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)

The main electric organ of Electrophorus electricus is particularly rich in thiamine triphosphate, which represents 87% of the total thiamine content in this tissue. The thiamine pyrophosphate concentration, however, is very low in the eel electric organ and skeletal muscle as compared with other eel or rat tissues. Furthermore, electroplax membranes contain a whole set of enzymes responsible for the dephosphorylation of thiamine tri-, pyro- and monophosphate. Thiamine triphosphatase has a pH optimum of 6.8 and is dependent on Mg2+. The real substrate of the enzyme is probably a 1:1 complex of Mg2+ and thiamine triphosphate. Thiamine pyrophosphatase is activated by Ca2+. The apparent Km for thiamine triphosphate and Vmax are found to be, respectively, 1.76 mM and 5.95 nmol/mg of protein/min. Thiamine triphosphatase activity is inhibited at physiological K+ concentrations (up to 90 mM) and increasing Na+ concentrations (50% inhibition at 300 mM). ZnCl2 (10 mM) inhibits 90% of the enzyme activity. ATP and ITP are also strongly inhibitory. No significant effect of neurotoxins is seen. Membrane-associated thiamine triphosphatase is affected differently by proteolytic enzymes and is partially inactivated by pretreatment with phospholipase C and neuraminidase. The physiological significance of thiamine triphosphatase is discussed in relation to a specific role of thiamine in the nervous system.
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PMID:Thiamine triphosphate and membrane-associated thiamine phosphatases in the electric organ of Electrophorus electricus. 303 30

The release of the Tritrichomonas foetus plasma-membrane ectoenzyme neuraminidase by exogenous specific phospholipase C (PI-PLC) was investigated. Neuraminidase activity was determined using both the peanut agglutinin (PNA) hemagglutination test and the specific substrate N-acetylneuramin-lactose in a colorimetric assay. The release of the neuraminidase by PI-PLC was dependent on the reaction time and the concentration of PI-PLC. Neuraminidase activity was also detected in supernatant of untreated T. foetus. Spontaneous or PI-PLC-induced release of neuraminidase from protozoan cells was markedly decreased by 10 mM ZnCl2, suggesting the occurrence of an endogenous PI-PLC in the parasite. After T. foetus lysis at 37 degrees C with a solution of Triton X-114, neuraminidase activity was preferentially found in the aqueous phase rather than in the detergent phase, again suggesting that the parasite contains an endogenous PI-PLC that converts the hydrophobic form of neuraminidase anchored to the T. foetus cell membrane into a hydrophilic form. These results show that neuraminidase is linked to the T. foetus plasma membrane via a glycosylphosphatidylinositol anchor.
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PMID:Phospholipase C-mediated release of neuraminidase from Tritrichomonas foetus cell surface. 777 Apr 23

While searching for a phospholipase C (PLC) specific for phosphatidylcholine in mammalian tissues, we came across such an activity originating from a contamination of Pseudomonas fluorescens. This psychrophilic bacterium was found to contaminate placental extracts upon processing in the cold. The secreted phosphatidylcholine-hydrolyzing PLC was purified by a combination of chromatographic procedures. As substrates, the enzyme preferred dipalmitoyl-phosphatidylcholine and 1-palmitoyl-2-arachidonoyl-phosphatidylcholine over phosphatidylinositol. The active enzyme is a monomer of approximately 40 kDa. As for other bacterial PLCs, the enzyme requires Ca2+ and Zn2+ for activity; dithiothreitol affected the activity due to its chelation of Zn2+, but this inhibition could be compensated for by addition of ZnCl2. The compound D609, described to selectively inhibit phosphatidylcholine-specific PLCs, caused half-inhibition of the P. fluorescens enzyme at approximately 420 microM, while 50-fold lower concentrations similarly affected PLCs from Bacillus cereus and Clostridium perfringens. Partial peptide sequences obtained from the pure P. fluorescens enzyme after tryptic cleavage were used to clone a DNA fragment of 3.5 kb from a P. fluorescens gene library prepared from our laboratory isolate. It contains an ORF of 1155 nucleotides encoding the PLC. There is no significant sequence homology to other PLCs, suggesting that the P. fluorescens enzyme represents a distinct subclass of bacterial PLCs. The protein lacks cysteine residues and consequently contains no disulfide bonds. Interestingly, P. fluorescens reference strain DSMZ 50090 is devoid of the PLC activity described here as well as of the relevant coding sequence.
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PMID:Molecular characterization of a phosphatidylcholine-hydrolyzing phospholipase C. 1158 99