Isolation, purification and characterization of a novel glucose oxidase from Penicillium sp. CBS 120262 optimally active at neutral pH

A novel glucose oxidase (GOX), a flavoenzyme, from Penicillium sp. was isolated, purified and partially characterised. Maximum activities of 1.08 U mg−1dry weight intracellular and 6.9 U ml−1 extracellular GOX were obtained. Isoelectric focussing revealed two isoenzymes present in both intra- and extracellular fractions, having pI's of 4.30 and 4.67. GOX from Penicillium sp. was shown to be dimeric with a molecular weight of 148 kDa, consisting of two equal subunits with molecular weight of 70 kDa. The enzyme displayed a temperature optimum between 25 and 30 °C, and an optimum pH range of 6-8 for the oxidation of β-d-glucose. The enzyme was stable at 25 °C for a minimum of 10 h, with a half-life of approximately 30 min at 37 °C without any prior stabilisation. The lyophilized enzyme was stable at −20 °C for a minimum of 6 months. GOX from Penicillium sp. Tt42 displayed the following kinetic characteristics: Vmax, 240.5 U mg−1; Km, 18.4 mM; kcat, 741 s−1 and kcat/Km, 40 s−1 mM−1. Stability at room temperature, good shelf-life without stabilisation and the neutral range for the pH optimum of this GOX contribute to its usefulness in current GOX-based biosensor applications.