Cloning, expression, and carbon catabolite repression of the bamM gene encoding beta-amylase of Bacillus megaterium DSM319

The bamM gene from Bacillus megaterium DSM319 encoding an extracellular bet a -amylase was isolated and completely sequenced. Chromosomal inactivation by deletion mutagenesis resulted in total loss of amylolytic activity, indi cative of a single starch-degrading enzyme. Functional characterization of the expressed protein revealed a maltogenic enzyme exhibiting optimal activ ities at pH 7.5 and 50 degreesC. Amylase expression is subject to catabolit e repression by glucose. A putative cis-acting catabolite-responsive elemen t (CRE) was identified; it is located within the bamM coding region, matchi ng the position of the predicted signal peptide processing site. Base subst itutions introduced by site-directed mutagenesis within the bamM-CRE - reta ining unchanged the amino acid sequence - provoked a remarkable relief from carbon catabolite repression (CCR), thereby proving functionality of the C RE for CCR.