title: Irreversibel inactivation of the membrane-bound enzyme IIlac of the lactose phosphotransferase system of Staphylococcus aureus by triton X-100 and protection by substrates.
abstract: Enzyme IIlac, the membrane-bound component of the lactose phosphotransferase system of Staphylococcus aureus, catalyzes the phosphorylation-transport reaction below: (see article).  (The sugar can be lactose or one of its analogs.) The effects of the non-ionic detergents Triton X-100, Brij 35, and Tween 40 on the activity of Enzyme IIlac were studied. Especially striking effects were observed using Triton X-100, a detergent previously used to solubilize and isolate this enzyme. A systematic study of Triton effects over a range of concentrations and temperatures demonstrated three aspects of Triton-membrane interaction. At 0.1% Triton and 25 degrees C Enzyme IIlac is activated, but remains particulate. At 0.5% Triton and 0.5% Triton and 37 degrees C, it is rapidly and irreversibly inactivated. Sugar substrates and inhibitory sugar analogs protect Enzyme IIlac against inactivation; the effect is specific for beta-galactosides. The other substrate of Enzyme IIlac, phospho-Factor IIIlac, does not affect Triton inactivation, and the product analog galactose 6-phosphate slightly enhances the inactivation rate.
mesh_terms: D003902:Detergents / Q000494:pharmacology; D005690:Galactose / Q000494:pharmacology; D005697:Galactosides / Q000494:pharmacology*; D006027:Glycosides / Q000494:pharmacology*; D007700:Kinetics; D010710:Phosphates; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011136:Polysorbates / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000201:enzymology*
chemical_list: D003902:Detergents; D005697:Galactosides; D006027:Glycosides; D010710:Phosphates; D011136:Polysorbates; D000644:Quaternary Ammonium Compounds; D011092:Polyethylene Glycols; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005690:Galactose