A cDNA library from Aspergillus niger strain NRRL‐3 enriched in sequences encoding the glucose oxidase was constructed. An 800 bp cDNA clone isolated from this library was used to screen 12 000 recombinant phages from an EMBL3 genomic library. A 15 kbp DNA segment isolated from this library contained the 1815 bp structural gene for glucose oxidase as well as a short 5′‐ and a longer 3′‐noncoding region. The deduced protein sequence was verified by partial peptide sequencing.

A gene encoding glucose dehydrogenase of Bacillus megaterium M1286 was isolated from a λ‐EMBL3 phage library. It is transcribed and translated in cells of the heterologous organism Escherichia coli by own control regions. The gene is located on a 1126‐bp HindIII fragment. Its nucleotide sequence contains 220 bp in the 5′ non‐coding region, 783 bp in the coding region and 123 bp in the 3′ non‐coding region. The amino acid sequence, as deduced from the coding region, consists of 261 amino acids and is different from the known protein sequence of glucose dehydrogenase from B. megaterium M1286. [Jany, K. D., Ulmer, W., Fröschle, M. & Pfleiderer, G. (1984) FEBS Lett. 165, 6–10]. By using this gene as a hybridization probe a second glucose dehydrogenase gene was isolated, which was also directly expressed in E. coli. Additionally a DNA region with extended sequence homology to the hybridization probe was identified. This work indicates the existence of at least two independent glucose dehydrogenase genes in B. megaterium M1286. Homologies in the primary structures of the two different glucose dehydrogenases of B. megaterium M1286 and of the corresponding Bacillus subtilis enzyme are discussed.