Effect of deglycosylation on the mediated electrocatalytic activity of recombinantly expressed Agaricus meleagris pyranose dehydrogenase wired by osmium redox polymer

The effect of deglycosylation of pyranose dehydrogenase (PDH) obtained from Agaricus meleagris (Am) and recombinantly expressed in Pichia pastoris on its electrocatalytic activity was investigated. Glycosylated (gAmPDH) and deglycosylated PDH (dgAmPDH) were immobilised on spectrographic graphite (G) simultaneously with an osmium redox polymer (Os-RP) using poly(ethylene glycol)(400) diglycidyl ether (PEGDGE) as cross-linking agent. The amperometric response to glucose, recorded at G/(Os-RP)-gAmPDH and G/(Os-RP)-dgAmPDH bioelectrodes, was optimised under flow injection conditions concerning the applied potential, enzyme loading, working pH and flow rate. The G/(Os-RP)dgAmPDH bioelectrode is characterised by better kinetic and electroanalytical parameters compared with the G/(Os-RP)-gAmPDH bioelectrode: (i) a higher value of the maximum catalytic current density, j(max) = (146.6 +/- 2.6) mu A cm(-2) vs. j(max) = (80.9 +/- 1.9) mu A cm(-2); (ii) a lower value of the apparent Michaelis-Menten constant, K-M(app) = (2.4 +/- 0.1) mu M vs. K-M(app) = (7.5 +/- 0.3) mM; (iii) a higher slope of the linear domain, (43.6 +/- 1.1) mu A cm(-2) mM(-1) vs. (9.74 +/- 0.16) mu A cm(-2) mM(-1). Additionally, the time dependent decay of the amperometric response to glucose shows a slightly better operational stability for the G/(Os-RP)-dgAmPDH bioelectrode than that for the G/(Os-RP)-gAmPDH. The enzyme deglycosylation induces significant changes in the order of substrate selectivity for gAmPDH and dgAmPDH. (C) 2013 Elsevier Ltd. All rights reserved.