title: The mechanism of inactivation of glucose oxidase from Penicillium amagasakiense under ambient storage conditions.
abstract: Glucose oxidase (GOx) from Penicillium amagasakiense has a higher specific activity than the more commonly studied Aspergillus niger enzyme, and may therefore be preferred in many medical and industrial applications. The enzyme rapidly inactivates on storage at pH 7.0-7.6 at temperatures between 30 and 40°C. Results of fluorimetry and circular dichroism spectroscopy indicate that GOx inactivation under these conditions is associated with release of the cofactor FAD and molten globule formation, indicated by major loss of tertiary structure but almost complete retention of secondary structure. Inactivation of GOx at pH<7 leads to precipitation, but at pH ≥ 7 it leads to non-specific formation of small soluble aggregates detectable by PAGE and size-exclusion chromatography (SEC). Inactivation of P. amagasakiense GOx differs from that of A. niger GOx in displaying complete rather than partial retention of secondary structure and in being promoted rather than prevented by NaCl. The contrasting salt effects may reflect differences in the nature of the interface between subunits in the native dimers and/or the quantity of secondary structure loss upon inactivation.
authors: School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK.
authors: Michael S
authors: MS
authors: Caves
authors: Barry K
authors: BK
authors: Derham
authors: Jan
authors: J
authors: Jezek
authors: Robert B
authors: RB
authors: Freedman
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D004795:Enzyme Stability; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D005949:Glucose Oxidase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D009994:Osmolar Concentration; D010407:Penicillium / Q000201:enzymology*; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
chemical_list: D005656:Fungal Proteins; D005182:Flavin-Adenine Dinucleotide; D005949:Glucose Oxidase