Identification and Enzymatic Characterization of the Maltose-Inducible α-Glucosidase MalL (Sucrase-Isomaltase-Maltase) of Bacillus subtilis

A gene coding for a putative α-glucosidase has been identified in the open reading frame yvdL (now termed malL), which was sequenced as part of the Bacillus subtilis genome project. The enzyme was overproduced in Escherichia coli and purified. Further analyses indicate that MalL is a specific oligo-1,4-1,6-α-glucosidase (sucrase-maltase-isomaltase). MalL expression in B. subtilis requires maltose induction and is subject to carbon catabolite repression by glucose and fructose. Insertional mutagenesis of malL resulted in a complete inactivation of the maltose-inducible α-glucosidase activity in crude protein extracts and a Mal⁻ phenotype.