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

The effects of expression of the H-ras oncogene on phosphatidylcholine metabolism were examined in C3H10T1/2 and NIH3T3 cells expressing ras constitutively or under the control of inducible promoters. Cell lines expressing ras under the control of the mouse metallothionein promoter and the Escherichia coli lac operator/repressor system and an NIH3T3 cell line stably transfected with the ras oncogene were studied. Phosphocholine levels were elevated in the cells constitutively expressing ras and were increased 4-6 h upon induction in the inducible cell lines. Glycerophosphocholine, which is elevated five- to sixfold in constitutively transfected ras cells, did not increase at early times of induction, suggesting the absence of increased phosphatidylcholine degradation via a phospholipase A. Choline kinase activity increased within 4-6 h upon induction and correlated well with the increase in phosphocholine levels. This increase in phosphocholine levels could be prevented by the addition of hemicholinium-3, a competitive inhibitor of choline kinase. Expression of activated c-raf or v-raf also increased choline kinase activity, suggesting that the induction of choline kinase by ras is downstream of the ras/raf interaction. Long-term and short-term labeling experiments failed to detect evidence for increased phospholipase C activity. These results suggest that the increase in choline kinase activity observed in cells expressing ras is an early, integral part of ras transformation and is the main contributor to increased phosphocholine levels accompanying morphological changes.
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PMID:Early increase in choline kinase activity upon induction of the H-ras oncogene in mouse fibroblast cell lines. 748 93

We recently identified phospholipase activity as a potential virulence factor of Cryptococcus neoformans. We have now defined the nature of the phospholipase activity produced by a clinical isolate of C. neoformans var. neoformans, under native conditions, by 1H and 31P nuclear magnetic resonance (NMR) spectroscopy and thin-layer chromatography (TLC) of radiolabelled substrates. Glycerophosphocholine was identified by NMR spectroscopy as the sole phospholipid degradation product of the reaction between substrate phosphatidylcholine (PC) and cryptococcal culture supernatants indicating the presence of phospholipase B (PLB). No lysophosphatidylcholine (lyso-PC) or products indicative of phospholipase C, phospholipase D, or other lipase activity were identified. Use of PC and lyso-PC containing radiolabelled acyl chains and separation of products by TLC confirmed the PLB and lysophospholipase (LPL) activities. Lysophospholipase transacylase (LPTA) activity was identified by the formation of radioactive PC from lyso-PC. Extracellular enzyme production was maximal after 6 to 10 h in fresh medium. Assay conditions were optimized for pH, linearity with time, enzyme concentration, and saturation by substrates to allow comparison with phospholipases from other organisms. LPL activity was 10- to 20-fold greater than PLB activity, with mean (+/- standard deviation) specific activities of 34.9 +/- 7.9 and 3.18 +/- 0.2 micromol of substrate hydrolyzed per min per mg of protein, respectively. The response of PLB to increasing substrate concentrations was bimodal, whereas inhibition of LPL and LPTA activities occurred at concentrations of substrate lyso-PC greater than 200 microM. Enzyme activities were stable at acid pH (3.8), with pH optima of 3.5 to 4.5. Activities were unchanged in the presence of exogenous serine protease inhibitors, divalent cations, and EDTA. We conclude that C. neoformans produces highly active extracellular PLB, LPL, and LPTA under native conditions.
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PMID:Identification of extracellular phospholipase B, lysophospholipase, and acyltransferase produced by Cryptococcus neoformans. 900 89