The fluorescence emission of the apo-glucose oxidase from Aspergillus niger as probe to estimate glucose concentrations

We developed a new method of glucose sensing using an inactive form of glucose oxidase from Aspergillus niger. Glucose oxidase was rendered inactive by removal of the FAD cofactor. The resulting ape-glucose oxidase still binds glucose as observed from a decrease in its intrinsic tryptophan fluorescence. 8-Anilino-1-naphthalenesulfonic acid (ANS) was found to bind spontaneously to ape-glucose oxidase as seen from an enhancement of the ANS fluorescence. The steady state intensity of the bound ANS decreased 25% upon binding of glucose, and the mean lifetime of the bound ANS decreased about 40%. These spectral changes occurred with a midpoint from 10 to 20 mM glucose, which is comparable to the KD of hole-glucose oxidase. These results suggest that ape-glucose oxidase can be used as a reversible nonconsuming sensor for glucose. (C) 1999 Academic Press.