Glucose oxidase usually occurs as a glycoprotein, with a mannose-type carbohydrate content of around 16%. However, different forms of the enzyme have been isolated, including a non-glycosylated enzyme from the fungus Phanerochaete chrysosporium. Glucose oxidase is secreted by the fungus, and is distributed between the extracellular fluid surrounding the mould, the cell wall, and in the slime mucilage. The synthesis of glucose oxidase can be induced by various substances, including molecular oxygen, which induces the transcription of the enzyme.