Cadmium ion is a non-competitive inhibitor of red cell Ca(2+)-ATPase activity.
In the presence as well as in the absence of calmodulin, Cd2+ inhibits the human erythrocyte plasma membrane Ca(2+)-ATPase activity non-competitively with Ki = 2 nM, whereas ATP-dependent Ca(2+)-transport across the red cell membrane was found to be inhibited competitively by Cd2+ (Verbost, P.M., Flik, G., Pang, P.K.T., Lock, R.A.C. and Wendelaar Bonga, S.E. (1989) J. Biol. Chem. 264, 5613-5615). In this study it will be argued that Cd2+ also inhibits Ca(2+)-transport non-competitively, and that the discrepancy with previous conclusions most probably relies on use of an incorrect computer program that calculates the free concentrations of Ca2+ and Cd2+ at the experimental conditions applied for measurement of Ca2+ uptake.
Visser
G J
GJ
Laboratory of Cell Biology, University of Nijmegen, Faculty of Science, The Netherlands.
Peters
P H
PH
Theuvenet
A P
AP
D002104:Cadmium / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002147:Calmodulin; D004910:Erythrocyte Membrane / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008433:Mathematics; D012984:Software
D002147:Calmodulin; D002104:Cadmium; D000252:Calcium-Transporting ATPases