Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Trypanosomatid protozoa are parasites of considerable medical and economic importance in developing countries. The pathway leading to N-glycosylation in these microorganisms is characterized by the following features: (i) dolichols are composed of only 10-13 isoprene units; (ii) oligosaccharides transferred in N-glycosylation have the compositions Man(6,7,9)GlcNAc2, depending on the species; (iii) trypanosomatids are unable to synthesize dolichol-P-Glc and, in addition, some species lack certain dolichol-P-Man-dependent mannosyltransferases; (iv) the oligosaccharyltransferase does not require the presence of glucose units in the oligosaccharide in order to catalyse an efficient transfer reaction; (v) trypanosomatids have a glucosidase II-like enzyme, but lack glucosidase I; (vi) glucosidase II is required for deglucosylation of oligosaccharides glucosylated by the UDP-Glc:glycoprotein glucosyltransferase, an activity first detected in those parasites; (vii) the structures of polymannose-type compounds in these protozoa have no significant differences with those of their mammalian counterparts except for the presence, in certain species, of oligosaccharides having galactofuranose units linked to external mannose residues; (viii) biantennary complex-type oligosaccharides having in some cases terminal alpha-linked galactose units or poly-N-acetylactosamine extensions, but lacking sialic acid units, have been described in Trypanosoma brucei; (ix) complex-type oligosaccharides having alpha-linked galactose, fucose and sialic acid residues have been described in Trypanosoma cruzi. In this parasite, addition of sialic acid units to glycoproteins and glycolipids is mediated by a trans-sialidase located on the external surface of the parasite and not by an intracellular CMP-sialic acid-dependent sialyltransferase.
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PMID:N-glycosylation in trypanosomatid protozoa. 835 46

Clostridium perfringens phospholipase C (Cp-PLC), also called alpha-toxin, is the major virulence factor in the pathogenesis of gas gangrene. Previously, a cellular UDP-Glc deficiency was related with a hypersensitivity to the cytotoxic effect of Cp-PLC. Because UDP-Glc is required in the synthesis of proteoglycans, N-linked glycoproteins, and glycosphingolipids, the role of these gly-coconjugates in the cellular sensitivity to Cp-PLC was studied. The cellular sensitivity to Cp-PLC was significantly enhanced by glycosphingolipid synthesis inhibitors, and a mutant cell line deficient in gangliosides was found to be hypersensitive to Cp-PLC. Gangliosides protected hypersensitive cells from the cytotoxic effect of Cp-PLC and prevented its membrane-disrupting effect on artificial membranes. Removal of sialic acids by C. perfringens sialidase increases the sensitivity of cultured cells to Cp-PLC and intramuscular co-injection of C. perfringens sialidase, and Cp-PLC in mice potentiates the myotoxic effect of the latter. This work demonstrated that a reduction in gangliosides renders cells more susceptible to the membrane damage caused by Cp-PLC and revealed a previously unrecognized synergism between Cp-PLC and C. perfringens sialidase, providing new insights toward understanding the pathogenesis of clostridial myonecrosis.
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PMID:A cellular deficiency of gangliosides causes hypersensitivity to Clostridium perfringens phospholipase C. 1591 67