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)

A 150-kDa phospholipase C has previously been purified from turkey erythrocytes and has been shown by reconstitution with turkey erythrocyte membranes to be a receptor- and G-protein-regulated enzyme (Morris, A. J., Waldo, G. L., Downes, C.P., and Harden, T. K. (1990) J. Biol. Chem. 265, 13501-13507; Morris, A.J., Waldo, G.L., Downes, C.P., and Harden, T.K. (1990) J. Biol. Chem. 265, 13508-13514). Combination of this 150-kDa protein with phosphoinositide substrate-containing phospholipid vesicles prepared with a cholate extract from purified turkey erythrocyte plasma membranes resulted in conferrence of AlF4- sensitivity to the purified phospholipase C. Guanosine 5'-3-O-(thio)triphosphate also activated the reconstituted phospholipase C in a manner that was inhibited by guanosine 5'-2-O-(thio)-diphosphate. The magnitude of the AlF4- stimulation was increased with increasing amounts of plasma membrane extract, and was also dependent on the concentration of purified phospholipase C. Using reconstitution of AlF4- sensitivity as an assay, the putative G-protein conferring regulation to the 150-kDa phospholipase C was purified to near homogeneity by sequential chromatography over Q-Sepharose, Sephacryl S-300, octyl-Sepharose, hydroxylapatite, and Mono-Q. Reconstituting activity co-purified with an approximately 43-kDa protein identified by silver staining; lesser amounts of a 35-kDa protein was present in the final purified fractions, as was a minor 40-kDa protein. The 43-kDa protein strongly reacted with antiserum against a 12-amino acid sequence found at the carboxyl terminus of Gq and G11, the 35-kDa protein strongly reacted with G-protein beta-subunit antiserum, and the 40-kDa protein reacted with antiserum that recognizes Gi3. Immunoprecipitation of the 43-kDa protein resulted in loss of phospholipase C-stimulating activity of the purified fraction. The idea that this is a phospholipase C-regulating G-protein is further supported by the observation that co-reconstitution of G-protein beta gamma-subunit with the purified phospholipase C-activating fraction resulted in a beta gamma-subunit-dependent inhibition of AlF(4-)-stimulated phospholipase C activity in the reconstituted preparation.
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PMID:Purification of an AlF4- and G-protein beta gamma-subunit-regulated phospholipase C-activating protein. 165 Mar 51

A 150-kDa phospholipase C previously was purified from turkey erythrocytes and shown to be a P2Y-purinergic receptor- and guanine nucleotide-binding protein-regulated enzyme [J. Biol. Chem. 265:13508-13514 (1990)]. The relationship of this enzyme to the 150-kDa mammalian phospholipase C isoenzymes, termed phospholipase C-beta and -gamma, has been examined. Four antisera to the turkey erythrocyte phospholipase C recognized the avian enzyme in immunoblots but failed to recognize phospholipase C-gamma; one of the these weakly recognized phospholipase C-beta. Antibodies to phospholipase C-beta and -gamma failed to recognize the turkey erythrocyte phospholipase C. However, two antibodies raised against peptide sequence in regions of conserved sequence common to mammalian phospholipase C isoenzymes recognized the 150-kDa turkey erythrocyte phospholipase C. Antisera against the native form of the turkey erythrocyte phospholipase C inhibited the activity of this enzyme against phosphatidylinositol 4,5-bisphosphate presented as a component of mixed phospholipid vesicles or of mixed phospholipid and sodium cholate micelles; inhibition occurred as a decrease in Vmax, with no apparent change in Km for substrate or in the Ca2+ dependence of phospholipase C activity. Catalytic activity of phospholipase C-beta or -gamma against exogenous substrate was unaffected by antisera to the turkey erythrocyte enzyme. Antisera against the native form of the turkey erythrocyte phospholipase C also partially inhibited (50-60% inhibition) the capacity of AIF4- or adenosine 5'-O-(beta-thio) diphosphate plus guanosine 5'-O-(gamma-thio) triphosphate to stimulate phosphoinositide hydrolysis in ghosts prepared from [3H]inositol-prelabeled turkey erythrocytes. Moreover, the capacity of the purified 150-kDa enzyme to reconstitute receptor and G-protein-regulated phospholipase C activity in purified turkey erythrocyte plasma membranes devoid of this activity was completely inhibited by antisera to the turkey erythrocyte enzyme. Five peptides that were purified by high performance liquid chromatography from a tryptic digest of the turkey erythrocyte 150-kDa phospholipase C had no recognizable sequence homology with any deduced sequence of the mammalian phospholipase C isoenzymes. One turkey erythrocyte phospholipase C-derived peptide had clear homology with sequence in the first (X-domain) conserved region common to at least three of the mammalian phospholipase C isoenzymes, and another 16-amino acid peptide had partial sequence homology with the second (Y-domain) conserved region common to the mammalian enzymes. An 8-amino acid peptide from the tryptic digest had 75% homology with a sequence near the carboxyl terminus of mammalian phospholipase C-beta.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Receptor- and G-protein-regulated 150-kDa avian phospholipase C: inhibition of enzyme activity by isoenzyme-specific antisera and nonidentity with mammalian phospholipase C isoenzymes established by immunoreactivity and peptide sequence. 165 88