Unusual transport and utilization of maltose and maltose oligomers by Enterococcus faecalis

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

Tuscani

Congreso; 7th International Conference on Gram-positive Microorganisms; 2013

Enterococcus faecalis transports maltose mainly via the PEP:carbohydrate phosphotransferase system (PTS) permease MalT. However, in contrast to Bacillus subtilis, this organism lacks a 6-P-alpha-glucosidase, which cleaves maltose-6´-P into glucose and glucose-6-P. Instead, E. faecalis uses a novel phosphatase, MapP, that belongs to the endonuclease/exonuclease/phosphatase family and that dephosphorylates maltose-6´-P. The resulting intracellular maltose is phosphorolyzed by maltose phosphorylase (MalP) into glucose and glucose-1-P. E. faecalis contains an ABC transport system for maltodextrins, which exhibits also low affinity for maltose. A mapP mutant was therefore still able to grow on maltose, although at significantly slowed rate compared to the wild-type strain, whereas a malP mutant was unable to utilize maltose. The mapP mutant accumulated maltose-6?-P whereas a malP mutant accumulated mostly unphosphorylated maltose. When synthesized in B. subtilis the E. faecalis MapP protein restored growth of a malA mutant on maltose. Similar MapP-requiring maltose utilzation systems are present in most other enterococci and most streptococci as well as in several bacilli and clsotridia. The MalT proteins of these organisms also seem to efficiently transport maltotriose. Accordingly E. faecalis MapP dephosphorylates maltotriose-6´´-P at about 25% of the velocity measured with maltose-6´-P. The resulting intracellular maltotriose is probably stepwise phosphorolyzed by the enzyme MalP.