Further characterization of the acidic GPI-hydrolyzing phospholipase present in human sera.
A phospholipase from human serum capable of hydrolyzing glycosylphosphatidylinositol membrane anchors was described and partially characterized by our group some years ago. This activity presented a pH optimum between 5.0 and 6.0 and was inhibited by EDTA, EGTA and 1,10-phenanthroline. Partial purification showed that the enzyme was a glycoprotein with an apparent molecular weight of 140 kDa as judged by gel filtration. Other investigators characterized at the same time a phospholipase D with similar properties but with a pH optimum near 7.5. We now confirm that the human serum enzyme is indeed a phospholipase D capable of hydrolyzing mfVSG and glycolipids A and C from T. brucei. Isoelectric focusing of whole sera suggests the presence of two isoforms, one with a pI of 4.7 which was the form previously purified by our group, and others with pI from 6.2 to 7.4.
Stambuk
B U
BU
Departamento de Microbiologia, Imunologia e Parasitologia, Escola Paulista de Medicina, São Paulo, Brasil.
Cardoso-de-Almeida
M L
ML
D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007525:Isoelectric Focusing; D008049:Lipase / Q000097:blood / Q000378:metabolism*; D010739:Phospholipase D / Q000097:blood*; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000378:metabolism*
D017261:Glycosylphosphatidylinositols; D014643:Variant Surface Glycoproteins, Trypanosoma; D008049:Lipase; D010739:Phospholipase D