Effects of triton X-100 and concanavalin A on the properties of 5'-nucleotidase in rat liver and adipose plasma membranes: a role of membrane structure in the regulation of enzyme activity.
The kinetic and thermodynamic properties of 5'-nucleotidase (EC 3.1,3.5) were investigated in rat liver and adipose plasma membranes (PM) after their structural modification with nonionic detergent Triton X-100 (TX-100) or lectin concanavalin A (Con-A). The apparent K(m) value of 5'-nucleotidase decreased after PM treatment with subsolubilizing TX-100 concentrations (0.005-0.015%) and then tended to grow at higher TX-100 concentrations (0.03-0.05%). Treatment of PM with Con-A resulted in the noncompetitive inhibition of 5'-nucleotidase in a dose-dependent manner. The Arrhenius plot of the 5'-nucleotidase activity in the control PM exhibited a single well defined break at about 28-31 degrees C with a lower activation energy at the upper slope of the graph. The shape of the Arrhenius graphs and the thermodynamic parameters of 5'-nucleotidase were specifically modified upon the PM treatment with increasing concentrations of TX-100 or Con-A. It was suggested that the functional activity of 5'-nucleotidase and its conformation within the membrane matrix may be directly regulated by the structural states of the enzyme specific microenvironment and of the membrane lipid bilayer. Moreover, the existence of the spatial and/or compositional optima for the relationship between the enzyme molecule and its lipid surrounding may be reasonably supposed.
Yegutkin
G G
GG
Institute of Radiobiology, Belarussian Academy of Sciences, Minsk.
D015720:5'-Nucleotidase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D017830:Octoxynol / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D003208:Concanavalin A; D017830:Octoxynol; D015720:5'-Nucleotidase