Effects of magnesium plus vanadate on partial reactions of the Ca(2+)-ATPase from human red cell membranes.
Under conditions in which pretreatment with Mg2+ plus vanadate activate the Ca(2+)-ATPase, the initial rate of phosphorylation of the enzyme increased from 141 to 259 pmol/mg protein per s while the steady-state level of phosphoenzyme lowered from 1.9 to 1.1 pmol/mg protein. The drop in phosphoenzyme level was caused by incubation and washing during treatment rather than by vanadate. The data allowed to estimate a turnover number for the enzyme that raised by 170% after pretreatment. The results show that the activation of the Ca(2+)-ATPase by Mg2+ plus vanadate is due to changes in the kinetic properties of the enzyme.
Romero
P J
PJ
Instituto de Biología Experimental, Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
Rega
A F
AF
D000252:Calcium-Transporting ATPases / Q000187:drug effects / Q000378:metabolism*; D004347:Drug Interactions; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010766:Phosphorylation; D014638:Vanadates / Q000494:pharmacology*
D014638:Vanadates; D000252:Calcium-Transporting ATPases; D008274:Magnesium