Enzymatic release of Zn2+-glycerophosphocholine cholinephosphodiesterase from brain membranes by glycosylphosphatidylinositol-specific phospholipases and its regulation.
Enzymatic conversion of glycosylphosphatidylinositol (GPI)-linked Zn2+-glycerophosphocholine phosphodiesterase was investigated. The activity of glycosylphosphatidylinositol-specific phospholipase-D (GPI-PLD), based on the conversion of amphiphilic form of phosphodiesterase into hydrophilic form, showing an optimum pH of about pH 6.6, increased continuously until 60 min. The activity of membrane-bound GPI-PL, based on the formation of hydrophilic form of phosphodiesterase, exhibiting an optimum pH of 7.4, increased up to 30 min, and reached a plateau. Inhibition studies indicate that while GPI-PLD activity was generally sensitive to ionic bio-detergents, it was not inhibited by myristoyl glycerol, a neutral detergent. Meanwhile, the membrane-bound GPI-PL was not affected remarkably by these detergents except that myristoyl glycerol expressed a modest increase of activity of membrane bound GPI-PL. In addition, the membrane-bound GPI-PL appeared to be enhanced by by suramin or oleic acid, which strongly inhibited GPI-PLD. From this results, it is suggested that in brain there may be two phospholipases responsible for the conversion of membrane-bound GPI-anchors to hydrophilic forms, and that this conversion might be regulated by endogenous lipids.
Lee
J Y
JY
College of Pharmacy, Chungnam National University, Taejon, Korea.
Kim
M R
MR
Sok
D E
DE
D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000378:metabolism; D002417:Cattle; D003902:Detergents / Q000378:metabolism / Q000494:pharmacology; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008566:Membranes; D010739:Phospholipase D / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D012995:Solubility; D015032:Zinc / Q000378:metabolism*
D003902:Detergents; D017261:Glycosylphosphatidylinositols; D010740:Phospholipases; D010727:Phosphoric Diester Hydrolases; C061931:glycerophosphocholine cholinephosphodiesterase; D010739:Phospholipase D; C065017:glycoprotein phospholipase D; D015032:Zinc