| Abstrakt: |
Abstract  It is believed that the biological effects of chelating agents such as crown ethers are largely related to their ability to form complexes with ions and/or to facilitate ion transport across membranes. Specific influences are rarely related. Here we present the evidence that even one of the simplest representatives of the crown ether super-family, 1,4,7,10,13,16-hexaoxacyclooctane (18-crown-6), is able to affect the activity of Na, K+ATPase directly. Using nonlinear regression fitting to kinetic data we have found that the crown ether diminishes the apparent Michaelis constant, K m , and the maximal rate of ATP hydrolysis, V m , acting as noncompetitive inhibitors. The apparent dissociation constants, K i , for the crown interaction with the free ATPase and with the enzyme-substrate complex were established to be of 77 ± 3 mM and 21 ± 2 mM, respectively. So 18-crown-6 possesses weak but âdirectâ pharmacological activity on Na, K+ATPase hinders the formation of enzymeâsubstrate complex and detains the enzyme in this state. [ABSTRACT FROM AUTHOR] |
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