Nucleotide sequence of the raw-starch-digesting amylase gene from Bacillus sp. B1018 and its strong homology to the cyclodextrin glucanotransferase genes.

The gene coding for the raw-starch-digesting amylase from Bacillus sp. B1018 was cloned into Escherichia coli, and its nucleotide sequence was determined. Starting at an ATG codon, there was an open reading frame composed of 2139 bp (713 amino acids). The NH2-terminal portion encoded a 27 amino acid-long signal peptide. S1 mapping revealed the presence of a typical promoter region upstream from the transcription initiation site. The deduced amino acid sequence of the extracellular mature enzyme was very similar to those of cyclodextrin glucanotransferases (CGTases), especially that of alkalophilic Bacillus sp. 1011 (87% homology). In fact, the B1018 amylase showed CGTase activity. The COOH-terminal portion of the B1018 amylase shows significant homology with other raw-starch-digesting enzymes.