The Relation of Phosphate Metabolism to Oxidative Assimilation of Acetate by Euglena gracilis var. bacillaris. Effects of 2,4-Dinitrophenol*
Supported in part by Public Health Service Research Grant GM-07918 from the Division of General Medical Sciences, and by National Science Foundation Research Grant GB 15656. The results published here are taken from a thesis presented by Kenneth J. Collyard in partial fulfillment of the requirements for the M.S. degree at Illinois Institute of Technology.
Abstract
SYNOPSIS. Oxidative assimilation of acetate by Euglena gracilis var. bacillaris occurs without appreciable net transfer of inorganic phosphate between cells and medium. Low concentrations of the “uncoupling agent” 2,4-dinitrophenol (2–5 μM, pH 5) stimulate acetate oxidation and inhibit acetate assimilation. These dinitrophenol concentrations have no measurable effect on edogenous respiration. Higher concentrations inhibit respiration on acetate, and still higher concentrations inhibit endogenous respiration.
Dinitrophenol concentrations which stimulate acetate oxidation produce no measurable change in the total ATP content of the euglena cells. Higher concentrations (50–100 μM) cause progressive decrease in the ATP content.
A hypothetical mechanism is proposed which accounts for the normal, constant oxidation-assimilation ratio for acetate as the result of coupling of oxidative ATP synthesis with assimilatory ATP consumption. The data are consistent with this mechanism if it is additionally assumed that oxidation and assimilation of acetate occur in an intracellular “compartment” separated from other sources and sinks of ATP.
