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)

The effects of atropine on pentagastrin-stimulated gastric secretion of water, H, Cl, Na, K, and pepsin were determined by kinetic analysis of dose-response studies in 5 dogs with esophagostomy and gastric cannula. First a dose-response study was done using 7 doses of pentagastrin (1-6 mug/kg hr), each dose given by I.V. infusion for 4 hr at a separate time. The same series of doses was used with atropine sulfate 10 mug/kg hr as background. Atropine inhibited pentagastrin-stimulated secretion competively with a dose ratio change of 20. In a third set of studies pentagastrin was infused alone for 4 hrs in the dose of 1.5 mug/kg hr and then with each of 7 doses of atropine (0.625-40 mug/kg hr), each dose used separately. Atropine competitively inhibited water, H, Cl, and K secretion, with Ki (dose of atropine giving 50% inhibition) of 1.0 mug/kg hr. Pepsin secretion was much more strongly inhibited than acid secretion by atropine with Ki 0.27 mug/kg hr and the inhibition was uncompetitive. Calculated maximal inhibition of H+ secretion by atropine was 89% and of pepsin 95%. Furthermore the shape of the response to pentagastrin was altered by atropine so that the peak response was delayed to the third and fourth hour of pentagastrin infusion.
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PMID:Kinetics of atropine inhibition of pentagastrin-stimulated H+, electrolyte, and pepsin secretion in the dog. 31 59

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

H+ and pepsin output were studied in four gastric fistula dogs with histamine and in five dogs with 4-methylhistamine (4(Me)H), an H2 histamine receptor agonist with little H1 effect. Each amine was given in 45-min incremental step doses to constitute full dose-response curves. Pepsin output was biphasic with both drugs. Peak pepsin output occurred at low doses (less than or equal to 5 microgram/kg-h) and progressive inhibition of output was seen at higher doses, but H+ output was stimulated at all doses. The H2 receptor antagonist, cimetidine, competitively inhibited H+ stimulation. The pepsin response to histamine or 4(Me)H was converted to a positive logsigmoid response when cimetidine was given at the same time. In the presence of cimetidine (1 mg/kg-h), the outputs of H+ and pepsin were positively correlated in the full histamine dose range. These data show that histamine effects on pepsin secretin are a mixture of stimulation and inhibition and that the receptor responsible for pepsin stimulation is of a high affinity, low Km, H2 type, whereas inhibition at high doses of histamine is probably mediated by a low affinity, high Km receptor, also H2 type.
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PMID:Evidence for a histamine H2 receptor that inhibits pepsin secretion in the dog. 33 42

New data on the specificity and mechanism of action of porcine pepsin are presented, including statistical analysis of protein cleavage by the enzyme, kinetics of synthetic substrates, enzyme inhibition and activation, kinetics of transpeptidation reaction, and 180 exchange studies. From these data it was concluded that pepsin has an extended active site being able to accomodate specifically five amino acid residues of the substrate. The orientation of the substrate molecule relative to the ethanol binding loci in pepsin crystals has been determined. Pepsin mechanism includes "amino-enzyme" formation which chemically is not an amide, formed by the enzyme carboxyl with the amino fragment of the substrate.
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PMID:New data on pepsin mechanism and specificity. 33 89

1. The influence of replacing 10% of the urea nitrogen in a purified diet with casein, maize gluten or white fish meal on the efficiency of conversion of dietary-N into microbial N was examined using sheep equipped with rumen fistulas and duodenal re-entrant cannulas. 2. Total nitrogen (TN), non-ammonia nitrogen (NAN) and amino acid nitrogen (AAN) flowing to the proximal duodenum were significantly higher (P smaller than 0.05) when maize gluten was added to the diet, and this appeared to be due to an increased efficiency of microbial protein production. 3. Pepsin secretion was not significantly different between treatments and the daily amount of pepsin N flowing to the proximal duodenum was very small (40-53 mg). The peak of pepsin activity in duodenal digesta was reached 6-8 h after feeding. 4. The possible practical implications of the results are discussed.
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PMID:The effect of partially replacing urea nitrogen with protein N on N capture in the rumen of sheep fed a purified diet. 33 43

Pepsin-soluble collagen was isolated from bovine vitreous humor. This collagen showed only one alpha-chain in disc electrophoresis, migrating in the alpha1-chain position and between the alpha- and beta-components some colored bands were visible. The disc electrophoretic patterns of the cyanogen bromide peptides of pepsin-soluble vitreous body collagen and pepsin-soluble type II collagen revealed no identity.
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PMID:[Comparison of the cyanogen bromide peptides of vitreous body collagen and type II collagen (author's transl)]. 34 37

Sequential extraction of mature rabbit corneal stroma with NaCl-Tris buffer and acetic acid solubilized only 12% of the total corneal collagen. Pepsin (E:S 1:10,4 degrees C, 48 hr) in 0.4 M acetic acid solubilized 91% to 95% of the total collagen in the residue. Approximately 68% of the solubilized material could be precipitated at 2.5M NaCl and a further 3% to 9% at 3.5M NaCl. The collagenous material precipitating at 2.5M NaCl contained alpha, beta, gamma, and some higher molecular weight components and had a CNBr profile similar to bovine type I skin collagen. It had an hydroxylysine/lysine (OHLys/Lys) ratio of 0.43, similar to that of skin collagen, but unlike skin collagen was 52% glycosyled. Although the 3.5M NaCl precipitate had a CNBr peptide profile similar to that of type I collagen, it contained two additional collagen chains of molecular weight approximately 140,000 and 100,000 daltons, had an OHLys/Lys ratio of 0.62, and was 66% glycosylated. Individual chains were separated from the collagen precipitates by gel electrophoresis,and the additional collagen chains were shown to be carbohydrate rich. These additional collagen chains may be derived from one or more molecular species which are physiologically important in the maintenance of the unique organization of corneal collagen.
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PMID:Collagen polymorphism in mature rabbit cornea. 34 41

Intraduodenal instillation of hypertonic glucose significantly inhibited tetragastrin-induced gastric acid and pepsin outputs in man. The secretory volume of gastric juice was markedly decreased, whereas, acid concentration remained unchanged. Pepsin concentration, on the contrary, was reduced significantly. The degree of inhibition of pepsin output, therefore, was greater than that of acid output. No significant difference in the extent of inhibition of acid or pepsin output was observed between control subjects and patients with duodenal ulcer.
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PMID:Inhibition of gastric secretion by intraduodenal hypertonic glucose in patients with duodenal ulcer. 34 51

The binding of Staph A protein to murine immunoglobulins has previously been thought to be restricted to the IgG2 and IgG3 classes. In this study five IgM proteins were assessed for binding, and of these one showed marked Staph A binding. Pepsin digestion of this IgM molecule produced several different sized fragments, and the binding studies with these fragments indicated that the binding site is in the CH2 domain.
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PMID:The binding of murine IgM to Staphylococcal A protein. 35 94

The effect of the osmolarity of intragastric instillates on pepsin secretion was studied in rats anaesthetised with urethane. Irrigation of the stomach with solutions of sucrose and NaCl, resp. caused a concentration-dependent increase in pepsin output. A stimulation was observed already by hypotonic solutions and the maximal effect was obtained by 300 m-osmole/l of sucrose and by 600 m-osmole/l of NaCl (13- and 10-fold stimulation resp.). A similar time course in the increase of pepsin output was produced by hyperosmotic solutions (600 m-osmole/l) of sucrose, urea, NaCl and choline chloride. Pepsin output was stimulated maximally within 30 min and decreased thereafter, but remained at about 4--6-fold higher levels than during the previous irrigation with distilled water. Replacement of hyperosmotic instillates by distilled water reduced pepsin secretion to the initial level. Hypertonic ethanol (600 m-osmole/l) increased pepsin output only slightly. Vagotomy, pretreatment with atropine (1 mg/kg i.v.) or cimetidine (5 mg/kg i.v.), local anesthesia of the gastric mucosa with 4% lidocaine or intravenous infusion of PGE2 (2 microgram/kg X min) did not antagonise the stimulation of pepsin output induced by hyperosmotic NaCl (600 m-osmole/l). The results indicate that the increase of the osmolarity of intragastric instillates stimulates pepsin secretion in the rat without involvement of neural (vagal or local cholinergic reflexes) or hormonal mechanisms (release of gastrin) which are known to stimulate gastric secretion in the gastric phase.
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PMID:Osmotic stimulation of pepsin secretion in the rat. 35 99


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