Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00790 (PGA)
 2,475 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Radioactive selenite reacts with purified human and goat immunoglobulins at acidic and neutral pH. The antigenic properties of the immunoglobulins are retained during the selenium labelling as shown by immunoelectrophoresis and autoradiography. Pepsin digests of 75Se-labelled IgG possess 75Se both in the (Fab')2 fraction and in the low molecular weight peptides derived from the Fc domains. Alpha-1-acid glycoprotein, ribonuclease, and lysozyme are also labelled by this procedure. Enhancement of 75Se incorporation by urea, guanidinium chloride, mercaptoethanol, sodium sulfite and carrier selenite is interpreted as an effect of destabilization of IgG disulfide bonds. Up to 1.4 g atoms Se per mol IgG have been incorporated. We assume that selenite is cleaving disulfides by a process akin to sulfitolysis. The lability of the isolated 75Se-labelled IgG to high concentrations of mercaptans and sulfite is consistent with this idea. These 75Se-labelled proteins may be useful in structure studies and radioimmunoassay.
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PMID:Reaction of selenium with immunoglobulin molecules. 1 84

1. The reactivities of phenylglyoxal (PGO), glyoxal (GO), and/or methylglyoxal (MGO) with several proteins, including ribonuclease A [EC 3.1.4.22] and its derivatives, alpha-chymotrypsin [EC 3.4.21.1], trypsin [EC 3.4.21.4], lysozyme [EC 3.2.1.17], pepsin [EC 3.4.23.1], rennin [EC 3.4.23.4], thermolysin, and insulin and its B chain, have been examined. From analyses of the reaction products, PGO was shown to be the most specific for arginine residues. GO and MGO also reacted rapidly with arginine residues, but they also reacted with lysine residues to a significant extent. A side reaction with N-terminal alpha-amino groups was observed with each of these reagents. 2. Two arginine residues out of four in ribonuclease A, two out of three in alpha-chymotrypsin, one out of two in trypsin, one out of two in pepsin, and one out of five in rennin appeared to react with PGO fairly rapidly, indicating a difference in the relative accessibility of these residues by the reagent. Extensive modification of the arginine residues by PGO occurred with RCM-derivatives of ribonuclease A and insulin B chain. The N-terminal isoleucine residues of alpha-chymotrypsin and trypsin appeared to be unreactive with PGO because of salt bridge formation with an aspartyl residue. The activity of alpha-chymotrypsin toward N-benzoyl-L-tyrosine ethyl ester and the lytic activity of lysozyme were lost rapidly on treatment with PGO, as in the case of ribonuclease A. Pepsin and rennin were only partially inactivated by reaction with PGO.
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PMID:Further studies on the reactions of phenylglyoxal and related reagents with proteins. 32 41

Pepsin successfully catalyzed the synthesis of several peptide derivatives from N-protected di- or tripeptides and amino acid or peptide esters or p-nitroanilides in dimethylformamide-water solutions at pH 4.6. An optimal substrates:pepsin ratio depended on the structure of starting peptides, especially their fit to the substrate binding sites of the enzyme. For hexapeptide Z-Ala-Ala-Phe-Leu-Ala-Ala-OCH3 formation, an equilibrium yield was attained at 1:3.10(5) enzyme-substrates ratio that indicated high efficiency of pepsin in synthesis reactions. In the course of the equilibrium peptide synthesis, pepsin gradually disappeared from the liquid phase due to its entrapment within a gel, formed by the hexapeptide product, while retaining its activity. The inclusion into the precipitate was not specific for pepsin, so far as inert proteins, lysozyme, ribonuclease A and carbonic anhydrase, when added to the reaction mixture, became also co-precipitated with the hexapeptide formed. It appears that co-precipitation of pepsin, an important factor limiting the enzyme efficiency, might be operative as well for other proteinases used to catalyze peptide synthesis.
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PMID:Pepsin as a catalyst of peptide synthesis. Enzyme co-precipitation with emerging peptide products. 142 33

The Streptococcus mutans group b antigen of strain FA1 has been defined as to chemical composition and immunological specificity. The antigen in cold trichloroacetic acid extracts was fractionated on diethylaminoethyl-Sephadex A-25 at pH 8.5. Two forms were isolated: a polysaccharide and a mucoprotein. The two polymers reacted as a single substance in agar gel diffusion against specific adsorbed FA1 rabbit antisera but were separated by gel immunoelectrophoresis. No reaction with any other S. mutans or streptococcal group sera occurred. Galactose composed about one-third and galactosamine about 3% of the total weight of each polymer. Rhamnose was a major component of the polysaccharide (47%) but was present only in traces in the mucoprotein. The protein content of the latter was about 40%. No significant quantities of glycerol, phosphorus, or muramic acid were present in either case. Pepsin and trypsin had no effect on the serological specificity of the mucoprotein. d-Galactose and d-galactosamine were strong inhibitors (70%) of the precipitin reaction, whereas d-glucose, d-glucosamine, and N-acetyl-d-glucosamine inhibited between 25 and 35%. The results indicate that the antigen is a major antigenic component of the cell wall and that the specificity of the antigen resides in binding sites which contain both d-galactose and d-galactosamine. Agglutination of whole cells by specific group b antiserum indicates the antibody receptor sites of the polysaccharide antigen are at the surface of the streptococcal cell. The mucoprotein, but not the polysaccharide, was released from the cell by lysozyme. Lysis did not occur. The immunological specificity and other characteristics of the antigen establishes it as the identifying antigen of S. mutans group b.
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PMID:Structure and immunological specificity of the Streptococcus mutans group b cell wall antigen. 412 3

1. With the aid of a coupled system involving glutathione reductase, the reaction of glutathione with the disulphide bonds of purified proteins has been studied. 2. Bovine serum albumin, conalbumin, lysozyme, trypsin inhibitors from egg white, lima bean and soya bean either did not react with glutathione or reacted only slightly. With these proteins reactivity was markedly increased by limited proteolysis. 3. Bovine and human gamma-globulins, fibrinogen and beta-lactoglobulin exhibited some reactivity (less than 15%) with glutathione and again this was increased by limited proteolysis. Pepsin, trypsin and chymotrypsin exhibited greater reactivity than the proteins previously mentioned. Di-isopropylphosphoryl-chymotrypsin exhibited less reactivity than chymotrypsin, suggesting that autolysis under the experimental conditions used contributed towards the reactivity of this protein. Proteolysis also increased the reactivity of these proteins. The three disulphide bonds of insulin were reduced by glutathione. 4. Above 35 degrees the disulphide bonds of serum albumin show a progressive increase in reactivity and at 55 degrees half of the bonds become accessible to glutathione. 5. From the results obtained with the proteins investigated, the conclusion reached is that the disulphide bonds of native proteins are structurally protected and do not react with glutathione under physiological conditions.
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PMID:The reactivity of the disulphide bonds of purified proteins in relationship to primary structure. 486 Apr 70

The possibility of preservation and restoration of antigenicity of some antigens in paraffin-embedded tissue was evaluated by direct immunofluorescent technique on deparaffinized sections. Fixation with 96% ethanol-1% acetic acid, 10% neutral buffered formalin and p-formaldehyde was useful for the preservation of tissue antigens and immune deposits, whose antigenicity could be easily restored by trypsin digestion. Neutral buffered formalin was also a satisfactory fixative in immunofluorescent staining on lymphocyte/plasma cell-bound immunoglobulins. Fixation with alcohol-Bouin's fluid showed contrast results; feasible for staining of cell-bound immunoglobulins, but poor for that of glomerular immune deposits. After papain digestion, BSA and lysozyme, antigens of immune complexes, were easily detected in experimental chronic serum sickness glomerulonephritis. Pepsin was more efficient than trypsin in restoring the antigenicity of renal tissue antigens such as fibronectin and polyantigenic basement membrane, but the brush border antigen of the proximal renal tubules was frail to the pepsin digestion. In general, the enzymatic digestion time necessary for the restoration of antigenicity was in parallel with fixation time. Results obtained have shown that deparaffinized sections could be used as satisfactory substrate for immunohistochemistry when proper fixation and efficient proteolytic enzymatic pretreatments were performed.
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PMID:Restoration of antigenicity of tissue antigens, cell-bound immunoglobulins and immune deposits in paraffin-embedded tissue. The influence of fixation and proteolytic enzymatic digestion. 643 48

Bovine spinal cord protein from peripheral nerve (BSCP-PN) was detected in the soluble fraction of the initial 0.8 M sucrose homogenate of bovine peripheral nerves by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The BSCP-PN in the soluble fraction of the 0.8 M sucrose homogenates was 25% of the BSCP-PN found in the soluble fraction of 0.3 M NaCl homogenates of peripheral nerve. BSCP-PN was also identified in purified bovine peripheral nerve myelin by immunodiffusion analyses and by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Densitometry data indicated that the BSCP-PN in myelin decreased from 25% of the total protein to approximately 8% when myelin was extracted with 0.3 M NaCl or 0.05 M HCl. The protein that remained in the BSCP-PN band of the NaCl-extracted myelin was identified as the periodic acid-Schiff II glycoprotein of peripheral myelin. Basic proteins such as BSCP-PN or lysozyme bound to myelin and to NaCl-extracted myelin when they were added to homogenates of myelin in 0.8 M sucrose. Pepsin, an acidic protein, did not bind to myelin under the same conditions. The results suggest that in 0.8 M sucrose, positively charged BSCP-PN released from the cytoplasm by homogenization binds to negatively charged myelin; thereafter, the BSCP-PN-myelin complex remains intact until it is dissociated in media of sufficiently high ionic strength. This interpretation is consistent with the immunohistological studies which demonstrated that BSCP-PN was not in the myelin sheath but was clearly localized in axons and in, or adjacent to, the Schwann cell basement membrane.
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PMID:Evidence that the bovine spinal cord protein is not an intrinsic component of peripheral myelin. 676 1

As part of a study of protein denaturation in foam we have measured the surface tension and the changes in protein structure occurring at the interface for lysozyme, pepsin, BSA, YADH, IgG, and catalase. The apparent CMC values were found to be dependent on the size and rigidity of the molecule. The variability of protein damage at a gas-liquid interface in foam was assessed using these proteins. The foams were produced under controlled conditions in a bubble column and were found to induce conformational changes in the protein molecules, but no fragmentation or disassociation of subunits occurred. Tertiary structural changes were detected in all the proteins studied, with some proteins forming aggregates. For pepsin, the secondary structure was also found to be altered. Enzyme solutions were used to determine the degree of biological activity retained after foaming for proteins with different structural characteristics. The more rigid proteins were found to display a low surface activity and a low degree of damage in foam. Pepsin suffered the highest rate of damage, which is thought to be a result of its inability to refold following denaturation. Copyright 1999 Academic Press.
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PMID:Protein Denaturation in Foam. 1041 68

The partly folded states of protein members of the lysozyme (LYS)/alpha-lactalbumin (LA) superfamily have been analyzed by circular dichroism (CD) measurements and limited proteolysis experiments. Hen, horse, dog, and pigeon LYSs and bovine LA were used in the present study. These are related proteins of 123- to 129-amino-acid residues with similar three-dimensional structures but low similarity in amino acid sequences. Moreover, notable differences among them reside in their calcium-binding properties and capability to adopt partly folded states or molten globules in acid solution (A-state) or on depletion of calcium at neutral pH (apo-state). Far- and near-UV CD measurements revealed that although the structures of hen and dog LYS are rather stable in acid at pH 2.0 or at neutral pH in the absence of calcium, conformational transitions to various extents occur with all other LYS/LA proteins herewith investigated. The most significant perturbation of tertiary structure in acid was observed with bovine LA and LYS from horse milk and pigeon egg-white. Pepsin and proteinase K were used as proteolytic probes, because these proteases show broad substrate specificity, and therefore, their sites of proteolysis are dictated not by the specific amino acid sequence of the protein substrate but by its overall structure and dynamics. Although hen LYS at pH 2.0 was fully resistant to proteolysis by pepsin, the other members of the LYS/LA superfamily were cleaved at different rates at few sites of the polypeptide chain and thus producing rather large protein fragments. The apo-form of bovine LA, horse LYS, and pigeon LYS were attacked by proteinase K at pH 8.3, whereas dog and hen LYSs were resistant to proteolysis when reacted under identical experimental conditions. Briefly, it has been found that the proteolysis data correlate well with the extent of conformational transitions inferred from CD spectra and with existing structural informations regarding the proteins herewith investigated, mainly derived from NMR and hydrogen exchange measurements. The sites of initial proteolytic cleavages in the LYS variants occur at the level of the beta-subdomain (approximately chain region 34-57), in analogy to those observed with bovine LA. Proteolysis data are in agreement with the current view that the molten globule of the LYS/LA proteins is characterized by a structured alpha-domain and a largely disrupted beta-subdomain. Our results underscore the utility of the limited proteolysis approach for analyzing structure and dynamics of proteins, even if adopting an ensemble of dynamic states as in the molten globule.
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PMID:Partly folded states of members of the lysozyme/lactalbumin superfamily: a comparative study by circular dichroism spectroscopy and limited proteolysis. 1244 91

A miniaturized pepsin reactor was prepared inside a fused-silica capillary (i.d. 75 microm) by coating a pepsin-containing gel on a photopolymerized porous silica monolith. The pepsin-encapsulated film was prepared by a sol-gel method. The sol-gel reaction was optimized so that the sol solution containing pepsin forms a thin film on the photopolymerized sol-gel (PSG) monolith that was initially fabricated at the inlet of the capillary. Pepsin was encapsulated into the gel matrix without losing its activity. The large surface area of the PSG monolith enabled the immobilized pepsin to achieve a high catalytic turnover rate, and the porous nature of the PSG promotes penetration of large molecular proteins into the column. The immobilized pepsin-digested peptides and proteins, and the resulting mixture of peptide fragments, could be directly separated in the portion of the capillary where no PSG monolith exists. The durability and repeatability of the fabricated pepsin-coated column was tested and found to be satisfactory. An acidic solution consisting of 0.5 M formic acid was used as the running buffer, because it suppresses the adsorption of proteins or peptides on the inner surface of the capillary as well as enables direct connection of the output of the capillary electrophoresis column to a mass spectrometer. The on-line digestion of insulin chain beta and lysozyme provides identification of the proteolytic peptides. Recovery was achieved for 100% of the insulin chain beta amino acid sequence and 73% of the lysozyme amino acid sequence.
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PMID:Integration of on-line protein digestion, peptide separation, and protein identification using pepsin-coated photopolymerized sol-gel columns and capillary electrophoresis/mass spectrometry. 1505 49


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