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Food & Function Dec 2021The activity of pepsin, the gastric protease, is generally considered to be negligible for pH ≥ 4, based on the results obtained with a few purified globular proteins....
The activity of pepsin, the gastric protease, is generally considered to be negligible for pH ≥ 4, based on the results obtained with a few purified globular proteins. The present study aimed at studying the activity of porcine pepsin on egg white proteins (EWP) and casein micelle micro-aggregates (CA) over a broad range of pH (from 1 to 7) for short (3 min) and long (2 h) digestion times. For a short time, the results confirmed a tendency for a higher rate of hydrolysis with decreasing pH, but with different pH activity profiles for both the substrates. More remarkably, the degree of hydrolysis of CA after 2 h of digestion was constant from pH 1 to pH 5, and was only reduced by half at pH 6. This finding demonstrates that pepsin can hydrolyse caseins from the very beginning of gastric digestion. Interestingly, the trend of the reaction kinetics over 2 h appeared to be rather characteristic of the type of the substrate and was largely independent in terms of pH. Most hydrolysis profiles could be accurately fitted by a power law, an empirical model that was then successfully applied to the static gastric proteolysis of 6 other food matrices. Overall, our results support the idea that pepsin activity under weakly acidic conditions (pH ≥ 4) should not always be neglected, in particular, for milk caseins, and that pepsin reaction kinetics during static gastric digestion seems to evolve proportionally to the power of the digestion time.
Topics: Animals; Caseins; Digestion; Egg Proteins; Hydrogen-Ion Concentration; Hydrolysis; In Vitro Techniques; Pepsin A; Proteolysis; Swine
PubMed: 34788782
DOI: 10.1039/d1fo02453a -
Pharmaceutical Research Jan 2024The purpose of the present study was to investigate the effect of food viscosity on the dissolution rate of a drug. There are two types of viscosity, macroviscosity and...
PURPOSE
The purpose of the present study was to investigate the effect of food viscosity on the dissolution rate of a drug. There are two types of viscosity, macroviscosity and microviscosity. Macroviscosity affects the diffusion layer thickness, whereas microviscosity affects the molecular diffusion coefficient. The mass transfer coefficient (k) in the intrinsic dissolution rate (IDR) depends on the viscosity (η) as k ∝ η (a is an exponent on η). In theory, for rotating flow over a disk, if a thickener increases only macroviscosity, a = -1/6, and if it increases both macroviscosity and microviscosity equally, a = -7/6.
METHOD
Benzocaine was used as a model drug. Hydroxypropyl cellulose (HPC) and methylcellulose (MC) were employed as control thickeners that increase only macroviscosity. Sucrose was employed as a control thickener for both macroviscosity and microviscosity. The FDA breakfast homogenate (BFH) was diluted with distilled water or 1 mM HCl with/without pepsin digestion. The IDR value was measured by the paddle-over-disk method.
RESULTS
The η value of 30% BFH distilled water was 209 mPa∙s, about 300 times higher than distilled water. It was further increased by HCl (430 mPa∙s), and reduced by pepsin digestion (35 mPa∙s). The k value was little affected by BFH (a = 0.00 to -0.09), slightly less than those in HPC (a = -0.19) and MC (a = -0.21). Sucrose decreased the k value more significantly (a = -0.70).
CONCLUSION
The IDR and k values of benzocaine were little affected by BFH, suggesting that BFH increased only macroviscosity.
Topics: Drug Liberation; Benzocaine; Viscosity; Pepsin A; Methylcellulose; Water; Sucrose
PubMed: 37884679
DOI: 10.1007/s11095-023-03620-y -
Journal of the American Society For... Sep 2021Hydrogen/deuterium exchange with mass spectrometry (HDX-MS) is a widely used technique to probe protein structural dynamics, track conformational changes, and map...
Hydrogen/deuterium exchange with mass spectrometry (HDX-MS) is a widely used technique to probe protein structural dynamics, track conformational changes, and map protein-protein interactions. Most HDX-MS studies employ a bottom-up approach utilizing the acid active protease pepsin to digest the protein of interest, often utilizing immobilized protease in a column format. The extent of proteolytic cleavage will greatly influence data quality and presents a major source of variation in HDX-MS studies. Here, we present a simple cocktail of commonly available peptides that are substrates of pepsin and can serve as a rapid check of pepsin column activity. The peptide-based assay requires no system modifications and provides an immediate readout to check and benchmark pepsin activity across different HDX-MS platforms.
Topics: Animals; Chromatography, Liquid; Enzymes, Immobilized; Hydrogen Deuterium Exchange-Mass Spectrometry; Pepsin A; Peptide Fragments; Protein Conformation; Proteins; Reproducibility of Results; Swine
PubMed: 33984240
DOI: 10.1021/jasms.1c00080 -
International Journal of Biological... Feb 2023The ability of a therapeutic compound to bind to proteins is critical for characterizing its therapeutic impacts. We have selected quercetin (Qu), a most common...
The ability of a therapeutic compound to bind to proteins is critical for characterizing its therapeutic impacts. We have selected quercetin (Qu), a most common flavonoid found in plants and vegetables among therapeutic molecules that are known to have anti-inflammatory, antioxidant, anti-genotoxic, and anti-cancer effects. The current study aimed to see how quercetin interacts with pepsin in an aqueous environment under physiological conditions. Absorbance and emission spectroscopy, circular dichroism (CD), and kinetic methods, as well as molecular dynamic (MD) simulation and docking, were applied to study the effects of Qu on the structure, dynamics, and kinetics of pepsin. Stern-Volmer (K) constants were computed for the pepsin-quercetin complex at three temperatures, showing that Qu reduces enzyme emission spectra using a static quenching. With Qu binding, the V and the k/K values decreased. UV-vis absorption spectra, fluorescence emission spectroscopy, and CD result indicated that Qu binding to pepsin leads to microenvironmental changes around the enzyme, which can alter the enzyme's secondary structure. Therefore, quercetin caused alterations in the function and structure of pepsin. Thermodynamic parameters, MD binding, and docking simulation analysis showed that non-covalent reactions, including the hydrophobic forces, played a key role in the interaction of Qu with pepsin. The findings conclude of spectroscopic experiments were supported by molecular dynamics simulations and molecular docking results.
Topics: Molecular Dynamics Simulation; Quercetin; Pepsin A; Molecular Docking Simulation; Binding Sites; Circular Dichroism; Spectrometry, Fluorescence; Thermodynamics; Protein Binding
PubMed: 36464189
DOI: 10.1016/j.ijbiomac.2022.11.296 -
HNO Nov 2021Laryngopharyngeal reflux (LPR) is defined as backflow of gastral or gastroduodenal content into the upper aerodigestive tract and characterized by a variety of... (Review)
Review
Laryngopharyngeal reflux (LPR) is defined as backflow of gastral or gastroduodenal content into the upper aerodigestive tract and characterized by a variety of unspecific symptoms such as chronic cough, globus sensation, or mucus hypersecretion. Due to the lack of a gold standard and the heterogeneity of studies, the diagnosis of LPR is still problematic and challenging. However, in patients with characteristic symptoms and endoscopic findings, with an increased reflux symptom index, a pathologic reflux finding score (RFS), pathologic 24 h esophageal or oropharyngeal pH monitoring, and without any other underlying condition, the diagnosis of LPR is probable. In the following review, we critically discuss the abovementioned methods as well as more recent tools such as measurements of pepsin concentrations in the saliva for diagnosis of LPR.
Topics: Esophageal pH Monitoring; Humans; Laryngopharyngeal Reflux; Pepsin A; Saliva
PubMed: 33619606
DOI: 10.1007/s00106-021-01006-3 -
Lin Chuang Er Bi Yan Hou Tou Jing Wai... Apr 2018Laryngeal carcinoma is a common malignancy, and the incidence of this disease is on the rise. In recent years, more and more studies of the etiology and risk factors... (Review)
Review
Laryngeal carcinoma is a common malignancy, and the incidence of this disease is on the rise. In recent years, more and more studies of the etiology and risk factors have confirmed the correlation between laryngopharygeal reflux and the incidence of laryngeal carcinoma. Laryngopharygeal reflux is defined as reflux of the stomach contents above the upper esophageal sphincter. Stimulation and injury of acid to the esophagus and throat mucosa have now been studied more thoroughly, and pepsin plays an increasingly important role in laryngopharygeal reflux disease. The incidence of laryngopharygeal reflux in patients with laryngeal carcinoma reported in the literature was 54.0%-88.7%, mainly because of mucosal injury due to the combined effect of gastric acid and pepsin. This article reviews the significance of pepsin in laryngopharygeal reflux, its mechanism of action and related clinical detection methods.
Topics: Gastroesophageal Reflux; Humans; Laryngeal Neoplasms; Mucous Membrane; Pepsin A
PubMed: 29798094
DOI: 10.13201/j.issn.1001-1781.2018.07.022 -
Enzyme and Microbial Technology Nov 2020Pepsin, the archetypal pepsin-like aspartic protease, is irreversibly denatured when exposed to neutral pH conditions whereas renin, a structural homologue of pepsin, is... (Comparative Study)
Comparative Study
Pepsin, the archetypal pepsin-like aspartic protease, is irreversibly denatured when exposed to neutral pH conditions whereas renin, a structural homologue of pepsin, is fully stable and optimally active in the same conditions despite sharing highly similar enzyme architecture. To gain insight into the structural determinants of differential aspartic protease pH stability, the present study used comparative bioinformatic and structural analyses. In pepsin, an abundance of polar and aspartic acid residues were identified, a common trait with other acid-stable enzymes. Conversely, renin was shown to have increased levels of basic amino acids. In both pepsin and renin, the solvent exposure of these charged groups was high. Having similar overall acidic residue content, the solvent-exposed basic residues may allow for extensive salt bridge formation in renin, whereas in pepsin, these residues are protonated and serve to form stabilizing hydrogen bonds at low pH. Relative differences in structure and sequence in the turn and joint regions of the β-barrel and ψ-loop in both the N- and C-terminal lobes were identified as regions of interest in defining divergent pH stability. Compared to the structural rigidity of renin, pepsin has more instability associated with the N-terminus, specifically the B/C connector. By contrast, renin exhibits greater C-terminal instability in turn and connector regions. Overall, flexibility differences in connector regions, and amino acid composition, particularly in turn and joint regions of the β-barrel and ψ-loops, likely play defining roles in determining pH stability for renin and pepsin.
Topics: Amino Acid Sequence; Amino Acids; Animals; Computational Biology; Enzyme Stability; Humans; Hydrogen Bonding; Hydrogen-Ion Concentration; Pepsin A; Protein Structure, Tertiary; Protein Unfolding; Renin; Sequence Alignment; Solvents
PubMed: 33051007
DOI: 10.1016/j.enzmictec.2020.109632 -
Journal of Trace Elements in Medicine... Jul 2021The paper presents a study on the influence of different lithium carbonate and lithium citrate concentration on proteolytic enzymes, namely pepsin and trypsin, in vitro....
BACKGROUND
The paper presents a study on the influence of different lithium carbonate and lithium citrate concentration on proteolytic enzymes, namely pepsin and trypsin, in vitro. Lithium can directly affect enzyme activity. Its influence on many bodily functions in both ill and healthy people has been proven.
METHODS
To assess the influence of Li ions concentration and the substrate/enzyme ratio on pepsin and trypsin activity in vitro, 60 factorial experiments were conducted (each repeated 30 times).
MAIN FINDINGS
For both enzymes, statistically significant changes in their activity under the influence of lihium carbonate and lithium citrate were observed. The biggest increase in enzyme activity reached even 198.6 % and the largest decrease in enzyme activity reached about 50 %.
CONCLUSIONS
The study shows that both organic and inorganic forms of lithium salts cause changes in the activity of digestive enzymes. Different concentrations of lithium carbonate and lithium citrate stimulate or inhibit the activity of trypsin and pepsin.
Topics: Citrates; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; Ions; Lithium Carbonate; Pepsin A; Trypsin
PubMed: 33915410
DOI: 10.1016/j.jtemb.2021.126763 -
Medicine May 2021The aim of this study is to explore the relationship between gastroesophageal reflux disease (GERD) and vocal fold polyps (VFPs).This is a Case-Control study and was... (Observational Study)
Observational Study
The aim of this study is to explore the relationship between gastroesophageal reflux disease (GERD) and vocal fold polyps (VFPs).This is a Case-Control study and was performed with the help of The Second Affiliated Hospital of Chongqing Medical University.Twenty-seven patients with VFP and 20 controls without VFP were recruited between May and October 2018. All the subjects underwent a saliva pepsin test, completed the GerdQ questionnaire and 24-hour multichannel intraluminal impedance with pH (24-h MII-pH) monitoring. Twenty-five resected VFP specimens were examined with immunohistochemical (IHC) and double immunofluorescence (IF) staining.The incidence of GERD in the VFP group was significantly higher than that in the control group (P = .003). Patients with VFP had significantly higher GerdQ scores, pepsin concentrations, and pepsin-positive rates (P < .05). Moreover, the number of proximal and upright reflux events was significantly higher in the VFP group (P < .05). The pepsin concentration in saliva showed a significant positive correlation with the pepsin levels in tissues (r2 = 0.50, P = .011). Pepsin and TGF-β1-positive cells were colocalized with CD45RO-positive cells. IHC staining showed that the majority of VFP patients had a positive expression of pepsin (20/25, 80%) and pepsin-positive cells were found in both the squamous epithelium and mesenchymal tissues. IHC staining of TGF-β1 in VFP revealed findings similar to those of pepsin staining.GERD is an important risk factor for VFP. Pepsin may promote the aggregation of immune cells, increase the local cytokines, and promote inflammatory reaction, suggesting a potential new pathogenesis for VFP. The saliva pepsin test is a reliable method for GERD diagnosis.
Topics: Adult; Aged; Case-Control Studies; Esophageal pH Monitoring; Female; Gastroesophageal Reflux; Humans; Incidence; Male; Middle Aged; Pepsin A; Polyps; Prospective Studies; Respiratory Mucosa; Risk Factors; Saliva; Vocal Cords
PubMed: 34011039
DOI: 10.1097/MD.0000000000025787 -
Luminescence : the Journal of... Sep 2019In this paper, the interactions of pepsin with fluoroquinolones, including norfloxacin (NFX) or ofloxacin (OFX), were investigated using fluorescence spectroscopy. The...
In this paper, the interactions of pepsin with fluoroquinolones, including norfloxacin (NFX) or ofloxacin (OFX), were investigated using fluorescence spectroscopy. The effects of NFX or OFX on pepsin showed that the molecular conformation of pepsin and the microenvironment of tryptophan residues were changed under mimicked physiological conditions. Static quenching was suggested as a factor. Quenching constants and binding constants were determined and thermodynamic parameters were calculated at three temperatures (25°C, 31°C and 37°C). Molecular interaction distances (binding distance r) were obtained. Binding was enthalpy driven and the process was spontaneous. Synchronous fluorescence, three-dimensional fluorescence spectroscopy and molecular simulation were used for analysis. Interactions were further tested using molecular modelling. Quenching and binding constants of NFX with pepsin were the highest when testing NFX/OFX/fleroxacin/gatifloxacin with pepsin combinations. NFX was the strongest quencher, and affinity of NFX for pepsin was higher than that of OFX/fleroxacin/gatifloxacin.
Topics: Anti-Bacterial Agents; Fleroxacin; Fluorescence; Fluoroquinolones; Kinetics; Molecular Conformation; Molecular Docking Simulation; Norfloxacin; Pepsin A; Protein Binding; Spectrometry, Fluorescence
PubMed: 31074200
DOI: 10.1002/bio.3642