magnetite nanoparticles for organophosphate pesticide bioremediation

•Mutant of glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes is reported.•The mutant has been immobilized on PAMAM dendrimer-modified magnetite nanoparticles.•A kinetic assay has been designed using organophosphoester substrates.•GpdQ was successfully immobilized on the nanoparticles and active for multiple cycles.

Annually thousands of people die or suffer from organophosphate (pesticide) poisoning. In order to remove these toxic compounds from the environment, the use of enzymes as bioremediators has been proposed. We report here a Ser127Ala mutant based on the enzyme glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes. The mutant, with improved metal binding abilities, has been immobilized using glutaraldehyde on PAMAM dendrimer-modified magnetite nanoparticles. The immobilized system was characterized using elemental analysis as well as infrared, transmission electron and X-ray photoelectron spectroscopies. The amount of GpdQ that was immobilized with the optimized procedure was 1.488 nmol per g MNP. A kinetic assay has been designed to evaluate the activity of the system towards organophosphoester substrates. The specific activity towards BPNPP directly after immobilization was 3.55 μmol mg− 1 min− 1, after one week 3.39 μmol mg− 1 min− 1 and after 120 days 3.36 μmol mg− 1 min− 1, demonstrating that the immobilized enzyme was active for multiple cycles and could be stored on the nanoparticles for a prolonged period.

Graphical abstractWe report that a mutant with improved metal binding abilities and based on the enzyme glycerophosphodiesterase (GpdQ) from Enterobacter aerogenes has been immobilized on modified magnetite nanoparticles. The enzyme was successfully immobilized on the nanoparticles, was active for multiple cycles and could be stored on the nanoparticles for a prolonged period.Figure optionsDownload full-size imageDownload as PowerPoint slide