GLUCOSE oxidase was discovered by Müller1,2 in Aspergillus niger and Penicillium glaucum. He found that this enzyme catalyses the oxidation of glucose to gluconic acid by means of molecular oxygen, and that at a much slower rate it also oxidizes mannose and galactose but not other sugars. The activity of the enzyme was found by him not to be affected by cyanide. The enzyme was reinvestigated by Franke and Lorenz3 and by Franke and Deffner4 Who, working with a more purified enzyme preparation, demonstrated that during the catalytic oxidation of glucose to gluconic acid oxygen is reduced to hydrogen peroxide. They found also a certain proportionality between the activities of different preparations and their flavin content, and concluded that the enzyme must be a flavoprotein. More recently, Coulthard, Michaelis, Short, Sykes, Skrimshire, Standfast, Birkinshaw and Raistrick5, while investigating the antibacterial properties developing in culture media of Penicillium notatum, were able to isolate a substance described by them as notatin. They identified this substance as glucose oxidase and showed that the marked antibacterial property which it exhibits in presence of glucose and air is due to hydrogen peroxide produced by the reduction of atmospheric oxygen. They isolated and purified the enzyme on a large scale and obtained a product which can be considered as pure glucose oxidase. This enabled them to re-determine its properties and to establish its flavoprotein nature. They did not, however, determine the exact structure of its prosthetic group, although they suggested that it “could readily be determined whether notatin is of alloxazine-adenine-dinucleotide type by testing it for enzyme activity in the d-amino acid oxidase system”.