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)

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

Pepsin was shown to catalyze synthesis of esters or p-nitroanilides tri-, tetra-, penta- and hexapeptides of general formula Z-X-Y-B, where X = Ala-Phe, Phe-Met, Ala-Ala-Glu, Ala-Ala-Phe, Ala-Ala-Leu, Ala-Ala-Trp, Ala-Ala-Met. Y = Ala, Leu, Val, Phe, Arg, Ala-Ala, Gly-Gly, Leu-Ala-Ala, Phe-Ala-Ala. B = OMe, pNA. The reactions were carried out in dimethylformamide-water solutions at pH 4.6 by equimolar ratio of amino- and carboxyl components (with the exception of Arg-pNA taken in 2-fold excess). The amount of pepsin in the reaction approached 1:1700 enzyme: substrate molar ratio although it might be improved--up to 1:3.10(5) for relatively long peptides.
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PMID:[Pepsin in the enzymatic synthesis of esters and n-nitroanilide peptides]. 144 35

Pepsin catalyzed peptide synthesis in biphasic systems containing more than 95% (v/v) of organic phase was studied. Good yields were only obtained with more hydrophobic solvents, in spite of the low solubility of the substrates. The effects of the following parameters were also investigated: concentration of amino and carboxylic components, pH and buffer concentration, ratio between the aqueous and organic phases. The influence of different amino acid residues in the P2 position was investigated through the coupling between Z-Xyz-Phe-OH (where Xyz = Ala, Phe, Trp and Tyr) and Phe-OMe.
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PMID:Pepsin-catalyzed peptide synthesis in biphasic systems. 182 69

The technique of cassette and site-specific mutagenesis were used to study the role of residue No. 177 in penicillin G acylase (PGA, EC 3.5.1.11). Ser is conserved at residue No. 177 in all penicillin binding proteins. We got a series of mutants in which the amino acid at residue No. 177 was replaced by other amino acids through the site-specific and cassette mutagenesis, and we characterized the mutants by colony hybridization, NIPAB paper test and DNA sequence analysis. These mutants all show no activity of enzyme, even if the Ser residue was replaced by Thr, Gly and Ala respectively. The results show that Ser residue may be essential for substrate-binding or catalysis of PGA.
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PMID:[Effect of mutagenesis at Ser 177 residue in penicillin G acylase on activity of the enzyme]. 190 33

To exploit the well documented effect of 2,3-diphosphoglyceric acid (2,3-DPG) in enhancing oxygen delivery by human erythrocytes, we have investigated whether the DPG synthase/phosphatase enzyme system can be targeted to increase DPG levels in the cell. The hydrolytic activity (phosphatase) of the DPG metabolizing enzyme complex exhibits a marked dependence on a physiological effector, 2-phosphoglycolate. Little phosphatase activity is detected in the absence of this activator irrespective of the concentrations of the substrate. The phosphoglycolate-dependent phosphatase activity is competitively inhibited by a glycolytic intermediate, 3-phosphoglyceric acid (3-PGA). The 3-PGA inhibition persists when the 2,3-DPG concentration is raised to saturation level. In contrast, 3-PGA enhances the DPG synthase activity in a dose-dependent manner. In intact red cells, one-half of the cellular DPG content is depleted after 6 hr at 37 degrees C in glucose-free medium. The rate of 2,3-DPG degradation is accelerated when the cellular level of phosphoglycolate is increased by incubation with exogenous glycolate. Together, these results indicate that 2,3-DPG content in erythrocytes can be directly regulated through modulation of phosphatase/synthase activities. In support of this notion, a pyruvate kinase inhibitor, L-alanine, increases by 2-fold the cellular 3-PGA level. This is accompanied by a significant increase (30%) in 2,3-DPG content in human red blood cells. It is postulated that the DPG-promoting action of 3-PGA is mediated through simultaneous phosphatase inhibition and synthase activation. Furthermore, as a result of increased DPG accumulation, the oxygen-hemoglobin dissociation curve in L-alanine-treated cells is rightward shifted by 2.5 torr.
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PMID:2,3-Diphosphoglycerate phosphatase/synthase: a potential target for elevating the diphosphoglycerate level in human red blood cells. 215

1. Pepsin II extracted from the gastric mucosa of Scyliorhinus canicula has been characterized and compared to calf chymosin. 2. The kcat and Km of the dogfish enzyme for the synthetic hexapeptide Leu-Ser-Phe(NO2)-Nle-Ala-Leu-OMe have been determined. The kcat/Km ratio is close to that of calf chymosin. Its milk-clotting efficiency is however 21-fold lower than that of calf chymosin. 3. The proteolytic activity against haemoglobin is optimal at pH 2.5. It clots the milk up to pH 6.8. 4. The dogfish pepsin II shows relatively better activity at low temperatures than calf chymosin.
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PMID:Characterization of a chymosin-like pepsin from the dogfish Scyliorhinus canicula. 312 28

The primary structure of rat liver microsomal glutathione transferase has been determined. The 14C-carboxymethylated protein was fragmented with CNBr and proteolytic enzymes. The basis of the analysis was information from sequenator degradations of the intact protein, the largest CNBr fragment, and a large COOH-terminal fragment derived from a digest with Glu-specific staphylococcal protease. Remaining, smaller fragments were analyzed with the manual dimethylaminoazobenzene isothiocyanate method. Pepsin and limited acid hydrolysis were used to obtain peptides to confirm and overlap hydrophobic structures in the COOH-terminal half of the protein where trypsin and chymotrypsin failed to give any cleavage. Combined, these data permit the deduction of a 154-residue amino acid sequence. No evidence for micro-heterogeneity was obtained. The NH2-terminal alanine residue has a free alpha-amino group and the cysteine residue involved in activation of the enzymatic activity by sulfhydryl reagents is at position 49. The protein chain contains three regions with predictions for long beta strand secondary structures (positions 11-26, 103-120, and 131-145). Predictions may be inaccurate in membrane-associated proteins, but two of these regions also affect the three most hydrophobic segments. Thus, residues 11-35 form a long, largely hydrophobic part interrupted by only one charged residue (Lys-25), and residues 81-97 and 114-126 constitute the most hydrophobic segments directly noticeable from the hydrophilicity curve of the protein chain. These special parts of the molecule are of interest in relation to membrane interactions.
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PMID:Microsomal glutathione transferase. Primary structure. 393 48

Camel (Camelus dromedarius) pepsins were precipitated from the extract of the fundic gastric mucosa by ammonium sulfate between 35 and 80% saturation. DEAE--cellulose chromatography of this fraction produced two isoenzymes, I and II, which were further purified to homogeneity on sephadex G-100. Their Km with N-acetyl-L-phenylalanyl-diiodotyrosine were 0.10 and 0.90 mM, and their molecular weights which were determined on sodium dodecylsulfate gel electrophoresis exhibited 35,500 and 34,700, respectively. The two pepsins were essentially free of carbohydrates, but contained 0.3 and 1.0 mol of organic phosphate per 1 mol of protein, respectively. The apparent mobilities of the phospho- and dephosphoforms of each pepsin were indifferent in polyacrylamide gel electrophoresis at pH 8.9. The N-terminal residues of pepsins I and II were found to be alanine and leucine, respectively. Pepsin I was inactivated at a faster rate than that of pepsin II at pH 8 and 0 degrees C, and at pH 7.5 and 37 degrees C; but both were denatured under these conditions. The properties of these enzymes are compared with those of other mammalian and avian pepsins.
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PMID:Isolation and characterization of camel pepsins. 614 Oct 27

The pools of Arg, Gly, His, Ile, Ser, Glu, Leu, Val and Asp were lower during photosynthesis at 1% O2 concentration. At the same time specific radioactivity of a number of amino acids--following 14CO2 incorporation--was different than that at atmospheric O2 concentration. This is probably due to the inhibition of the photorespiratory nitrogen cycle and the resulting NH+4 deficiency. The pattern of response to O2 concentration suggests that in rye plants in the light, all Gly and a part of Ser are synthesized by an O2-sensitive pathway, i.e. via the glycolate pathway, but most of Ser is probably formed from 3-phosphoglycerate (3-PGA) via the O2-insensitive pathway. Changes in the pool size and specific radioactivity after 6 h incubation in darkness suggest that synthesis of Gly is strongly light-dependent, whereas synthesis of Ser was substantial also in darkness. The specific radioactivity of Ala, Asp, Ser and Glu indicates that in darkness those amino acids are formed from a common precursor, i.e. glycolytic 3-PGA, and undergo rapid metabolic turnover.
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PMID:Photosynthesis in detached rye leaves at normal and low oxygen concentration. II. Incorporation of 14CO2 into amino acids. 681

The characteristics of long-term potentiation (LTP) in the hippocampus of rats prenatally exposed to ethanol and treated postnatally with nootropic compounds L-pyroglutamyl-D-alanine-amide (L-pGlu-D-AlaNH2, PGA) or piracetam were studied using in vitro slice preparations. LTP was induced in the CA1 region by the orthodromic stimulation of the stratum radiatum with one train of 100 pulses (100 Hz, 1 s). The probability of LTP development in the hippocampus of young rats was significantly reduced by prenatal exposure to alcohol. This plasticity deficit was completely reversed by daily injections of PGA, 1 mg/kg for 12 days (8-19 days of postnatal development) but not of piracetam, 100 mg/kg. PGA (0.5 microM) also prevented the inhibition of LTP development in hippocampal slices perfused with ethanol, 20 or 50 mM. The data indicate that PGA effectively restores synaptic plasticity after both prenatal and acute exposure to ethanol and suggest that impaired LTP may be a useful model for studying the mechanisms of action of nootropic compounds.
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PMID:Nootropic compound L-pyroglutamyl-D-alanine-amide restores hippocampal long-term potentiation impaired by exposure to ethanol in rats. 760


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