Identification of a robust bacterial pyranose oxidase that displays an unusual pH dependence
Year: 2024
Type: article
Abstract: Pyranose oxidases are valuable biocatalysts, yet only a handful of bacterial pyranose oxidases are known. These bacterial enzymes exhibit noteworthy distinctions from their extensively characterized fungal counterparts, encompassing variations in substrate specificity and structural attributes. Herein a bacterial pyranose oxidase from Oscillatoria princeps ( O POx) was biochemically characterized in detail. In contrast to the fungal pyranose oxidases, O POx could be well expressed in Escherichia coli as soluble, fully flavinylated, and active oxidase. It was found to be highly thermostable (melting temperature >90 °C) and showed activity on glucose, exhibiting an exceptionally low K M value (48 μM). Elucidation of its crystal structure revealed similarities with fungal pyranose oxidases, such as being a tetramer with a large central void leading to a narrow substrate access tunnel. In the active site, the FAD cofactor is covalently bound to a histidine. O POx displays a relatively narrow pH optimum for activity with a sharp decline at relatively basic pH values which is accompanied by a drastic change in its flavin absorbance spectrum. The pH-dependent switch in flavin absorbance features and oxidase activity was shown to be fully reversible. It is hypothesized that a glutamic acid helps to stabilize the protonated form of the histidine that is tethered to the FAD. O POx presents itself as a valuable biocatalyst as it is highly robust, well-expressed in E. coli , shows low K M values for monosaccharides, and has a peculiar pH-dependent "on-off switch".
Source: Journal of Biological Chemistry
Authors: Lars L. Santema, Henriëtte J. Rozeboom, Veronica P. Borger, Saniye G. Kaya, Marco W. Fraaije
Institution: University of Groningen
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,800
OpenAlex ID: W4403295479