Interaction of α‐1,2‐mannosidase with anionic phospholipids

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Abstract
A partially purified microsomal .alpha.-1,2-mannosidase from rabbit liver binds to vesicles that contain anionic phospholipids. The affinity of the enzyme for the phospholipid vesicles is dependent on the negative charge density of the vescles rather than the concentration of the anionic phospholipid or the phospholipid specificity. A phosphatidylinositol/phosphatidylcholine ratio of 1:3 is sufficient to bind all of the enzyme. The association of enzyme with anionic phospholipids involves ionic interactions and can be readily reversed by high ionic strength or changes in pH. The .alpha.-mannosidase in inhibited when bound to the anionic phospholipid vesicles, but the enzyme can be reactivated when released by NaCl or CaCl2. When bound to anionic phospholipid vesicles, the enzymes was also found to undergo a slow inactivation process that was time and temperature dependent and could not be reversed by the addition of CaCl2.