Maltose utilization in Enterococcus faecalis involves a novel maltose-6-P phosphatase

BLANCATO, VS; MOKHTARI, A; REPIZO, GD; HENRI, C; BOURAND, A; HARTKE, A; THOMPSON, J; MAGNI, C; DEUTSCHER, J

Mendoza

Congreso; XLVIII Reunión Anual de SAIB; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

In Enterococcus faecalis the genes involved in maltose metabolism are organized in a divergent fashion. The malPBMR operon encodes putative maltose phosphate phosphorylase (malP), β-phosphoglucomutase (malB), aldose-1-epimerase (malM) and transcriptional repressor (malR) whereas the malT-mapP operon codes for a PTS enzyme II (malT) and a putative maltose phosphatase (mapP). In order to confirm the role of MalP and MapP enzymes in the pathway, the corresponding genes were cloned, expressed and the recombinant proteins purified. MalP enzymatic activity was only detected when maltose was used as a substrate, indicating that it is in fact a maltose phosphorylase. Since PTS sugars are phosphorylated during transport, our hypothesis was that MapP could be responsible of intracellular maltose-6-P dephosphorylation, providing the substrate for MalP. Effectively, MapP in vitro phosphatase activity was confirmed by a spectrophotometric assay and by mass spectroscopy. Furthermore, in order to demonstrate that MapP activity in vivo, we constructed a B. subtilis mutant, devoid of the 6-P-α-glucosidase that hydrolyses maltose-6-P (MalA). MapP expression allowed this strain to grow on maltose-containing minimal medium, supporting the in vitro observations. The results presented in this work help to clarify the unusual maltose metabolism present in E. faecalis.