FEMS microbiology letters

Maltose metabolism of Lactobacillus sanfranciscensis: cloning and heterologous expression of the key enzymes, maltose phosphorylase and phosphoglucomutase.

PMID 9851037


The maltose degradation operon containing genes encoding maltose phosphorylase mapA and phosphoglucomutase pgmA from Lactobacillus sanfranciscensis DSM20451T were cloned and expressed in Escherichia coli. These genes represent the first genetic data available for this species beyond taxonomic classification. MapA encodes a 754-amino acid polypeptide representing maltose phosphorylase, MapA, with a calculated molecular mass of 85.7 kDa. Comparative sequence analysis showed that mapA is of a new type distinct from other alpha-glucosidase genes sequenced so far. Putatively, pyridoxal 5'-phosphate is required as cofactor. The deduced amino acid sequence of pgmA shows an overall similarity of 39% to the phosphoglucomutase of Lactococcus lactis. pgmA is separated by a single nucleotide from the preceding mapA gene indicating effective translation by translational coupling. Upon subcloning mapA was heterologously expressed in E. coli. Additionally, upstream of the maltose-degrading operon ORF1 and ORF2 are located in the opposite direction. These genes show homology to fabZ and accB from E. coli and Bacillus subtilis, respectively, both involved in fatty acids biosynthesis.

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