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 isozymogens PGA-3 and PGA-5 of human pepsinogen A were digested with endoproteinase Lys-C. The peptides were separated by reverse-phase HPLC. PGA-5 showed a peak strongly absorbing at 254 nm absent in PGA-3. Analysis of amino acid composition using the Pico-Tag methodology combined with DABITC-sequencing reveals the sequence Tyr-Phe-Pro-Gln-Trp-Lys (peptide 37-43 of the activation segment). This confirms a study at the DNA level by our group [16] suggesting a Glu greater than Lys mutation at position 43 in the activation segment of PGA-5. Furthermore, it is proposed that the number of genetic variants of PGA is higher than is actually seen by electrophoresis.
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PMID:Identification of a Glu greater than Lys substitution in the activation segment of human pepsinogen A-3 and -5 isozymogens by peptide mapping using endoproteinase Lys-C. 290 84

Pepsin and gastricsin from human gastric juice were separated by affinity chromatography on Sepharose 4B containing the immobilized synthetic inhibitor of aspartic proteinases, Val-D-Leu-Pro-Phe-Phe-Val-D-Leu. These enzymes were bound to the support at low pH, and gastricsin was released at the same pH with buffer containing 20% dioxan. Pepsin was not released under these conditions, but was eluted at higher pH with buffer also containing 20% dioxan. To obtain perfect separations, it is recommended to use diluted samples. Proteinases from the homogenate of human gastric mucosa are isolated on DEAE-cellulose before separation by affinity chromatography. Pepsin and gastricsin from human gastric juice and human gastric mucosa separated on DEAE-cellulose and isolated by affinity chromatography, were electrophoretically pure.
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PMID:Separation of human pepsin and gastricsin by affinity chromatography with an immobilized synthetic inhibitor. 308 53

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 angiogenin is 33% identical to that of bovine pancreatic ribonuclease (RNase), but the enzymatic activities of the two proteins differ markedly. Similarly, their susceptibilities to limited proteolysis differ as well. In contrast to RNase, angiogenin totally resists proteolysis by subtilisin. Indeed, among 16 proteases examined, only endoprotease Lys-C, trypsin, and pepsin are able to cleave angiogenin. Even with prolonged incubation, endoprotease Lys-C selectively cleaves the Lys-60-Asn-61 bond; the product retains full ribonucleolytic activity. Initially, trypsin also cleaves this same bond, but with time it causes extensive degradation. Pepsin, at pH 2, cleaves the Phe-9-Leu-10 bond, to give angiogenin (10-123), which displays approximately 15% of the native activity toward ribosomal RNA (rRNA). The susceptibility to proteolysis and/or the sites of cleavage of angiogenin and bovine RNase differ markedly despite their structural homology. These differences are considered in terms of the amino acid sequences of the two proteins.
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PMID:Conformational characterization of human angiogenin by limited proteolysis. 315 Dec 51

Human pepsinogen A3 and A5 have been purified to chromatographic and electrophoretic homogeneity. At pH 2 pepsinogen A3 activates at a much faster rate than pepsinogen A5. Leu-23-Lys-24 is the first bond cleaved during activation of pepsinogen A3. This bond is also cleaved in pepsinogen A5, but together with the cleavage of Asp-25-Phe-26. Amino acid sequencing shows that pepsinogen A3 has Glu at position 43, whereas pepsinogen A5 has Lys.
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PMID:Activation of human pepsinogens. 319 40

Apolipoprotein AI of human high-density lipoproteins is secreted by hepatocytes as a proapolipoprotein with a N-terminal hexapeptide sequence (Arg-His-Phe-Trp-Gln-Gln-) which differs from the prosequence of rat apolipoprotein AI (Trp-Asp-Phe-Trp-Gln-Gln). The two proteins have in common the unusual cleavage site -Gln-Gln-Asp-Glu-. It is hydrolysed by a specific serum proteinase with the release of mature apo AI. We synthesized a model substrate for the study of the final processing of pro-apo AI by the serum proteinase. It is an undecapeptide embracing the human pro-hexapeptide sequence and the first five N-terminal residues of apo AI, covalently linked to a hydrophilic resin. The N-terminal arginine residue was 3H-labelled. [formula; see text] This sequence was not cleaved by human serum under the conditions under which rat serum processes the pro-form of apo AI secreted by rat hepatocytes. Pepsin and chymotrypsin fragmented the undecapeptide at sites characteristic for these proteinases. We conclude that the proteolytic cleavage at the specific site (-Gln-Gln-Asp-Glu-) requires the correct conformation in addition to the specific amino-acid sequence.
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PMID:Processing of proapolipoprotein AI requires specific conformation. 392 Oct 42

Pepsin reacts stoicheiometrically with the active-site-directed irreversible inhibitor N-diazoacetyl-l-phenylalanine methyl ester, with concomitant loss of all proteolytic and peptidolytic activity. The reagent esterifies a unique aspartic acid residue in pepsin, which is in the sequence:Ile-Val-Asp-Thr-Gly-Thr-Ser
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PMID:An aspartic acid residue at the active site of pepsin. The isolation and sequence of the heptapeptide. 489 1


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