Biosensors & Bioelectronics 8 (1993) 197-203 The 3D structure of glucose oxidase from Aspergillus niger. Implications for the use of GOD as a biosensor enzyme H.J. Hecht & D. Schomburg* Gesellschaft fiir Biotechnologische Forschung (GBF), Department of Molecular Structure Research, Mascheroder Weg 1, D(W)-3300 Braunschweig, Germany H. Kalisz & R.D. Schmid Gesellschaft fir Biotechnologische Forschung (GBF), Department of Enzyme Technology, Mascheroder Weg 1, D(W)-3300 Braunschweig, Germany Abstract: The tertiary structure of glucose oxidase (GOD) from Aspergiflus niger was determined by x-ray crystallography (to be described elsewhere). The overall folding of the enzyme is described with regard to its application in biosensors, and conclusions are drawn from experiments on electrical communication between the enzyme and the electrodes. Keywords: glucose oxidase, x-ray crystallography, protein 3D structure, biosensor. 1. INTRODUCTION Glucose oxidase (P-D-glucose:oxygen l-oxido- reductase, EC 1.1.3.4.) catalyses the oxidation of P-D-glucose to D-glucono-1 $lactone and hydrogen peroxide, using molecular oxygen. It is a dimeric protein with a molecular weight of 160 kDa, containing one tightly bound flavin adenine dinucleotide (FAD) per monomer as co-factor. The enzyme is glycosylated, with a carbohydrate content of 16%. * To whom correspondence should be addressed. Since Clark & Lyons (1962) described the first specific glucose electrode based on glucose oxidase, glucose oxidase has become the prime goal of the development of biosensors for several different applications in biotechnology and medi- cine (e.g., the quantitative analysis of glucose in blood). The developed glucose sensors ampero- metrically measure the production of H202 in the enzyme membrane covering a modified Clark electrode, or use chemically modified electrodes with a low-molecular-weight mediator integrated into the amperometric electrode. The most suc- cessful mediator-modified electrode has been developed by the use of ferrocene derivatives 0956-5663/93/$06.00 0 1993 Elsevier Science Publishers Ltd. 197