title: Mechanism for regulating the distribution of glucose carbon between the Embden-Meyerhof and hexose-monophosphate pathways in Streptococcus faecalis.
abstract: Glucose-adapted Streptococcus faecalis produced little if any (14)CO(2) from glucose-1-(14)C, although high levels of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) were detected in cell-free extracts. Metabolism of glucose through the oxidative portion of the hexose-monophosphate pathway was shown to be regulated in this organism by the specific inhibitory interaction of the Embden-Meyerhof intermediate, fructose-1, 6-diphosphate (FDP), with 6-phosphogluconate dehydrogenase. Glucose-6-phosphate dehydrogenase activity was unaffected by FDP. The S. faecalis 6-phosphogluconate dehydrogenase was partially purified from crude extracts by standard fractionation procedures and certain kinetic parameters of the FDP-mediated inhibition were investigated. The negative effector was shown to cause a decrease in V(max) and an increase in the apparent K(m) for both 6-phosphogluconate and nicotinamide adenine dinucleotide phosphate (NADP). These effects were apparently a consequence of the ligand interacting with the enzyme at a site distinct from either the substrate or the coenzyme sites. Among the evidence supporting this was the fact that beta-mercaptoethanol blocked completely FDP inhibition, but had no effect on catalytic activity. The possibility that the regulation of 6-phosphogluconate dehydrogenase activity by FDP might be of some general significance was suggested by the observation that this enzyme from several other sources was also sensitive to FDP.
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000096:biosynthesis; D002247:Carbon Isotopes; D002474:Cell-Free System; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D013293:Enterococcus faecalis / Q000201:enzymology / Q000378:metabolism*; D005942:Gluconates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D006168:Guinea Pigs; D006600:Hexosephosphates / Q000378:metabolism* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology; D008623:Mercaptoethanol / Q000494:pharmacology; D009249:NADP / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010734:Phosphogluconate Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D000644:Quaternary Ammonium Compounds; D012475:Salmonella / Q000201:enzymology / Q000378:metabolism; D013045:Species Specificity; D013053:Spectrophotometry; D013307:Streptomycin; D013431:Sulfates
chemical_list: D002247:Carbon Isotopes; D005942:Gluconates; D006600:Hexosephosphates; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D013431:Sulfates; D002245:Carbon Dioxide; D009249:NADP; D008623:Mercaptoethanol; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D005947:Glucose; D013307:Streptomycin