Navegando por Palavras-chave "PHOSPHOLIPASE C"

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    CHARACTERIZATION OF A PHOSPHOLIPASE C-RESISTANT INOSITOL CONTAINING GLYCOLIPID FROM TRYPANOSOMA-CRUZI
    (Assoc Bras Divulg Cientifica, 1994-02-01) Heise, Norton [UNIFESP]; Raper, J.; Cardosodealmeida, M. L.; JOHNS HOPKINS UNIV; Universidade Federal de São Paulo (UNIFESP)
    Since glycosylphosphatidylinositol is the most common form of attachment of proteins to membranes in T. cruzi, and that this parasite depends on surface-mediated interactions for survival within the vector and mammalian host, it is probable that a drug which interfers with the metabolism of glycosylphosphatidylinositol (GPI) could be successfully employed in chemotherapy. Over the last few years several groups have been characterizing this mode of attachment in T. cruzi and more recently we have been concentrating our efforts on the identification of candidate precursors for protein anchors in metacyclic trypomastigotes. Previously detected GPI heterogeneity regarding solubilization of a major stage-specific antigen (1G7-Ag) by phospholipase C led us to investigate whether biosynthetic precursors with similar properties could also be identified. Two glycolipid species whose migration properties resemble glycolipids A and C of T. brucei were amenable to biosynthetic radiolabelling with palmitic acid, inositol, ethanolamine, glucosamine and mannose. Following purification,these species were submitted to classical GPI diagnostic treatments. In both cases digestion with GPI-specific phospholipase D (GPIPLD) produced phospatidic acid and treatment with either mild base or phospholipase A(2) (PLA(2)) produced free fatty acid, indicating an acylation at least at position 2 of the glycerol. The glycolipid A-like species proved to be susceptible to solubilization by PIPLC of B. thuringiensis and by GPIPLC of T. brucei and the glycolipid C-like material proved to be fully resistant to both lipases. Although the glycolipid A-like species indeed presents these and other properties compatible with a precursor for the chemically characterized 1 G7-Ag anchor, the PLC-resistant species which is completely insensitive to nitrous acid deamination might be an exception to the general finding of a non-acetylated glucosamine in the GPI moieties so far described.
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    PARACOCCIDIOIDES-BRASILIENSIS EXPRESSES BOTH GLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED PROTEINS and A POTENT PHOSPHOLIPASE-C
    (Academic Press Inc Jnl-comp Subscriptions, 1995-06-01) Heise, N.; Travassos, L. R.; Dealmeida, MLC; Universidade Federal de São Paulo (UNIFESP)
    This study reports, for the first time, the detection of glycosylphosphatidylinositol (GPI) membrane anchors in proteins of a pathogenic fungus, Paracoccidioides brasiliensis. Taking into account that fungal antigens are found in the sera of paracoccidioidiomycosis patients and that cleavage of this glycolipid by phospholipases is a means of selective protein release, the presence of an enzyme with this property has also been investigated Using a methodological approach in which the proteins were immobilized on nitrocellulose, treated with phospholipase C of Trypanosoma brucei and then probed with antibodies which recognize the 1,2-cyclic-phosphate inositol moiety formed as a reaction product in proteins bearing the glycolipid anchor, it was possible to detect a major glycoprotein in the 80- to 90-kDa range, as well as two other minor species of 66 and 43 kDa. All of them bind to Concanavalin-A and are also substrates of a very potent fungal phospholipase C which is inhibited by p-chloromercuri-phenylsulfonic acid and is insensitive to EDTA. the integrity of glycosylphosphatidylinositol anchors in proteins of P. brasiliensis is impaired by 0.1 M NaOH, a finding indicative of a diacyl glycerolipid moiety which is quite surprising since it is, with the exception of African trypanosomes surface proteins and Torpedo acetylcholinesterase, an uncommon feature among GPIs in general. the present findings may have implications in the pathology of paracoccidiodomycosis. (C) 1995 Academic Press, Inc.