THE C-TERMINUS OF GLYCOSYLPHOSPHATIDYLINOSITOL-SPECIFIC PHOSPHOLIPASE-D IS ESSENTIAL FOR BIOLOGICAL-ACTIVITY

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) (EC 3. 1.4.50) from mammalian serum is a 115 kDa glycoprotein consisting of 8 16 amino acids. We found that C-terminal deletions of only two to five amino acids reduced GPI-PLD enzymatic activity by roughly 70% as comp ared to wild-type protein. C-terminal deletions of more than five amin o acids resulted in a complete loss of GPI-PLD enzymatic activity. Poi nt mutations at position 811 indicate that Tyr-811 may play a major ro le in maintaining the biological activity of GPI-PLD.