Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
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Enzyme
Compound
Query: EC:3.2.1.23 (
beta-galactosidase
)
14,648
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
In gram-positive bacteria, HPr, a phosphocarrier protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), is phosphorylated by an ATP-dependent, metabolite-activated protein kinase on seryl residue 46. In a Bacillus subtilis mutant strain in which Ser-46 of HPr was replaced with a nonphosphorylatable alanyl residue (ptsH1 mutation), synthesis of
gluconate kinase
, glucitol dehydrogenase, mannitol-1-P dehydrogenase and the mannitol-specific PTS permease was completely relieved from repression by glucose, fructose, or mannitol, whereas synthesis of inositol dehydrogenase was partially relieved from catabolite repression and synthesis of alpha-glucosidase and glycerol kinase was still subject to catabolite repression. When the S46A mutation in HPr was reverted to give S46 wild-type HPr, expression of
gluconate kinase
and glucitol dehydrogenase regained full sensitivity to repression by PTS sugars. These results suggest that phosphorylation of HPr at Ser-46 is directly or indirectly involved in catabolite repression. A strain deleted for the ptsGHI genes was transformed with plasmids expressing either the wild-type ptsH gene or various S46 mutant ptsH genes (S46A or S46D). Expression of the gene encoding S46D HPr, having a structure similar to that of P-ser-HPr according to nuclear magnetic resonance data, caused significant reduction of
gluconate kinase
activity, whereas expression of the genes encoding wild-type or S46A HPr had no effect on this enzyme activity. When the promoterless lacZ gene was put under the control of the gnt promoter and was subsequently incorporated into the amyE gene on the B. subtilis chromosome, expression of
beta-galactosidase
was inducible by gluconate and repressed by glucose. However, we observed no repression of
beta-galactosidase
activity in a strain carrying the ptsH1 mutation. Additionally, we investigated a ccpA mutant strain and observed that all of the enzymes which we found to be relieved from carbon catabolite repression in the ptsH1 mutant strain were also insensitive to catabolite repression in the ccpA mutant. Enzymes that were repressed in the ptsH1 mutant were also repressed in the ccpA mutant.
...
PMID:Loss of protein kinase-catalyzed phosphorylation of HPr, a phosphocarrier protein of the phosphotransferase system, by mutation of the ptsH gene confers catabolite repression resistance to several catabolic genes of Bacillus subtilis. 819 89
