The amino acid sequence of glucose dehydrogenase from Bacillus megaterium has been determined. The enzyme consists of 4 identical subunits, each containing 262 amino acid residues. Its structure was established using manual Edman degradation procedures after modification of the enzyme in the native form with reagents specific to the amino acids histidine, tyrosine, tryptophan and lysine in order to identify residues involved in catalysis or located in the subunit binding area.