title: The effect of 2,4-dinitrophenol on steroid transport in membrane vesicles of Pseudomonas testosteroni.
abstract: Steroid transport in Pseudomonas testosteroni membrane vesicles was significantly inhibited by the uncoupled 2,4-dinitrophenol (DNP). Inhibition of steroid transport was not due to inhibition of the 3 beta- and 17 beta-hydroxysteroid dehydrogenase by concentrations of up to 1 mM DNP. However, inhibition of this membrane-bound enzyme was measured at 10 mM DNP. The solubilized 3 beta- and 17 beta-hydroxysteroid dehydrogenase was more sensitive, being inhibited at both 1 and 10 mM DNP indicating a specific inhibition of this enzyme by DNP. Testosterone-dependent oxygen consumption was stimulated slightly at low concentrations of DNP and inhibited at high concentrations. The inhibition of testosterone-dependent oxygen consumption correlated with the inhibition of transport. This indicated that the inhibition of transport by DNP was due to a direct inhibition of metabolism. The existence of an electrochemical gradient is used to explain these results.
mesh_terms: D019297:2,4-Dinitrophenol; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004140:Dinitrophenols / Q000494:pharmacology*; D007700:Kinetics; D011549:Pseudomonas / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism*
chemical_list: D004140:Dinitrophenols; D013739:Testosterone; D019297:2,4-Dinitrophenol