Kinetics of Cu2+ inhibition of Na+/K(+)-ATPase.
The interaction of Cu2+ with enzymatic activity of rabbit kidney Na+/K(+)-ATPase was studied in media with buffered, defined free Cu2+ levels. The IC50-values are 0.1 mumol/l for Na+/K(+)-ATPase and 1 mumol/l for K(+)-pNPPase. Dithiothreitol (DTT) reverses the inhibitory effect of Cu2+ in vitro. Cu2+ exerts non-competitive effects on the enzyme with respect to Na+, K+, ATP or pNPP, but has a mixed-type inhibitory effect with respect to Mg2+. It is concluded that the appreciation of the inhibitory effect of Cu2+ on this enzyme requires carefully composed assay media that include a buffer for Cu2+, and that the IC50-values calculated according to this model indicate that Cu2+ may be more toxic than previously anticipated.
Li
J
J
Department of Animal Physiology, Faculty of Science, Toernooiveld, Nijmegen, The Netherlands.
Lock
R A
RA
Klaren
P H
PH
Swarts
H G
HG
Schuurmans Stekhoven
F M
FM
Wendelaar Bonga
S E
SE
Flik
G
G
D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D003300:Copper / Q000494:pharmacology*; D004229:Dithiothreitol / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology; D008274:Magnesium / Q000032:analysis; D011817:Rabbits; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013379:Substrate Specificity
D003300:Copper; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D004229:Dithiothreitol