Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Aminopeptidase P that hydrolyzes the Arg1-Pro2-bond of bradykinin was solubilized from rat lung microsomes using phosphatidylinositol-specific phospholipase C. The enzyme was purified 420-fold by chromatography on decylagarose (two steps), omega-aminodecyl-agarose and DEAE-Sephacel. A single stained band was observed following native gradient (4-15%) polyacrylamide gel electrophoresis. Dipeptidylaminopeptidase IV-like activity was also present in the final preparation and co-migrated with aminopeptidase P in the above gel system.
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PMID:Aminopeptidase P: purification of a membrane-bound bradykininase from rat lung. 136

Many proteins of eukaryotic cells are anchored to membranes by covalent linkage to glycosyl-phosphatidylinositol (GPI). These proteins lack a transmembrane domain, have no cytoplasmic tail, and are, therefore, located exclusively on the extracellular side of the plasma membrane. GPI-anchored proteins form a diverse family of molecules that includes membrane-associated enzymes, adhesion molecules, activation antigens, differentiation markers, protozoan coat components, and other miscellaneous glycoproteins. In the kidney, several GPI-anchored proteins have been identified, including uromodulin (Tamm-Horsfall glycoprotein), carbonic anhydrase type IV, alkaline phosphatase, Thy-1, BP-3, aminopeptidase P, and dipeptidylpeptidase. GPI-anchored proteins can be released from membranes with specific phospholipases and can be recovered from the detergent-insoluble pellet after Triton X-114 treatment of membranes. All GPI-anchored proteins are initially synthesized with a transmembrane anchor, but after translocation across the membrane of the endoplasmic reticulum, the ecto-domain of the protein is cleaved and covalently linked to a preformed GPI anchor by a specific transamidase enzyme. Although it remains obscure why so many proteins are endowed with a GPI anchor, the presence of a GPI anchor does confer some functional characteristics to proteins: (1) it is a strong apical targeting signal in polarized epithelial cells; (2) GPI-anchored proteins do not cluster into clathrin-coated pits but instead are concentrated into specialized lipid domains in the membrane, including so-called smooth pinocytotic vesicles, or caveoli; (3) GPI-anchored proteins can act as activation antigens in the immune system; (4) when the GPI anchor is cleaved by PI-phospholipase C or PI-phospholipase D, second messengers for signal transduction may be generated; (5) the GPI anchor can modulate antigen presentation by major histocompatibility complex molecules. Finally, at least one human disease, paroxysmal nocturnal hemoglobinuria, is a result of defective GPI anchor addition to plasma membrane proteins.
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PMID:Glycosyl-phosphatidylinositol-anchored membrane proteins. 145 Mar 66

The membrane-bound form of aminopeptidase P (aminoacylprolyl-peptide hydrolase) (EC 3.4.11.9) was purified to apparent homogeneity from bovine lung microsomes. The enzyme was solubilized using phosphatidylinositol-specific phospholipase C (Bacillus thuringiensis), indicating that bovine lung amino-peptidase P is attached to membranes via a glycosylphosphatidylinositol anchor. The enzyme was purified 1900-fold with a yield of 25% by chromatography on decyl-agarose, omega-aminodecyl-agarose, a second decylagarose column, DEAE-Sephacel, and an ultrafiltration step. Native gradient polyacrylamide gel electrophoresis revealed a single stained protein band whose position in the gel corresponded to cleavage of the Arg1-Pro2 bond of bradykinin. The Mr was 360,000 by gel permeation chromatography and 95,000 by reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The substrate specificity of aminopeptidase P was determined using approximately 50 peptides with proline in the second position. The enzyme could hydrolyze lower NH2-terminal homologs of bradykinin, including Arg-Pro-Pro, which was used as the routine substrate in a rapid fluorescence assay performed in the absence of added Mn2+. Some peptides having NH2-terminal amino acids other than arginine were also cleaved. Aminopeptidase P appeared to favor peptides that had 2 proline residues or proline analogs in positions 2 and 3 of the substrate. In general, tripeptides having a single proline residue in position 2 were poor substrates. Aminopeptidase P was inhibited by a series of peptides, 3-8 residues long, having an NH2-terminal Pro-Pro sequence. The enzyme was also inhibited by metal-chelating agents, 2-mercaptoethanol (4 mM), p-chloromercuribenzenesulfonic acid, and NaCl at concentrations greater than or equal to 0.25 M. The purified enzyme had a pH optimum of 6.5-7.0 and was most stable in the basic pH range. A role for membrane-bound aminopeptidase P in the pulmonary inactivation of circulating bradykinin is proposed.
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PMID:Membrane-bound aminopeptidase P from bovine lung. Its purification, properties, and degradation of bradykinin. 153 67

Two polyclonal antisera were raised in rabbits to the phospholipase C-solubilized forms of pig renal dipeptidase (EC 3.4.13.11) and pig aminopeptidase P (EC 3.4.11.9). These antisera were purified and shown to cross-react with other glycosyl-phosphatidylinositol (G-PI)-anchored proteins isolated from pig, human and trypanosomes. The epitopes involved in this cross-reactivity were characterized by Western-blot analysis after mild acid or nitrous acid treatment of the G-PI-anchored proteins and by a competitive e.l.i.s.a. with other G-PI-anchored proteins and individual components of the anchor structure. These studies revealed that the primary epitope for both antisera is the inositol 1.2-(cyclic)monophosphate that is formed on phospholipase C cleavage of the intact G-PI anchor. Other minor epitopes, such as phosphoethanolamine, probably involve side-chain modifications to the core anchor structure that may be species-specific.
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PMID:Characterization of antibodies to the glycosyl-phosphatidylinositol membrane anchors of mammalian proteins. 170 60

Aminopeptidase P (EC 3.4.11.9) was solubilized from pig kidney membranes with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) and then purified by a combination of anion-exchange and hydrophobic-interaction chromatographies. Contaminating peptidase activities were removed by selective affinity chromatography. The purified enzyme was apparently homogeneous on SDS/PAGE with an Mr of 91,000. Enzymic deglycosylation revealed that aminopeptidase P is a glycoprotein, with up to 25% by weight of the protein being due to the presence of N-linked sugars. The phospholipase-solubilized aminopeptidase P was recognized by an antiserum to the cross-reacting determinant (CRD) characteristic of the glycosyl-phosphatidylinositol anchor. This recognition was abolished by mild acid treatment or deamination with HNO2, indicating that the CRD was due exclusively to the inositol 1,2-cyclic phosphate ring epitope generated by the action of PI-PLC. The activity of aminopeptidase P was inhibited by chelating agents and was stimulated by Mn2+ or Co2+ ions, confirming the metallo-enzyme nature of this peptidase. Selective inhibitors of other aminopeptidases (actinonin, amastatin, bestatin and puromycin) had little or no inhibitory effect.
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PMID:Purification and characterization of pig kidney aminopeptidase P. A glycosyl-phosphatidylinositol-anchored ectoenzyme. 213 78

The mode of membrane anchorage of three kidney microvillar membrane ectoenzymes has been examined. The release of aminopeptidase P (EC 3.4.11.9) from kidney membranes by bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) and the pattern of detergent solubilization of this ectoenzyme implies that it is anchored to the membrane via a covalently attached glycosyl-phosphatidylinositol moiety. As deduced by phase separation in Triton X-114, octyl-glucoside solubilized the amphipathic form of aminopeptidase P, whereas the PI-PLC-released form displayed hydrophilic properties. In contrast, the pattern of detergent solubilization of two microvillar carboxypeptidases and their resistance to release from the membrane by bacterial PI-PLC suggest that these two ectoenzymes are not anchored via phosphatidylinositol.
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PMID:Ectoenzymes of the kidney microvillar membrane. Aminopeptidase P is anchored by a glycosyl-phosphatidylinositol moiety. 327 35

The membrane-bound form of aminopeptidase P (aminoacylprolyl-peptide hydrolase) (EC 3.4.11.9) was purified 670-fold to apparent homogeneity from rat lung microsomes. The enzyme was solubilized from the membranes using a phosphatidylinositol-specific phospholipase C. The purification scheme also resulted in homogeneous preparations of dipeptidylpeptidase IV (EC 3.4.14.5) and membrane dipeptidase (EC 3.4.13.19). Aminopeptidase P had a subunit molecular weight of 90,000, which included at least 17% N-linked carbohydrate. The molecular weight by gel permeation chromatography varied from 220,000 to 340,000, depending on the conditions used. The amino acid composition was determined and the N-terminal sequence was found to be X1-Gly2-Pro3-Glu4-Ser5-Leu6-Gly7-Arg8-Glu9-As p10-Val11-Arg12-Asp13-X14-Ser15- Thr16-Asn17-Pro18-Pro19-Arg20-Leu21- X22-Val23-Thr24-Ala25-. Aminopeptidase P cleaved the Arg1-Pro2 bond of bradykinin with a kcat/Km of 5.7 x 10(5) s-1 M-1. N-Terminal fragments of bradykinin including Arg-Pro-Pro, but not Arg-Pro, were also cleaved. The enzyme was shown to have four binding subsites (S1, S1', S2'. S3'), the first three of which must be occupied for hydrolysis to occur. Neuropeptide Y and allatostatin I were hydrolyzed at the Tyr1-Pro2 bond and Ala1-Pro2 bond, respectively. The pH optimum for Arg-Pro-Pro cleavage was 6.8-7.5 in most buffers. The enzyme was most stable in the range of pH 7.0-10.5 in the presence of poly(ethylene glycol). NaCl inhibited activity completely at 2 M. Mn2+ had variable effects on activity, depending on its concentration and the substrate used. Various peptides having an N-terminal Pro-Pro sequence were inhibitory. The enzyme was also inhibited by EDTA, o-phenanthroline, 2-mercaptoethanol, dithiothreitol, p-(chloromercuri)benzenesulfonic acid, apstatin, and captopril. The carboxyalkyl angiotensin-converting enzyme inhibitors, ramiprilat and enalaprilat, inhibited activity in the micromolar range only in the presence of Mn2+.
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PMID:Purification and properties of membrane-bound aminopeptidase P from rat lung. 766 81

A polyclonal antiserum raised to the phospholipase C-solubilized form of membrane dipeptidase (EC 3.4.13.11) purified from human kidney was found to cross-react with unrelated trypanosomal and porcine glycosyl-phosphatidylinositol anchored proteins. Those antibodies recognising the cross-reacting determinant (CRD) were isolated by chromatography on a column of immobilized phospholipase C-solubilized porcine aminopeptidase P (EC 3.4.11.9), and the epitopes involved in the recognition were then characterized by immunoelectrophoretic blot analysis and by a competitive ELISA. The phospholipase C-solubilized forms of human and porcine membrane dipeptidase, porcine aminopeptidase P and trypanosome variant surface glycoprotein were recognised by the anti-CRD antiserum, and this recognition was abolished by prior treatment of the proteins with either mild acid or nitrous acid. In contrast, the detergent-solubilized, membrane-forms of human and porcine membrane dipeptidase were not recognised. Of a range of components of the glycosyl-phosphatidylinositol anchor, only inositol 1,2-cyclic monophosphate and the insulin-mimetic disaccharide, glucosaminyl-1,6-inositol 1,2-cyclic monophosphate, inhibited in the micromolar range the binding of the anti-CRD antiserum to immobilized porcine aminopeptidase P. These results indicate that the major epitope recognised by this anti-CRD antiserum is the inositol 1,2-cyclic monophosphate formed on phospholipase C cleavage of the glycosyl-phosphatidylinositol anchor.
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PMID:Characterization of an antibody to the cross-reacting determinant of the glycosyl-phosphatidylinositol anchor of human membrane dipeptidase. 767 86

The complement of brush border hydrolases provides an excellent model system for study of the structure, topology and assembly of plasma membrane proteins. Among the peptidases of the renal brush border are a number of glycosylphosphatidylinositol (GPI)-anchored proteins, especially membrane dipeptidase and aminopeptidase P. Affinity purification protocols have led to the isolation of homogeneous forms of these proteins and membrane dipeptidase has been cloned and expressed in Xenopus oocytes and Cos-1 cells. The core glycan structures of both human and porcine dipeptidase have been determined, allowing direct comparisons of the GPI anchors on the same protein in different species. Aminopeptidase P has been compared in the brush borders of pig kidney and intestine and may well be anchored in distinct ways in the two tissues. Immunological cross-reactivity of polyclonal antibodies to these two proteins has revealed the phospholipase C-cleaved GPI anchor as the common epitope and defined those components of the anchor important for recognition. These antibodies are also proving useful in characterizing GPI-derived mediators that may be involved in cell signalling processes. These abundant ectopeptidases offer a number of advantages for studies of the biochemistry of mammalian GPI anchors.
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PMID:Structural and immunological studies of GPI-anchored brush border hydrolases. 808 Dec 54

Pig kidney aminopeptidase P (AP-P; EC 3.4.11.9) has been purified to homogeneity after its solubilisation from brush border membranes by phosphatidylinositol-specific phospholipase C. The effects of various activators and inhibitors of AP-P activity have been examined with a number of different substrates for the enzyme. The hydrolysis of bradykinin and ArgProPro is inhibited at Mn2+ concentrations above 10(-5) M, whereas the hydrolysis of other substrates (GlyProHyp, beta-casomorphin, substance P) is substantially activated, with 4-10 mM Mn2+ being optimal. The thiol reagent, p-chloromercuriphenylsulphonic acid, inhibits the hydrolysis of GlyProHyp but markedly activates the hydrolysis of bradykinin. A number of inhibitors of angiotensin converting enzyme (ACE; EC 3.4.15.1), previously reported to inhibit the hydrolysis of GlyProHyp, have no effect on the hydrolysis of bradykinin except in the presence of Mn2+. Differences were also observed in the degree of inhibition of GlyProHyp and bradykinin hydrolysis by EDTA and their reactivation by divalent cations. The hydrolysis of GlyProHyp follows Michaelis-Menten kinetics with a Km value of 2.7 mM. Bradykinin inhibits GlyProHyp hydrolysis with an I50 of 1.4 microM. The hydrolysis of bradykinin by AP-P reveals anomalous nonlinear kinetics indicative of negative cooperativity or the presence of more than one active site for this substrate. These results indicate that substrates for AP-P can be divided into 2 groups based on their responses to inhibitors and cation activators.
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PMID:Inhibition and metal ion activation of pig kidney aminopeptidase P. Dependence on nature of substrate. 869 47


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