Abstract
The kinetic and thermostability properties of a glucooligosaccharide oxidase from Acremonium strictum were determined. This enzyme produces only maltobionic acid from maltose. It is most active at pH 9 to 10.5, and is most stable at pH 6.5. Values of both KM and Vmax on maltose are highest at pH 10. The highest values of KM and Vmax occur with glucose, maltopentaose, and maltoheptaose, whereas the lowest values of KM are with maltotriose and of Vmax are with maltohexaose. Values of KM with any substrate and at any pH are always substantially above 1 mM. Activation energies for catalysis and thermoinactivation are 23 kJ/mol and 421 kJ/mol, respectively. The N-terminal sequence is not homologous with any other oxidase, but has some homology with other proteins having different functions. These unusual properties suggest that glucooligosaccharides may not be the primary substrates of this enzyme. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 68: 231–237, 2000.
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