@entity4495 (GPI)-specific phospholipases are highly valuable for studying the structure and function of GPIs. GPI-specific phospholipase C (GPI-PLC) from @entity3177 and @entity4357 -specific phospholipase C (PI-PLC) from @entity5259 are the most widely studied of this class of phospholipases C. Inhibition of protein activity by @entity1432 reagents is indicative of the participation of @entity462 residues in biochemical events. The @entity1432 reagent @entity52313 ( @entity52313 ) inhibits @entity3177 GPI-PLC, which has eight @entity462 residues. Surprisingly, we found that the activity of @entity5259 PI-PLC is also blocked by pCMPS, although the protein does not contain @entity462 residues. Inhibition of @entity5259 PI-PLC was reversed when pCMPS was size-separated from a preformed pCMPS.PI-PLC complex. In contrast, no activity was recovered when @entity3177 GPI-PLC was subjected to a similar protocol. Equimolar @entity5643 (beta-ME) reversed the inhibition of PI-PLC activity in a pCMPS.PI-PLC complex. For @entity3177 GPI-PLC, however, ultrafiltration of the pCMPS.GI-PLC complex and addition of a large excess of beta-ME was necessary for partial recovery of enzyme activity. Thus @entity3177 GPI-PLC is susceptible to inactivation by covalent modification with pCMPS, whereas PI-PLC is not. Kinetic analysis indicated that pCMPS was a competitive inhibitor of PI-PLC when a GPI was a substrate. Curiously, with @entity4357 as substrate, inhibition was no longer competitive. These data suggest that pCMPS is a glyco-mimetic that occupies the glycan binding site of PI-PLC, from where, depending on the substrate, it inhibits catalysis allosterically or competitively.

XXXX -less @entity4495 -specific phospholipase C is inhibited competitively by a @entity1432 reagent: evidence for glyco-mimicry by @entity52313 .

@entity5643 :: ('CHEBI:41218', 'Chemical') :: ['beta-mercaptoethanol'] @entity52313 :: ('MESH:D002731', 'Chemical') :: ['pCMPS', 'p-chloromercuriphenylsulphonate'] @entity462 :: ('MESH:D003545', 'Chemical') :: ['cysteine'] @entity3177 :: ('5691', 'Species') :: ['Trypanosoma brucei', 'T. brucei'] @entity1432 :: ('CHEBI:29256', 'Chemical') :: ['thiol'] @entity5259 :: ('1396', 'Species') :: ['Bacillus cereus', 'B. cereus'] @entity4495 :: ('MESH:D017261', 'Chemical') :: ['Glycosylphosphatidylinositol'] @entity4357 :: ('MESH:D010716', 'Chemical') :: ['phosphatidylinositol']
@entity462 :: (MESH:D003545,Chemical) :: ['Cysteine']
