Solubilization of a high affinity Ca-ATPase from dog antrum smooth muscle

Abstract

A Mg-independent high affinity Ca-ATPase has recently been reported to be present in the plasma membranes of smooth muscle. This enzyme has now been solubilized using deoxycholate. The membrane-bound and the solubilized enzymes resemble each other in K m for Ca 2+, and inhibition by fluphenazine. The solubilized enzyme is, however, more sensitive to inhibition by Mg 2+ than the membrane bound enzyme. Radiation inactivation analysis shows that whereas the membrane-bound enzyme had a target size of 98,000 ± 4,000 Daltons, the solubilized enzyme was only 70,000, ± 7,000 Daltons.