Cloning and sequencing of an original gene encoding a maltogenic amylase from Bacillus sp US149 strain and characterization of the recombinant activity

A gene encoding maltogenic amylase from acidic Bacillus sp. US149 (maUS149) was cloned, sequenced and over-expressed in Escherichia coli. The nucleotide sequence analysis revealed an open reading frame (ORF) of 1749 bp encoding a protein of 582 residues. The alignment of deduced amino acid sequence revealed a relatively low homology with the already reported maltogenic amylases. In fact, its highest identity, of only 60%, was found with the maltogenic amylase of Thermus sp. IM6501. The recombinant enzyme (MAUS149) was found to be intracellular and was purified to homogeneity from the cell crude extract with a yield of 23%. According to PAGE analysis, under reducing and non-reducing conditions, the recombinant enzyme has an apparent molecular weight of 135 kDa and is composed of two identical subunits of 67.5 kDa each. The maximum activity was obtained at 40 degrees C and pH 6.5. MAUS149 could be classified as a maltogenic amylase since it produces mainly maltose from starch, maltose and glucose from beta-cyclodextrin, and panose from pullulan.