title: beta-D-phosphogalactoside galactohydrolase of Streptococcus faecalis and the inhibition of its synthesis by glucose.
abstract: The lactose hydrolysing system of Streptococcus faecalis is described. It is closely related to that one of the group N streptocci as it consists of a beta-D-phosphogalactoside galactohydrolase (beta-Pgal). The uptake of methyl-beta-D-thiogalactoside (TMG), lactose, and glucose is maintained by the phosphoenolpyruvate-dependent phosphotransferase system (PTS) but the uptake of galactose is not. The induction time is 6--7 min. Inducers are lactose and galactose but not isopropyl-beta-D-galactoside (IPTG) and TMG. In the presence of glucose, mannose, and maltose no induction of beta-Pgal occurs but pyruvate and glycerol allow induction. The competitive inhibition of uptake of TMG by glucose suggests inducer exclusion by this sugar. TMG accumulates in the cells exclusively as a derivative.
mesh_terms: D013293:Enterococcus faecalis / Q000201:enzymology* / Q000378:metabolism; D004790:Enzyme Induction; D004794:Enzyme Repression; D005690:Galactose / Q000378:metabolism; D005695:Galactosephosphates; D005696:Galactosidases / Q000096:biosynthesis*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D005990:Glycerol / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D013862:Thiogalactosides / Q000378:metabolism; D001616:beta-Galactosidase / Q000096:biosynthesis*
chemical_list: D005695:Galactosephosphates; D011773:Pyruvates; D013862:Thiogalactosides; D005696:Galactosidases; D001616:beta-Galactosidase; D005947:Glucose; D007785:Lactose; D005990:Glycerol; D005690:Galactose