Glucose oxidase from Aspergillus niger: the mechanism of action with molecular oxygen, quinones, and one-electron acceptors

The active site of the enzyme contains, in addition to FAD, three amino acid side chains that are intimately involved in catalysis: His516 with a pKa = 6.9, and Glu412 with pKa = 3.4 which is hydrogen bonded to His559, with pKa > 8. The protonation of each of these residues has a strong influence on all rate constants in the catalytic mechanism.