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Transport of lactate and acetate through the energized cytoplasmic membrane of Escherichia coli
Author(s) -
Axe Douglas D.,
Bailey James E.
Publication year - 1995
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260470103
Subject(s) - glycolysis , chemistry , anaerobic exercise , escherichia coli , chemiosmosis , membrane , cytoplasm , biophysics , lactic acid , anaerobic glycolysis , biochemistry , nuclear magnetic resonance spectroscopy , metabolism , bacteria , stereochemistry , atp synthase , biology , enzyme , genetics , physiology , gene
Escherichia coli produces lactate and acetate in significant amounts during both aerobic and anaerobic glycolysis. A model describing the mechanism of protein mediated lactate transport has previously bee proposed. A simple theoretical analysis here indicates that the proposed model would be drain cellular energy resources by catalytically dissipating the proton‐motive force. An experimental analysis of lactate and acetate transport employ nuclear magnetic resonance (NMR) spectroscopy to measure the relative concentration of these end products on the two sides of the cytoplasmic membrane of anaerobically glycolyzing cells. Comparison of measured concentration rations to those expected at equilibrium for various transport modes indicates that acetate is a classical uncoupling agent, permeating the membrane oat comparable rates in the dissociated and undissociated forms. The lactate concentration ratio changes market markedly after an initial period of sustained glycolysis. This change is most readily explained as resulting from a lactate transport system that responds to an indicator of glycolytic activity. The data further indicates that lactate permeates the membrane in both dissociated and undissociated forms. Both acids, then are capable of catalytically dissipating the proton‐motives force. © 1995 John Wiley & Sons, Inc.