Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study identifies and partially characterizes an insulin-sensitive glycophospholipid in H35 hepatoma cells. The incorporation of [3H]glucosamine into cell lipids was investigated. A major labeled lipid was purified by sequential thin layer chromatography using first an acid followed by a basic solvent system. After hydrochloric acid hydrolysis and sugar analysis by thin layer chromatography, 80% of the radioactivity in the purified lipid was found to comigrate with glucosamine. H35 cells were prelabeled with [3H]glucosamine for either 4 or 24 h and treated with insulin causing a dose-dependent stimulation of turnover of the glycophospholipid which was detected within 1 min. The purified glycolipid was cleaved by nitrous acid deamination indicating that the glucosamine C-1 was linked to the lipid moiety through a glycosidic bond. [14C]Ethanolamine, [3H]inositol, and [3H]sorbitol were not incorporated into the purified glycolipid. The incorporation of various fatty acids into this glycolipid was also studied. [3H]Palmitate was found to be preferentially incorporated while myristic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid were either not incorporated or incorporated less than 10% of palmitate. The purified glycolipid labeled with [3H]palmitate was cleaved by treatment with phospholipase A2 but was resistant to mild alkali hydrolysis suggesting the presence of a 1-hexadecyl,2-palmitoyl-glyceryl moiety in the purified lipid. Treatment of labeled glycophospholipid with phosphatidylinositol-specific phospholipase C from Staphylococcus aureus generated a compound migrating as 1-alkyl,2-acyl-glycerol and a polar head group with a size in the range from 800 to 3500. These findings coupled with the nitrous acid deamination demonstrate that glucosamine was covalently linked through a phosphodiester bond to the glyceryl moiety of the purified glycolipid. These findings suggest that insulin acts on this glycophospholipid by stimulating an insulin-sensitive phospholipase C. This unique glycophospholipid may play an important role in insulin action by serving as precursor of insulin-generated mediators.
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PMID:Identification of a novel insulin-sensitive glycophospholipid from H35 hepatoma cells. 354 86

The lipid moiety of the lipophosphoglycan of Leishmania donovani had been isolated and characterized as a novel lyso-alkylphosphatidylinositol. Treatment of lipophosphoglycan with either 10% NH4OH or a phosphatidylinositol-specific phospholipase C from Staphylococcus aureus liberated a monoalkylglycerol substituent. Structural characterization of the monoalkylglycerol by gas-liquid chromatography-mass spectrometry indicated the presence of two saturated, unbranched hydrocarbons: a C24 alkyl chain comprising 78% of the lipid with the remaining 22% as a C26 alkyl chain. Periodate sensitivity demonstrated that the alkyl side chain is linked to the C-1 position of the glycerol backbone. Treatment of lipophosphoglycan with nitrous acid released 1-O-alkylglycerophosphorylinositol due to an unacetylated glucosamine residue linked to the inositol of the lyso-alkylphosphatidylinositol. Quantitative analysis of the organic solvent-soluble product of nitrous acid deamination of lipophosphoglycan confirmed the expected ratio of inositol:phosphate:1-O-alkylglycerol as 1:1:1. These results suggest that L. donovani anchors its lipophosphoglycan with a unique lipid component.
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PMID:Structure of the lipid moiety of the Leishmania donovani lipophosphoglycan. 361 Oct 65

The major source of rat serum alkaline phosphatase (ALP) is well known to be from the intestinal enzyme, but it is still unclear whether it is from the duodenal or the ileal enzyme. The organic origin was investigated by means of two-dimensional electrophoresis. Major isoelectric points and molecular masses for activities of duodenal enzyme treated with both phosphatidylinositol-specific phospholipase C and neuraminidase were identified apparently with those of the major serum enzyme. In organ culture, the normal duodenal enzyme was released in the highest amounts to the culture medium. These results indicate that the major source of serum ALP in adult rats is basically from the duodenal enzyme. On the other hand, lectin affinity chromatography for ALPs showed that the ALP in the medium from culture duodenum and liver had the same complex-type sugar chain as with the ALP in the duodenal tissue. Although the duodenal ALP induced by glucosamine in vitro had the hybrid-type chain, sugar chains of the induced ALP in the culture medium were of the complex type, indicating that medial ALPs possessing the same sugar chain as the native duodenal enzyme, complex type, are mainly released from their tissues in normal conditions.
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PMID:Blood appearance of rat alkaline phosphatase originating from the duodenum in vitro. 369 1

The COOH terminus of the externally disposed variant surface glycoprotein (VSG) of the eukaryotic pathogenic protozoan Trypanosoma brucei strain 427 variant MITat 1.4 (117) is covalently linked to a novel phosphatidylinositol-containing glycolipid. This conclusion is supported by analysis of the products of nitrous acid deamination or Staphylococcus aureus phosphatidylinositol-specific phospholipase C treatment of purified membrane-form VSG. Lysis of trypanosomes is accompanied by release of soluble VSG, catalyzed by activation of an endogenous phospholipase C. The only apparent difference between membrane-form VSG and soluble VSG is the removal of sn-1,2-dimyristylglycerol. The COOH-terminal glycopeptide derived by Pronase digestion of soluble VSG was characterized by chemical modification and digestion with alkaline phosphatase. The results are consistent with the single non-N-acetylated glucosamine residue being the reducing terminus of the oligosaccharide and in a glycosidic linkage to a myo-inositol monophosphate that is probably myo-inositol 1,2-cyclic monophosphate. A partial structure for the VSG COOH-terminal moiety is presented. This structure represents a new type of eukaryotic post-translational protein modification and membrane anchor. We discuss the relevance of this structure to observations that have been made with other eukaryotic membrane proteins.
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PMID:Glycosyl-sn-1,2-dimyristylphosphatidylinositol is covalently linked to Trypanosoma brucei variant surface glycoprotein. 405 88

1. The lipids of Bacillus megaterium were extracted and three lipids containing glucosamine were identified. One of these is not a phospholipid, but the other two, which differ in their chromatographic behaviour, contain phosphorus, glycerol, fatty acid and d-glucosamine in the molar proportions 1:2:2:1. 2. In both phosphoglycolipids, the fatty acids are bound in ester linkage, and both yield 2,5-anhydromannose and 3-sn-phosphatidyl-1'-sn-glycerol on treatment with sodium nitrite. 3. Both phosphoglycolipids were N-acetylated and, after removal of fatty acids by mild alkaline hydrolysis, in both cases N-acetylglucosamine was quantitatively released by beta-N-acetylhexosaminidase. 4. The glucosaminylglycerols derived from the two phosphoglycolipids by partial acid hydrolysis differ in their behaviour towards periodate. In one case 1 mole of periodate is rapidly consumed/mole of glucosaminylglycerol, but in the other case under identical conditions the consumption of periodate is negligible. 5. The phosphoglycolipids were identified as 1'-(1,2-diacyl-sn-glycero-3-phosphoryl)-3'-O-beta-(2-amino-2-deoxy-d-glucopyranosyl)-sn-glycerol and as 1'-(1,2-diacyl-sn-glycero-3-phosphoryl)-2'-O-beta-(2-amino-2-deoxy-d-glucopyranosyl)-sn-glycerol. 6. Both phosphoglycolipids are good substrates for phospholipase A: neither is a substrate for phospholipase C from Clostridium perfringens, and only the 3'-glucosaminide is a substrate for phospholipase D.
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PMID:Isomers of glucosaminylphospatiylglycerol in Bacillus megaterium. 430 9

Giant-cell formation induced by macrophage fusion factor (MFF) was not altered after pretreatment of macrophages with trypsin, chymotrypsin, pronase, neuraminidase, phospholipase C, or phospholipase D. Pretreatment of macrophages with either alpha-mannosidase or alpha-glucosidase completely inhibited giant-cell development, without altering macrophage viability. No alteration of giant-cell formation was observed when 0.1 M of L-fucose, N-acetyl-glucosamine, D-arabinose, D-xylose, melibiose, D-glucose, D-galactose, alpha-lactose, sucrose, D-fructose, or maltose was present during incubation of macrophages with MFF. Giant-cell formation was abolished when 0.1 M alpha-D-mannose was present during macrophage incubation with MFF. These results suggest that the protein moiety of MFF recognizes a specific receptor site on the macrophage membrane, one that is different from those described for other lymphokines and contains alpha-mannose.
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PMID:Chemical nature of the interaction between macrophage fusion factor and macrophage membranes. 635 71

Intrinsic membrane proteins of rabbit red blood cells were labeled with the photoreactive amphipatic reagent 12-(4-azido-2-nitrophenoxy) stearoyl (1-14C) glucosamine, which inserts into the hydrophobic membrane region and generates a reactive nitrene upon ultraviolet irradiation. Photolabeling of membrane-bound staphylococcal alpha-toxin after lysis of probe-treated rabbit red blood cells by this toxin implies its penetration into the hydrophobic region of the outer leaflet of the membrane. In contrast clostridial theta-toxin and staphylococcal delta-toxin were not labeled, but extraction of intrinsic membrane proteins by delta-toxin was evidenced.
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PMID:Photolabeling of staphylococcal alpha-toxin from within rabbit erythrocyte membranes. 683 69

We have used suramin and brefeldin A to investigate the nature of a heparan sulphate proteoglycan that appears to recycle from the cell surface to intracellular compartments which synthesize new heparan sulphate chains. Suramin, which would block internalization and deglycanation of a putative recycling cell surface proteoglycan, markedly increases the yield of a membrane-bound proteoglycan with a core protein of 60-70 kDa and unusually long heparan sulphate side chains. When transport of newly made core proteins to their Golgi sites for glycosaminoglycan assembly is blocked, by using brefeldin A, [3H]glucosamine and [35S]sulphate incorporation into cell surface-bound heparan sulphate proteoglycan can still take place. After chemical biotinylation of cell surface proteins in brefeldin A-treated cells, followed by metabolic [35S]sulphation in the presence of the same drug, biotin-tagged [35S]proteoglycan can be demonstrated, indicating the presence of recycling proteoglycan species. By pre-labelling cells with [3H]leucine or [3H]inositol in the presence of suramin, followed by chase labelling with [35S]sulphate in the presence of brefeldin A, a 3H- and 35S-labelled, hydrophobic heparan sulphate proteoglycan with a core protein of 60-65 kDa is obtained. The proteoglycan loses its hydrophobicity when glucosamine-inositol bonds are cleaved, indicating that it is membrane bound via a glycosylphosphatidylinositol anchor. However, treatment with phosphatidylinositol-specific phospholipase C has no effect, suggesting that the inositol moiety may be acylated. We propose that a portion of the lipid-anchored proteoglycan glypican is internalized, recycled via the Golgi, where heparan sulphate chains are added, and finally re-deposited at the cell surface.
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PMID:Recycling of a glycosylphosphatidylinositol-anchored heparan sulphate proteoglycan (glypican) in skin fibroblasts. 757 95

Metabolic labelling experiments performed with cultured pituitary lactotrophes revealed the presence of a glycosyl-phosphatidylinositol (GPtdIns) structurally related to GPtdIns lipids isolated from other cell types as demonstrated by: (i) metabolic incorporation of [3H]galactose, [3H]glucosamine and [3H]inositol into the polar inositolphosphoglycan moiety (InsPG) and [3H]myristate and [3H]palmitate into the diacylglycerol (DAG) backbone of GPtdIns; (ii) sensitivity of the [3H]labelled GPtdIns to nitrous acid deamination and; (iii) sensitivity of GPtdIns to phosphatidylinositol (PtdIns)-specific phospholipase C (PLC) hydrolysis. In cultured pituitary cells labelled to isotopic steady state with 10 microCi/ml of [3H]glucosamine, treatment with hypothalamic TRH (10(-6) M) induced a rapid and transient hydrolysis (ca. 50%) of the labelled GPtdIns. Moreover, as demonstrated in [3H]inositol labelled cells, treatment with thyrotropin releasing hormone (TRH) elicited the cleavage of [3H]GPtdIns in a similar manner, and this effect was followed by the phosphoinositide (PtdIns, PtdInsP and PtdInsP2) hydrolysis 30 s later. These results suggest that the phosphodiesterase cleavage of GPtdIns could be an early event implicated in TRH action in pituitary lactotrophes.
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PMID:Partial characterization of a thyrotropin releasing hormone-sensitive glycosyl-phosphatidylinositol in pituitary lactotrophes. 761 97

The synthesis of sulfogalactosylglycerolipid (SGG) is a differentiation marker in spermatogenesis restricted to the zygotene and early pachytene spermatocytes. The galactolipid sulfotransferase responsible for the synthesis of SGG is regulated by a phosphorylation mechanism. The activity of this enzyme is reduced in cells later in spermatogenesis by a low molecular weight inhibitor, which can be extracted in organic solvents and purified by reverse phase high pressure liquid chromatography (HPLC). This purified inhibitor is a potent postreceptor insulin-mimetic, which stimulates adipocyte lipogenesis more effectively than does insulin. Phosphoinositol (PI) glycolipids have been proposed as second messengers of the insulin phosphorylation cascade. These species contain a nonacetylated glucosamine, which renders them liable to cleavage by deamidation. The activity of the sulfotransferase inhibitor was lost following nitrous acid deamidation and was labile to PI specific phospholipase C digestion. Insulin and insulin-like growth factor I were found to inhibit germ cell synthesis of SGG in vitro to some degree but had no direct effect on the testicular galactolipid sulfotransferase assay. These results indicate that the sulfotransferase inhibitor is a glycosyl phosphoinositide similar to the lipid species, which mediate insulin signal transduction and suggest that germ cell SGG biosynthesis may be regulated by a receptor-mediated phosphorylation pathway.
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PMID:Developmentally regulated testicular galactolipid sulfotransferase inhibitor is a phosphoinositol glycerolipid and insulin-mimetic. 801 31


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