Ectoenzymes of the kidney microvillar membrane Aminopeptidase P is anchored by a glycosyl‐phosphatidylinositol moiety

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Abstract
The mode of membrane anchorage of three kidney microvillar membrane ectoenzymes has been examined. The release of aminopeptidase P (EC 3.4.11.9) from kidney membranes by bacterial phosphatidylinositol‐specific phospholipase C (PI‐PLC) and the pattern of detergent solubilization of this ectoenzyme implies that it is anchored to the membrane via a covalently attached glycosyl‐phosphatidylinositol moiety. As deduced by phase separation in Triton X‐114, octyl‐glucoside solubilized the amphipathic form of aminopeptidase P, whereas the PI‐PLC‐released form displayed hydrophilic properties. In contrast, the pattern of detergent solubilization of two microvillar carboxypeptidases and their resistance to release from the membrane by bacterial PI‐PLC suggest that these two ectoenzymes are not anchored via phosphatidylinositol.