[en] The structure of porcine pepsin crystallized in the presence of dimethyl sulphoxide has been analysed by X-ray crystallography to obtain insights into the structural events that occur at the onset of chemical denaturation of proteins. The results show that one dimethyl sulphoxide molecule occupies a site on the surface of pepsin interacting with two of its residues. An increase in the average temperature factor of pepsin in the presence of dimethyl sulphoxide has been observed indicating protein destabilization induced by the denaturant. Significant increase in the temperature factor and weakening of the electron density have been observed for the catalytic water molecule located between the active aspartates. The conformation of pepsin remains unchanged in the crystal structure. However, the enzyme assay and circular dichroism studies indicate that dimethyl sulphoxide causes a slight change in the secondary structure and complete loss of activity of pepsin in solution

[en] The ph dependence of the size of the enzyme pepsin is investigated in aqueous medium via molecular dynamics simulations at ambient conditions. The ph value may influence both the pepsin charge and its structure at microscopic level. This investigation allows to understand the volume compatibility between pepsin and the pores size in meso porous materials, which is a relevant issue for the production of hybrid bio-inorganic composite where a bio catalyst is encapsulated in porous inorganic matrices. The results obtained by means of simulation techniques indicate that the average pepsin dimensions along its inertia axes are consistent with the microporous silica Sba-15 pore diameter. The present study indicates that, while the total charge of the bio macromolecule varies along with the enzyme residues protonation state, there is no evidence of significant ph-induced protein size modification.

[en] The determination of serum pepsinogen A (=pepsinogen I) levels is of clinical importance in the study of duodenal ulcer, atrophic gastritis and gastric cancer. In the present study two different quantitative immunological techniques for serum pepsinogen A were compared: a radioimmunoassay (RIA) (Helsinki) and an enzyme-linked immunosorbent assay (ELISA) (Amsterdam). Serum samples of 177 subjects with various gastric diseases were tested in a double blind study. The correlation was excellent (r=0.954 in the range 0-760 μg/l and r=0.971 in the range 0-100 μg/l). The functional relationship between ELISA (x) and RIA (y), determined by weighted model II regression, was y=1.12x-0.54. Initially the use of goat anti-PGA in the ELISA resulted in falsely high values in about 10% of the individuals. This was caused by circulating antibodies cross-reacting with goat IgG. This artefact was eliminated by pre-incubation of all samples with non-immune goat serum. (author)

[en] Semen cassiae tea is a functional beverage, which is commonly drunk as a kind of roasted tea in Korea and China. This study was performed to characterize the binding mechanism of aurantio-obtusin, a major bio-activity compound of semen cassiae tea, with pepsin by experimental and theoretical methods. Steady-state and time-resolved fluorescence experiments showed that binding of aurantio-obtusin with pepsin occurred through static quenching mechanism. The binding mode was displayed using molecular simulation, which suggested that the binding process was spontaneous and might involved hydrophobic and hydrogen bonding forces. Three-dimensional fluorescence, FTIR, and Circular dichroism data further confirmed the secondary structure changes in pepsin upon aurantio-obtusin. This study may provide theoretical basis for its application in pharmaceutics and clinic.

[en] The antimicrobial activity of tissue engineering scaffolds is crucial for successful implantations and surgeries by reducing surgical infections. In this study, small intestinal submucosa (SIS) extracts were prepared by in vitro pepsin digestion (pSIS) and its antimicrobial active is stronger than those prepared by accelerated hydrolysis (aSIS). Compared with aSIS, the average molecular weight of pSIS seems smaller with more narrow distribution via SDS-PAGE electrophoresis combined with commassie blue staining. Furthermore, pSIS coated porous type I collagen scaffold (pSIS/COL I scaffolds) displayed a strong antibacterial activity and is suitable for cell seeded and growth, indicating that it can be potentially applied to tissue engineering or surgical tissue repairing in the future. (paper)

[en] Herein, the interaction between gliclazide (GCZ) and pepsin (PEP) was explored under simulated physiological conditions by multiple spectroscopy methods and molecular docking. The results showed that a new complex of 1:1 was formed between GCZ and PEP, thereby quenching the endogenous fluorescence of PEP. The addition of GCZ changed the conformation of PEP and increased the α-helix content in PEP from 20.16% to 21.13%. Using the binding constant K_a of the reaction between GCZ and PEP and the number of binding sites n, the binding rate formulas of GCZ and PEP were deduced. It was estimated that when the patient takes 40 mg of GCZ, the PEP in the gastric juice will be reduced by 96.69%. That meant taking GCZ will seriously affect the patient's digestive function. The results of molecular docking indicated that the GCZ binding site was located in the active center of PEP. The interaction of the two was driven by electrostatic attraction and hydrogen bonding forces.

[en] Reovirus is an enteric virus comprising eight structural proteins that form a double-layered capsid. During reovirus entry into cells, the outermost capsid layer (composed of proteins σ3 and μ1C) is proteolytically processed to generate an infectious subviral particle (ISVP) that is subsequently uncoated to produce the transcriptionally active core particle. Kinetic studies suggest that protein σ3 is rapidly removed from virus particles and then protein μ1C is cleaved. Initial cleavage of μ1C has been well described and generates an amino (N)-terminal δ peptide and a carboxyl (C)-terminal phi peptide. However, cleavage and removal of σ3 is an extremely rapid event that has not been well defined. We have treated purified reovirus serotype 1 Lang virions with a variety of endoproteases. Time-course digestions with chymotrypsin, Glu-C, pepsin, and trypsin resulted in the initial generation of two peptides that were resolved in SDS-PAGE and analyzed by in-gel tryptic digestion and MALDI-Qq-TOFMS. Most tested proteases cut σ3 within a 'hypersensitive' region between amino acids 217 and 238. In addition, to gain a better understanding of the sequence of subsequent proteolytic events that result in generation of reovirus subviral particles, time-course digestions of purified particles were performed under physiologic salt conditions and released peptide fragments ranging from 500 to 5000 Da were directly analyzed by MALDI-Qq-TOFMS. Trypsin digestion initially released a peptide that corresponded to the C-terminus of μ1C, followed by a peptide that corresponded to amino acids 214-236 of the σ3 protein. Other regions of μ1C were not observed until protein σ3 was completely digested. Similar experiments with Glu-C indicated the hypersensitive region of σ3 was cut first when virions were treated at pH values of 4.5 or 7.4, but treatment of virions with pepsin at pH 3.0 released different σ3 peptides, suggesting acid-induced conformational changes in this outer capsid protein. These studies also revealed that the N-terminus of σ3 is acetylated

[en] In this study we have investigated the chemical-physical and morphological properties of intact and atelocollagen sponges used for tissue engineering. The porous sponges were prepared by lyophilization and their physico-chemical characteristics (water binding capacity, denaturing temperature, amino group content) were investigated. Considering the importance of the 'in vivo' interactions between these sponges and the tissue, our attention was addressed (a) to clarify the relationships between the morphology and the amount of water absorbed and (b) to evaluate the influence of pepsin-alkaline treatment on the reorganization of the atelocollagen fibres. Conventional scanning electron microscopy (SEM) and environmental scanning electron microscopy (ESEM) were employed to study the morphology and wetting behaviour of the intact and atelocollagen sponges. The observations by SEM indicated remarkable differences both in the structure and dimension of the pores between intact and atelocollagen sponges. At the data are related to a different water binding capacity. However, the ESEM observations, achieved by changing the relative humidity in the operative chamber, demonstrated that the water adsorbed can be removed with major difficulty from atelocollagen sponges than from intact ones

No abstract available

[en] Pork is known as an allergenic food with porcine serum albumin (PSA, 66 kDa) representing the major allergen. This study was conducted to investigate the change in antigenicity of PSA in gamma-irradiated sausage extract treated with pepsin and trypsin. Sausage products (A and B) were irradiated at 1, 3, 10, and 20 kGy. After irradiation, sausage proteins were extracted and digested with pepsin (1:200, 30 min) and trypsin (1:300, 5, 30, 60, 90, and 120 min). The binding ability of PSA in extracts of the irradiated sausages (A and B) decreased by over 3 kGy relative to the binding ability of PSA in extracts of intact sausages and showed no notable differences when the dose of radiation ranged from 3 to 20 kGy. After treatment with pepsin and trypsin, the binding ability of PSA in extracts of the irradiated sausages was decreased more relative to that of intact sausages and showed no significant differences when the period of trypsin treatment is increased or when the dose of irradiation is increased. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that there was no visible change in the intensity of the PSA band in extracts of the irradiated sausages. After pepsin and trypsin treatment, the intensity of PSA band faded with increasing doses of irradiation. In conclusion, antigenicity of PSA in pork sausages could be reduced by gamma irradiation. - Highlights: → Change in antigenicity of PSA in irradiated sausage extract (ISE) was examined. → Binding ability of PSA in ISE was decreased compared to intact extract. → Binding ability of PSA in ISE after enzyme treatments was also further decreased. → Intensity of PSA band in ISE after enzyme treatments became weak.