Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of beta-galactosidase in transcriptional fusions with the pps gene (encoding phosphoenolpyruvate [PEP] synthase), the aceBAK operon (encoding malate synthase, isocitrate lyase, and isocitrate dehydrogenase kinase, respectively), and the phs operon (encoding either thiosulfate reductase or a regulatory protein controlling its expression) was studied in Salmonella typhimurium. beta-Galactosidase synthesis in these strains was repressible either by growth in the presence of glucose or by the presence of a fruR mutation, which resulted in the constitutive expression of the fructose (fru) regulon. Five enzymes of gluconeogenesis (PEP synthase, PEP carboxykinase, isocitrate lyase, malate synthase, and fructose-1,6-diphosphatase) were shown to be repressed either by growth in the presence of glucose or the fruR mutation, while the glycolytic enzymes, enzyme I and enzymes II of the phosphotransferase system as well as phosphofructokinase, were induced either by growth in the presence of glucose or the fruR mutation. Overexpression of the cloned fru regulon genes (not including fruR) resulted in parallel repression of representative gluconeogenic, Krebs cycle, and glyoxylate shunt enzymes. Studies with temperature-sensitive mutants of S. typhimurium which synthesized heat-labile IIIFru proteins provided evidence that this protein plays a role in the regulation of gluconeogenic substrate utilization. Other mutant analyses revealed a complex relationship between fru gene expression and the expression of genes encoding gluconeogenic enzymes. Taken together, the results suggest that a number of genes encoding catabolic, biosynthetic, and amphibolic enzymes in enteric bacteria are transcriptionally regulated by a complex catabolite repression/activation mechanism which may involve enzyme IIIFru of the phosphotransferase system as one component of the regulatory system.
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PMID:Altered transcriptional patterns affecting several metabolic pathways in strains of Salmonella typhimurium which overexpress the fructose regulon. 249 6

Salmonella typhimurium produces H2S from thiosulfate or sulfite. The respective pathways for the two reductions must be distinct as mutants carrying motations in phs, chlA, and menB reduced sulfite, but not thiosulfate, to H2S, and glucose repressed the production of H2S from thiosulfate while it stimulated its production from sulfite. The phs and chlA mutants also lacked a methyl viologen-linked thiosulfate reductase activity present in anaerobically grown wild-type cultures. A number of hydroxylamine, transposon Tn10 insertion, and Mu d1(Apr lac) operon fusion mutants defective in phs were characterized. One of the hydroxylamine mutants was an amber mutant, as indicated by suppression of its mutation in a supD background. The temperature-sensitive phs mutants produced H2S and methyl viologen-linked thiosulfate reductase at 30 degrees C but not at 42 degrees C. The reductases in all such mutants grown at 30 degrees C were as thermostable as the wild-type enzyme and did not differ in electrophoretic relative mobility, suggesting that phs is not the structural gene for thiosulfate reductase. Expression of beta-galactosidase in phs::Mu d1(Apr lac) mutants was dependent on anaerobiosis and the presence of reduced sulfur. It was also strongly influenced by carbon source and growth stage. The results are consistent with a model in which the phs gene encodes a regulatory protein essential for the reduction of thiosulfate to hydrogen sulfide.
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PMID:The phs gene and hydrogen sulfide production by Salmonella typhimurium. 310 33

The Salmonella typhimurium phs chromosomal locus essential for the reduction of thiosulfate to hydrogen sulfide was cloned, and some features of its regulation were examined. The phs locus conferred H2S production on Escherichia coli, suggesting that it contains the structural gene for thiosulfate reductase. H2S production by the E. coli host was, as in S. typhimurium, suppressed by nitrate or glucose in the growth medium. The presence of plasmid-borne phs genes in a S. typhimurium chl+ host containing a chromosomal phs::lacZ operon fusion was found to significantly increase the relative induction efficiency of beta-galactosidase by thiosulfate. These results are consistent with a model for phs regulation in which the true inducer is not thiosulfate per se and in which the action of a phs-encoded molybdoprotein, possibly the reductase itself, converts thiosulfate into a compound that resembles the true inducer more closely than does thiosulfate.
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PMID:Cloning of the phs genetic locus from Salmonella typhimurium and a role for a phs product in its own induction. 840 12