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Inhibition of pepsin by analogues of pepsinogen-(1-12)-peptide with substitutions in the 4-7 sequence region.

ABSTRACT: Derivatives of the 1-12 sequence of pig pepsinogen were prepared by solid-phase peptide synthesis. The three derivatives contain substitutions in the 4-7 region of the 1-12 sequence. Glycine was used to replace the hydrophobic residues -Val-Pro-Leu-Val- in pairs. After cleavage and purification, the synthetic peptides were compared with a synthetic peptide of the native sequence, prepared at the same time, with respect to their ability to inhibit the pepsin-catalysed clotting of milk. Inhibitory potency, determined from plots of percentage inhibition versus concentration of synthetic peptide, is inversely correlated with the substitution of glycine residues for the hydrophobic residues. Therefore the equilibrium inhibition of pepsin by these peptides is dominated by the hydrophobic nature of the 4-7 sequence region.

SUBMITTER: Dunn BM

PROVIDER: S-EPMC1154101 | biostudies-other | 1983 Feb

REPOSITORIES: biostudies-other

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PEPSINOGEN B: THE ZYMOGEN OF PEPSIN B.

Project description:1. Pepsinogen B, the precursor of pepsin B, has been isolated by ion-exchange chromatography and gel filtration from neutral extracts of pig gastric mucosa. The material possesses potential activity against acetyl-l-phenylalanyl-l-di-iodotyrosine and against gelatin but has little, if any, potential activity against haemoglobin. 2. The material appears homogeneous in the ultracentrifuge, but on gel filtration and on electrophoresis in starch gel it is shown to be contaminated with a small amount of material having potential activity against haemoglobin. On electrophoresis in starch gel also the material is shown to contain about equal amounts of two major components, both of which have potential activity against the synthetic substrate. Pepsin B has also been shown to contain two active components by electrophoresis under the same conditions. 3. The zymogen is similar to pepsinogen and pepsinogen C in its molecular weight and general physico-chemical properties, but differs from these zymogens in the nature of its N-terminal residues. It is possible that one of the components contains 1 mole of bound phosphate/mole. 4. The material is activated rapidly at pH2 and more slowly at pH4. At both pH values the kinetics of the activation reaction are complex.

| S-EPMC1206901 | biostudies-other

The inhibition of pepsin-catalysed reactions by structural and stereochemical product analogues.

Project description:1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. Inhibitors of the l-configuration give rise to linear non-competitive inhibition, whereas those of the d-configuration show linear competitive behaviour. 3. Non-competitive inhibition by the product N-acetyl-l-phenylalanine indicates an ordered release of products, which supports a common mechanism (involving an ;amino-enzyme') for pepsin-catalysed transpeptidation and hydrolysis reactions. 4. The differences in the types of inhibition caused by product analogues of the l- and d-series emphasize the stereospecificity of the binding of these inhibitors to free enzyme and to the putative amino-enzyme intermediate. 5. The results suggest that it is the anion of the acyl product that is released first in the hydrolytic reaction (see Kitson & Knowles, 1971).

| S-EPMC1176768 | biostudies-other

Pepsinogen C and pepsin C. Further purification and amino acid composition.

Project description:Pepsinogen C and pepsin C from the pig have been further purified by chromatography on DEAE-cellulose and by exclusion chromatography and the specific activities (with haemoglobin substrate) found are higher than those previously reported. The final preparations are homogeneous on electrophoresis in starch gel at three pH values except for contamination with less than 4% of pepsinogen and pepsin respectively. Pepsinogen C, like pepsin C, contains no phosphate. The amino acid compositions show some marked differences from those of pepsinogen and pepsin especially in the content of basic amino acids, glutamic acid, aspartic acid, leucine and isoleucine. The molecular weights of the enzyme and zymogen, obtained from the amino acid compositions, are 41400 and 36000 respectively, similar to those of pepsinogen and pepsin.

| S-EPMC1270080 | biostudies-other

Conversion of pepsinogen into pepsin is not a one-step process.

Project description:By incubation of pepsinogen with pepstatin at pH2.5, the first 'active' protein generated on activation is trapped in an inactive complex. The first activation peptide liberated has been identified as residues 1-16 from the pepsinogen sequence. This suggests a sequential mechanism rather than a one-step formation of pepsin.

| S-EPMC1172551 | biostudies-other

Depolarization of the intrinsic and extrinsic fluorescence of pepsinogen and pepsin.

Project description:1. The effects on the intrinsic tryptophan emission anisotropy of pepsin and pepsinogen solutions produced by (a) changes in temperature, (b) increases in viscosity with added glycerol at constant temperature and (c) decreases in lifetime through collisional quenching by potassium iodide were measured at several excitation wavelengths. The rotational-relaxation times calculated from results provided by method (b) approximate to the theoretical values for the two proteins, on taking hydration and shape factors into account, on the basis of random orientation of the tryptophan groups within the macromolecules. Differences between the results provided by methods (b) and (c) are attributable to inter-tryptophan resonance-energy-transfer depolarization, and the anomalous values recorded in method (a) can be attributed to the temperature-dependence of the limiting anisotropies. 2. Two different monomeric conjugates of pepsin, each containing one extrinsic fluorescent group per macromolecule, gave widely different relaxation times. This difference may arise from a specific orientation of the emission dipole in the enzyme. In active-site-labelled pepsin (1-dimethylaminonaphthalene-5-sulphonylphenylalanine-pepsin) this orientation would be approximately parallel to the symmetry axis of the equivalent ellipsoid, whereas in the other conjugate (1-dimethylaminonaphthalene-5-sulphonyl-pepsin) the orientation may be roughly normal to this direction, or some independent rotation of parts of the protein molecule is possible.

| S-EPMC1185371 | biostudies-other

Acidic digestion in a teleost: postprandial and circadian pattern of gastric pH, pepsin activity, and pepsinogen and proton pump mRNAs expression.

Project description:Two different modes for regulation of stomach acid secretion have been described in vertebrates. Some species exhibit a continuous acid secretion maintaining a low gastric pH during fasting. Others, as some teleosts, maintain a neutral gastric pH during fasting while the hydrochloric acid is released only after the ingestion of a meal. Those different patterns seem to be closely related to specific feeding habits. However, our recent observations suggest that this acidification pattern could be modified by changes in daily feeding frequency and time schedule. The aim of this study was to advance in understanding the regulation mechanisms of stomach digestion and pattern of acid secretion in teleost fish. We have examined the postprandial pattern of gastric pH, pepsin activity, and mRNA expression for pepsinogen and proton pump in white seabream juveniles maintained under a light/dark 12/12 hours cycle and receiving only one morning meal. The pepsin activity was analyzed according to the standard protocol buffering at pH 2 and using the actual pH measured in the stomach. The results show how the enzyme precursor is permanently available while the hydrochloric acid, which activates the zymogen fraction, is secreted just after the ingestion of food. Results also reveal that analytical protocol at pH 2 notably overestimates true pepsin activity in fish stomach. The expression of the mRNA encoding pepsinogen and proton pump exhibited almost parallel patterns, with notable increases during the darkness period and sharp decreases just before the morning meal. These results indicate that white seabream uses the resting hours for recovering the mRNA stock that will be quickly used during the feeding process. Our data clearly shows that both daily illumination pattern and feeding time are involved at different level in the regulation of the secretion of digestive juices.

| S-EPMC3309002 | biostudies-literature

The inhibition of pepsin-catalysed reactions by products and product analogues. Kinetic evidence for ordered release of products.

Project description:1. The inhibition of pepsin-catalysed hydrolysis of N-acetyl-l-phenylalanyl-l-phenylalanylglycine by products and product analogues was studied. 2. The non-competitive nature of the inhibition by the product N-acetyl-l-phenylalanine confirms an ordered release of products, and points to a common mechanism (involving an amino-enzyme) for pepsin-catalysed transpeptidation and hydrolysis reactions. 3. N-Acetyl-l-phenylalanine ethyl ester is also a non-competitive inhibitor, but here the inhibition is of the ;dead-end' type. No ethanol is detectable in reaction mixtures, indicating that this ester cannot act as an amino group acceptor in a transpeptidation process. 4. The same is true for N-methanesulphonyl-l-phenylalanine methyl and methyl thiol esters. No methanethiol is liberated when the methyl thiol ester is present as an inhibitor of the hydrolytic reaction, and the hope that such a thiol ester would effectively trap the amino-enzyme was not fulfilled.

| S-EPMC1184643 | biostudies-other

Metal ion scavenging activity of elastin-like peptide analogues containing a cadmium ion binding sequence.

Project description:The development of simple and safe methods for recovering environmental pollutants, such as heavy metals, is needed for sustainable environmental management. Short elastin-like peptide (ELP) analogues conjugated with metal chelating agents are considered to be useful as metal sequestering agents as they are readily produced, environment friendly, and the metal binding domain can be selected based on any target metal of interest. Due to the temperature dependent self-assembly of ELP, the peptide-based sequestering agents can be transformed from the solution state into the particles that chelate metal ions, which can then be collected as precipitates. In this study, we developed a peptide-based sequestering agent, AADAAC-(FPGVG)4, by introducing the metal-binding sequence AADAAC on the N-terminus of a short ELP, (FPGVG)4. In turbidity measurements, AADAAC-(FPGVG)4 revealed strong self-assembling ability in the presence of metal ions such as Cd2+ and Zn2+. The results from colorimetric analysis indicated that AADAAC-(FPGVG)4 could capture Cd2+ and Zn2+. Furthermore, AADAAC-(FPGVG)4 that bound to metal ions could be readily recycled by treatment with acidic solution without compromising its metal binding affinity. The present study indicates that the fusion of the metal-binding sequence and ELP is a useful and powerful strategy to develop cost-effective heavy metal scavenging agents with low environmental impacts.

| S-EPMC8814041 | biostudies-literature

An active site peptide from pepsin C.

Project description:Porcine pepsin C is inactivated rapidly and irreversibly by diazoacetyl-dl-norleucine methyl ester in the presence of cupric ions at pH values above 4.5. The inactivation is specific in that complete inactivation accompanies the incorporation of 1mol of inhibitor residue/mol of enzyme and evidence has been obtained to suggest that the reaction occurs with an active site residue. The site of reaction is the beta-carboxyl group of an aspartic acid residue in the sequence Ile-Val-Asp-Thr. This sequence is identical with the active-site sequence in pepsin and the significance of this in terms of the different activities of the two enzymes is discussed.

| S-EPMC1176901 | biostudies-other

The purification and properties of a single chicken pepsinogen fraction and the pepsin derived from it.

Project description:1. Evidence is given for the presence of at least five pepsinogens in a crude extract of mixed chicken stomachs. One of these was purified and could be activated to yield a single pepsin. 2. The molecular weights of the pepsinogen and pepsin were 36000 and 34000 respectively. The pepsin associated at low pH values and low ionic strength. 3. The amino acid analyses of both proteins are given. The pepsin was devoid of phosphate but contained carbohydrate. 4. The N-terminal amino acids of pepsinogen and pepsin were serine and threonine respectively. Five amino acids were released by carboxypeptidase A and it was deduced that serine may be the C-terminal one. 5. Each protein contained one thiol group per molecule as determined by titration with p-chloromercuribenzoate. The rate of the reaction was very rapid with pepsin, but much slower with pepsinogen, although the same group appeared to react in both instances. The enzymic activity of pepsin was unaffected by the modification. 6. The isoionic point of the pepsin was close to pH4.0 and the enzyme was stable for long periods at pH values up to 7.0. 7. The enzyme hydrolysed bisphenyl sulphite almost as rapidly as did pig pepsin A.

| S-EPMC1177675 | biostudies-other

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