Enterococcus faecalis utilizes maltose by connecting two incompatible metabolic routes via a novel maltose 6phosphate phosphatase (MapP)

BLANCATO VICTOR,; CH. MAGNI,

MOLECULAR MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 p. 234 - 253

0950-382X

Similar to Bacillus subtilis, Enterococcus faecalistransports and phosphorylates maltose via a phosphoenolpyruvate(PEP):maltose phosphotransferasesystem (PTS). The maltose-specific PTS permease isencoded by the malT gene. However, E. faecalis lacksa malA gene encoding a 6-phospho-alpha-glucosidase,which in B. subtilis hydrolyses maltose 6-P intoglucose and glucose 6-P. Instead, an operon encodinga maltose phosphorylase (MalP), a phosphoglucomutaseand a mutarotase starts upstream from malT.MalP was suggested to split maltose 6-P into glucose1-P and glucose 6-P. However, purified MalP phosphorolysesmaltose but not maltose 6-P. We discoveredthat the gene downstream from malT encodes a novelenzyme (MapP) that dephosphorylates maltose 6-Pformed by the PTS. The resulting intracellular maltoseis cleaved by MalP into glucose and glucose 1-P. Slowuptake of maltose probably via a maltodextrin ABCtransporter allows poor growth for the mapP but notthe malP mutant. Synthesis of MapP in a B. subtilismutant accumulating maltose 6-P restored growth onmaltose. MapP catalyses the dephosphorylation ofintracellular maltose 6-P, and the resulting maltose isconverted by the B. subtilis maltose phosphorylaseinto glucose and glucose 1-P. MapP therefore connectsPTS-mediated maltose uptake to maltosephosphorylase-catalysed metabolism. Dephosphorylationassays with a wide variety of phosphosubstratesrevealed that MapP preferablydephosphorylates disaccharides containing an O-aglycosyllinkage.