Ox-Amylase Gene of Streptomyces limosus: Nucleotide Sequence, Expression Motifs, and Amino Acid Sequence Homology to Mammalian and Invertebrate cx-Amylases

The nucleotide sequence of the coding and regulatory regions of the ca-amylase gene (aml) of Streptomyces limosus was determined. High-resolution Si mapping was used to locate the 5' end of the transcript and demonstrated that the gene is transcribed from a unique promoter. The predicted amino acid sequence has considerable identity to mammalian and invertebrate ca-amylases, but not to those of plant, fungal, or eubacterial origin. Consistent with this is the susceptibility of the enzyme to an inhibitor of mammalian a-amylases. The amino-terminal sequence of the extracellular enzyme was determined, revealing the presence of a typical signal peptide preceding the mature form of the a-amylase.