Midportion antibodies stimulate glycosylphosphatidylinositol-specific phospholipase D activity.
Limited information is known regarding the regulation, structural features, and functional domains of glycosylphosphatidylinositol-specific phospholipase D ( GPI- PLD, EC 3. 1.4.50). Previous studies demonstrated that trypsin cleavage of GPI- PLD at or near Arg325 and/or Arg589 in bovine serum GPI-PLD was associated with an increase in enzymatic activity. Since the Arg325 is predicted to be in a region between the catalytic domain and predicted beta-propeller structure in the C-terminal portion of GPI- PLD (T. A. Springer, Proc. Natl. Acad. Sci. USA 94, 65-72, 1997), we hypothesized that this connecting region is important for catalytic activity. Trypsin cleavage of human serum GPI- PLD, which has an Arg325 but lacks the Arg589 present in bovine serum GPI-PLD, also increased GPI- PLD activity. Peptide-specific antibodies to residues 275-296 (anti-GPI-PLD(275)) and a monoclonal antibody, 191, with an epitope encompassing Arg325, also stimulated GPI- PLD activity. Pretreating human GPI- PLD with trypsin demonstrated that anti-GPI-PLD(275) only stimulated the activity of intact GPI- PLD. These results suggest that trypsin activation and anti-GPI-PPLD(275) may have similar effects on GPI- PLD. Consistent with this is the observation that both manipulations decreased the affinity of GPI- PLD for mixed micelle substrates. These results indicate that the midportion region of GPI- PLD is important in regulating enzymatic activity.[1]References
- Midportion antibodies stimulate glycosylphosphatidylinositol-specific phospholipase D activity. Deeg, M.A., Bowen, R.F. Arch. Biochem. Biophys. (1999) [Pubmed]
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