Decreased red cell enolase activity in a 40-year-old woman with compensated haemolysis.

A 40-year-old woman splenectomized 17 years previously for hereditary haemolytic anaemia was investigated in our laboratory because of persistent conjunctival subicterus associated with compensated haemolysis. The results of the autohaemolysis and osmotic fragility tests were similar to those usually observed in hereditary spherocytosis. Red cell enzyme assays indicated a decreased amount of kinetically normal enolase. The genetic transmission of this defect could not be established since the only other affected member of the family was the proposita's father who died several years ago after splenectomy for an undefined haemolytic disorder.

Evidence for the involvement of (Cu-ATP)2- in the inhibition of human erythrocyte (Ca2+ + Mg2+)-ATPase by copper.

The effects of copper on the activity of erythrocyte (Ca2+ + Mg2+)-ATPase have been tested on membranes stripped of endogenous calmodulin or recombined with purified calmodulin. The interactions of copper with Ca2+, calmodulin and (Mg-ATP)2- were determined by kinetic studies. The most striking result is the potent competitive inhibition exerted by (Cu-ATP)2- against (Mg-ATP)2- (Ki = 2.8 microM), while free copper gives no characteristic inhibition. Our results also demonstrate that copper does not compete with calcium either on the enzyme or on calmodulin. The fixation of calmodulin on the enzyme is not altered in the presence of copper as shown by the fact that the dissociation constant remains unaffected. It may be speculated that (Cu-ATP)2- is the active form of copper, which could plausibly be at the origin of some of the pathological features of erythrocytes observed in conditions associated with excess copper.