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Evidence for the Functional Association of Enzyme I and HPr of the Phosphoenolpyruvate‐Sugar Phosphotransferase System With the Membrane in Sealed Vesicles of Escherichia coli
Author(s) -
Saier Milton H.,
Cox David F.,
Feucht Brigette U.,
Novotny Michael J.
Publication year - 1982
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.1982.240180210
Subject(s) - pep group translocation , phosphoenolpyruvate carboxykinase , enzyme , biochemistry , vesicle , chemistry , membrane , phosphotransferase , enzyme assay , sugar , cell membrane
Several independent assay procedures were used to estimate the activities of the enzyme constituents of the phosphoenolpyruvate‐sugar phosphotransferase system (PTS) in osmotically shocked bacterial membrane vesicles. The soluble enzymes of the system were found to be in association with the membrane by several criteria. Phosphoenolpyruvate‐dependent sugar phosphorylation was catalyzed by this membrane‐bound enzyme system far more efficiently than by a mixture of the individual enzymes at corresponding concentrations. By contrast, the rates of the phosphoryl exchange reactions catalyzed by enzyme I and the enzyme II complexes were essentially the same for the associated and dissociated forms of the system. Functional association of the PTS‐enzyme complex was stabilized by Mg ++ and phosphoenolpyruvate and could be destroyed by detergent treatment, sonication, or by passage of the vesicle preparation through a French pressure cell. These results lead to the possibility that in the intact bacterial cell the soluble enzymes of the phosphotransferase system exist, in part, as peripheral membrane constituents associated with the integral membrane enzyme II complexes.