Possible Adsorption of Aldolase and Glyceraldehyde-3-Phosphate Dehydrogenase into the Erythrocyte Ghosts Prepared Under a Hypotonic Condition

Abstract

Detectable activities of aldolase and of glyceraldehyde phosphate dehydrogenase in human erythrocyte ghost could be varied considerably depending on the conditions of preparing the ghosts which affect adsorption of the enzymes to the membrane or which influence permeability of the membrane to the enzyme substrate. The ghosts prepared in hypotonic veronal buffer contain approximately half of the respective enzyme activity found in intact erythrocytes, which is sometimes not fully measured due to the membrane permeability barrier against the externally-added substrate. These enzyme activities in the membrane, however, could be eluted away by homogenizing the ghost in isotonic saline. The membrane fragments which had been prepared by direct homogenization of intact cells in isotonic saline or by homogenization of ghosts obtained by saponin hemolysis in isotonic medium, contained only a very small part of these enzymes. Therefore, it is suggested that these enzymes are originally not the membrane-bound enzymes but may be the ones artificially adsorbed from cytoplasmic fluid onto inner surface of the plasma membrane when ghosts are prepared under a hypotonic condition.