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 was found capable of splitting cycloota- and cyclodecapeptides cyclo (-L-leucyl-L-tyrosyl-glycln-), n=6 or 8. The 18-membered peptides cyclo(-L-leucyl-L-tyrosyl-glycyl4-) and cyclo(-L-leucyl-L-tyrosy-delta-aminovaleroyl2-) were found stable to the effect of pepsin. To study the kinectics of hydrolysis for tyrosine-containing substrates of pepsin, a method of isolation of the unsplit substrate using ion-exchange resins and quantitative spectrophotometric estimation by absortion of tyysis of cycoocta and cyclodecapeptides was characterized by Km and kcat values.
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PMID:[Conformational aspects of peptide interaction with proteolytic enzymes. Pepsin-catalyzed hydrolysis of cyclic peptides, containing leucyl-tyrosine fragments]. 110 81

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

Valosin, a novel 25-amino acid gastrointestinal peptide with N-terminal valine and C-terminal tyrosine, has recently been isolated from porcine upper gut extracts. Its physiologic role is unknown and it does not belong to one of the structurally related gut peptide families. Assuming that valosin may influence gastrointestinal functions, we investigated the effect of high-performance liquid chromatography-pure valosin on gastric and exocrine pancreatic secretion and on the intestinal myoelectric activity in conscious dogs. Intravenous injection of valosin (0.125-1 microgram/kg) dose-dependently increased gastric acid secretion 80-fold over basal, corresponding to 18% of the maximal pentagastrin-induced effect. Pepsin output increased 10-fold over basal (30% of the pentagastrin-stimulated secretion). Half-maximal stimulation by pentagastrin could be further increased dose-dependently by simultaneous administration of valosin. Pancreatic bicarbonate secretion was stimulated 11-fold over basal at 1.0 microgram/kg, reaching about 6% of the secretin-induced maximal output, whereas protein secretion increased 12-fold over basal, corresponding to about 55% of the cholecystokinin-induced maximal output. In fasted dogs, spontaneously occurring migrating myoelectric complexes were substantially delayed during infusion of valosin at a dose of 0.2 microgram/kg. These experiments indicate that valosin may represent a novel member of the regulatory gastrointestinal peptides.
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PMID:Valosin stimulates gastric and exocrine pancreatic secretion and inhibits fasting small intestinal myoelectric activity in the dog. 310 27

Pepsin-catalyzed transpeptidation was studied by high resolution 75 MHz 13C nuclear magnetic resonance spectroscopy. Enrichment with 13C at the carbonyl carbons of the substrates Leu-Tyr-NH2 and Leu-Leu-NH2 facilitated detection and identification of the transpeptidation and hydrolysis products of enzymic action. Porcine pepsin was found in each case to synthesize and release the tetrapeptide Leu-Leu-Leu-Leu as the primary product of transpeptidation, the longest oligomeric product of transpeptidation observed to date. Productive binding of the dipeptide substrates into the active site groove of pepsin required an induction period of several minutes. Quenching experiments suggested the presence of strongly bound intermediate forms of Leu and Leu-Leu prior to observation of any enzyme-free products. The finding of the tetrapeptide as a primary product is discussed as an instance where transpeptidation of the tripeptide competes successfully with the action of pepsin subsite S3 as a trigger for product release.
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PMID:Transpeptidation reactions of porcine pepsin. Formation of tetrapeptides from dipeptide substrates. 313 36

Pepsin-catalyzed synthesis of protected peptides was studied in two-phase systems containing up to 5% (by volume) of aqueous phase. A methodological study was carried out to determine the optimum conditions for the synthesis of the model protected peptide Z-Phe-Phe-OMe. Several parameters such as concentrations of carboxylic and amino components, pH of the aqueous phase, ratio of organic to aqueous phase volumes and nature of the organic solvent were investigated. It was observed that the most hydrophobic solvents produced the best yields, despite the low solubility of substrates in these media. The log P of the solvent could be used to predict the solvent effect over the reaction yields. Pepsin immobilized by adsorption onto the solid supports Celite and Chromosorb was employed to perform a study of secondary specificity of the enzyme in organic media through the coupling between Z-X-Phe-OH (X = Ala, Asp, Glu, Gly, Phe, Ile, Val, Trp and Tyr) and Phe-OMe. This investigation was performed in two solvent systems: (A) ethyl acetate:citrate buffer pH 4.5 (98:02, v:v) and (B) acetonitrile:citrate buffer pH 4.5 (96:04, v:v). Reaction rate data showed that pepsin had a preference for more hydrophilic substituents in the P2 position. These data are in contrast to the literature for a similar reaction performed in predominantly aqueous media. Thus, for mainly organic media, partition phenomena are very important and may cause an apparent modification of enzyme specificity.
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PMID:Pepsin-catalyzed peptide synthesis in organic media: studies with free and immobilized enzyme. 789 3

Conditions for the release of beta-casomorphin-7 from bovine beta-casein by gastrointestinal proteases in vitro were investigated. beta-Casomorphin-7 was released only from a genetic variant of beta-casein containing a His residue at the 67th position of the peptide chain. Elastase cleaved the peptide bond between Ile66 and His67, releasing the carboxyl terminus of beta-casomorphin-7. Pepsin and leucine aminopeptidase were required to release the amino terminus of this peptide. beta-Casomorphin-9, -13, and -21 also were isolated, and their opioid activities were measured. In this study, we also isolated a novel opioid peptide neocasomorphin-6 (Tyr-Pro-Val-Glu-Pro-Phe), which was released by action of trypsin or pepsin and chymotrypsin.
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PMID:Enzymatic release of neocasomorphin and beta-casomorphin from bovine beta-casein. 1050 74

The effects of 20 microg/ml exogenous arachidonic acid (AA) and prostaglandin A(2) (PGA(2)) were evaluated on total tyrosine kinase (TK) activity and tyrosine phosphorylation status in HeLa and MCF-7 cells. AA and PGA(2) increased TK activity in both HeLa and MCF-7 cells. Western blotting employing an anti-phosphotyrosine antibody showed only one protein of approximately 55 kDa (approximately 55 kDa) to be phosphorylated in the MCF-7 cells, while a variety of proteins were phosphorylated in the HeLa cells, including the approximately 55 kDa protein. Amino acid analyses as well as Matrix Assisted Laser Desorption Ionization were conducted on this protein from different cell lines and it was shown to be similar. Comparison to p53 did not show similarities. The identity of this protein needs to be further characterized to help elucidate the signal transduction pathways of AA and PGA(2).
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PMID:Identification of a tyrosine kinase-phosphorylated protein in arachidonic acid- and prostaglandin A(2)-treated cells in vitro. 1172 68

In many GL-7ACA acylases, the first Ser residue at the N-terminal of beta-subunit is the catalytic center. In order to investigate relationship between the N-terminal structure and catalytic activities, peptide replacement and site-directed mutagenesis were performed at the N-terminal of beta-subunit of GL-7ACA acylase C130. When the N-terminal 8 amino acid residues of C130 were replaced by the corresponding sequence of penicillin acylases PAC and PGA, respectively, the first mutant B8PAC lost the activity of the acylase, and the second mutant B8PGA had lower activity with the K(m) value increasing from 0.44x10(-3)mol.L(-1) to 0.55x10(-3) mol.L(-1), and the k(cat) decreasing from 4.92 s(-1) to 1.64 s(-1). Although the substitution of Trp (beta4) by Tyr did not change the K(m) value, the k (cat) decreased to 2.29 s(-1). When the Trp was substitued by Leu, both the K ( m ) and k ( cat ) values decreased. Compared with the wild type, mutations of Ser (beta3) to Met, Ala and Cys caused decrease of K(m) values by 52.27%, 43.18% and 38.64%, respectively. Mutation of Asn (beta2) to Gln caused the K ( m ) value being increased by 5-fold, and k ( cat ) decreased by 10-fold. These results suggested that the N-terminal amino acid residues of beta-subunit in GL-7ACA acylase C130 are important for enzyme function.
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PMID:Mutagenesis of N-terminal Amino Acid Residues in beta-subunit of Glutaryl-7-amino-cephalosporanic Acid Acylase C130. 1203 60

The following experimental results have been obtained. 1. Native egg albumin treated with iodine and then denatured no longer gives a nitroprusside test or reduces dilute ferricyanide in neutral Duponol PC solution. 2. More iodine is needed to abolish the ferricyanide reduction if the reaction between native egg albumin and iodine is carried out at pH 6.8 than if the reaction is carried out at pH 3.2. At pH 6.8 iodine reacts with tyrosine as well as with cysteine. 3. Cysteine and tryptophane are the only amino acids with reducing groups which are known to react with dilute iodine at pH 3.2 The reducing power of cysteine is abolished by the reaction with iodine, whereas the reducing power of tryptophane remains intact. Pepsin and chymotrypsinogen which contain tryptophane but not cysteine, do not react at all with dilute iodine at pH 3.2. 4. Native egg albumin treated with iodoacetamide at pH 9.0 and then denatured by Duponol PC reduces only 60 per cent as much dilute ferricyanide as egg albumin which has not been treated with iodoacetamide. 5. The SH group is the only protein reducing group which is known to react with iodoacetamide. The simplest explanation of the new observation that the SH groups of egg albumin can be modified by reactions with the native form of the protein is that the native egg albumin has free and accessible but relatively unreactive SH groups which can react with iodine and iodoacetamide despite the fact that they do not react with ferricyanide, porphyrindin, or nitroprusside. Preliminary experiments suggested by the results with egg albumin indicate that the tobacco mosaic virus is modified by iodine at pH 2.8 without being inactivated and that the tobacco mosaic and rabbit papilloma viruses are not inactivated by iodoacetamide at pH 8.0.
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PMID:THE REACTIONS OF IODINE AND IODOACETAMIDE WITH NATIVE EGG ALBUMIN. 1987 58


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