[20] The porcine pepsins and pepsinogens

Gastrobodies are engineered antibody mimetics resilient to pepsin and hydrochloric acid

Protein-based targeting reagents, such as antibodies and non-antibody scaffold proteins, are rapidly inactivated in the upper gastrointestinal (GI) tract. Hydrochloric acid in gastric juice denatures proteins and activates pepsin, concentrations of which reach 1 mg/mL in the mammalian stomach. Two stable scaffold proteins (nanobody and nanofitin), previously developed to be protease-resistant, were completely digested in less than 10 min at 100-fold lower concentration of pepsin than found in the stomach. Here we present gastrobodies, a protein scaffold derived from Kunitz soybean trypsin inhibitor (SBTI). SBTI is highly resistant to the challenges of the upper GI tract, including digestive proteases, pH 2 and bile acids. Computational prediction of SBTI's evolvability identified two nearby loops for randomization, to create a potential recognition surface which was experimentally validated by alanine scanning. We established display of SBTI on full-length pIII of M13 phage. Phage selection of gastrobody libraries against the glucosyltransferase domain of Clostridium difficile toxin B (GTD) identified hits with nanomolar affinity and enzyme inhibitory activity. Anti-GTD binders retained high stability to acid, digestive proteases and heat. Gastrobodies show resilience to exceptionally harsh conditions, which should provide a foundation for targeting and modulating function within the GI tract.

Refinement strategy for antivenom preparation of high yield and quality

Antivenoms from hyperimmune animal plasma are the only specific pharmaceuticals against snakebites. The improvement of downstream processing strategies is of great interest, not only in terms of purity profile, but also from yield-to-cost perspective and rational use of plasma of animal origin. We report on development of an efficient refinement strategy for F(ab')2-based antivenom preparation. Process design was driven by the imperative to keep the active principle constantly in solution as a precautionary measure to preserve stability of its conformation (precipitation of active principle or its adsorption to chromatographic stationary phase has been completely avoided). IgG was extracted from hyperimmune horse plasma by 2% (V/V) caprylic acid, depleted from traces of precipitating agent and digested by pepsin. Balance between incomplete IgG fraction breakdown, F(ab')2 over-digestion and loss of the active principle's protective efficacy was achieved by adjusting pepsin to substrate ratio at the value of 4:300 (w/w), setting pH to 3.2 and incubation period to 1.5 h. Final polishing was accomplished by a combination of diafiltration and flow-through chromatography. Developed manufacturing strategy gave 100% pure and aggregate-free F(ab')2 preparation, as shown by size-exclusion HPLC and confirmed by MS/MS. The overall yield of 75% or higher compares favorably to others so far reported. This optimised procedure looks also promising for large-scale production of therapeutic antivenoms, since high yield of the active drug and fulfillment of the regulatory demand considering purity was achieved. The recovery of the active substance was precisely determined in each purification step enabling accurate estimation of the process cost-effectiveness.

Chicken and rabbit antibodies against porcine pepsinogen A

Isolated porcine pepsinogen A was used for the preparation of polyclonal rabbit and polyclonal chicken anti-pepsinogen A antibodies. Immunochemical properties of both immunoglobulin fractions were compared. The rabbit anti-serum was further purified using immobilized porcine pepsinogen A on magnetic cellulose beads and the resulting anti-pepsinogen A fraction proved to be applicable for the separation and the determination of porcine pepsinogen A. In contrary, antibodies prepared from chicken eggs by the same way have been found not suitable for the evaluation of the pepsinogen A level. Unexpectedly, the pre-immune fraction of chicken antibodies showed reactivity against porcine pepsinogen A and the affinity separation of specific polyclonal chicken anti-pepsinogen A antibodies on immobilized porcine pepsinogen A did not result in an enrichment of anti-pepsinogen A antibodies.

Slow-tight binding inhibition of pepsin by an aspartic protease inhibitor from Streptomyces sp. MBR04

The present article reports a low molecular weight aspartic protease inhibitor from a Streptomyces sp. MBR04 exhibiting a two-step inhibition mechanism against pepsin. The kinetic interactions revealed a reversible, competitive, slow-tight binding inhibition with an IC(50) and K(i) values of 4.5 nM and 4 nM respectively. The conformational changes induced upon inhibitor binding to pepsin was monitored by far and near UV analysis, demonstrated that the inhibitor binds to the active site and causes inactivation. Chemical modification of the inhibitor with WRK and TNBS abolished the antiproteolytic activity of the inhibitor.

Distribution of pepsinogen- and ghrelin-producing cells in the digestive tract of Japanese eel (Anguilla japonica) during metamorphosis and the adult stage

Pepsinogen is the precursor form of the gastric-specific digestive enzyme, pepsin. Ghrelin is a representative gastric hormone with multiple functions in vertebrates, including the regulation of growth hormone release, stimulation of food intake and gastrointestinal motility function. We investigated chronological changes in the distribution of pepsinogen-expressing cells by in situ hybridization and ghrelin-immunoreactive cells by immunohistochemistry in the Japanese eel (Anguilla japonica) during metamorphosis from the leptocephalus sage to the elver stage. The ghrelin-producing cells first appeared in the gastric cecum and pyloric portion of the stomach in the late phase of metamorphosing leptocephali, whereas the pepsinogen-producing cells were first detected in the early phase of the glass-eel stage. These suggest that endocrine cells differentiated earlier than exocrine cells in the eel stomach. Accompanying eel development, the distribution of ghrelin-producing cells spread to the esophagus and other regions of the stomach, but not to the intestine. These results may be related to the changes in dietary habits during metamorphosis in the Japanese eel.

Obtaining antimicrobial peptides by controlled peptic hydrolysis of bovine hemoglobin

Under standard conditions, the peptides and specially the active peptides were obtained from either the denatured hemoglobin that all structures are completely modified or either the native hemoglobin where all structures are intact. In these conditions, antibacterial peptides were isolated from a very complex peptidic hydrolysate which contains more than one hundred peptides having various sizes and characteristics, involving a complex purification process. The new hydrolysis conditions were obtained by using 40% methanol, 30% ethanol, 20% propanol or 10% butanol. These conditions, where only the secondary structure of hemoglobin retains intact, were followed in order to enrich the hydrolyzed hemoglobin by active peptides or obtain new antibacterial peptides. In these controlled peptic hydrolysis of hemoglobin, a selective and restrictive hydrolysate contained only 29 peptides was obtained. 26 peptides have an antibacterial activity against Micrococcus luteus, Listeria innocua, and Escherichia coli with MIC from 187.1 to 1 μM. Among these peptides, 13 new antibacterial peptides are obtained only in these new hydrolysis conditions.

The biochemical and functional food properties of the bowman-birk inhibitor

The Bowman-Birk inhibitor (BBI) is a small water-soluble protein present in soybean and almost all monocotyledonous and dicotyledonous seeds. The molecular size of BBI ranges from 1,513 Da to about 20,000 Da. BBI is to seeds what alpha(1)-antitrypsin is to humans. Soy-based food products rich in BBI include soybean grits, soymilk, oilcake, soybean isolate, and soybean protein concentrate. BBI is stable within the pH range encountered in most foods, can withstand boiling water temperature for 10 min, resistant to the pH range and proteolytic enzymes of the gastrointestinal tract, bioavailable, and not allergenic. BBI reduces the proteolytic activities of trypsin, chymotrypsin, elastase, cathepsin G, and chymase, serine protease-dependent matrix metalloproteinases, urokinase protein activator, mitogen activated protein kinase, and PI3 kinase, and upregulates connexin 43 (Cx43) expression. Several studies have demonstrated the efficacy of BBI against tumor cells in vitro, animal models, and human phase IIa clinical trials. FDA considers BBI as a drug. In 1999, FDA allowed a health claim on food labels stating that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease [corrected] This review highlights the biochemical and functional food properties of the Bowman-Birk inhibitor.

Biochemical characterization of a low molecular weight aspartic protease inhibitor from thermo-tolerant Bacillus licheniformis: Kinetic interactions with Pepsin

The present article reports a low molecular weight aspartic protease inhibitor, API, from a newly isolated thermo-tolerant Bacillus licheniformis. The inhibitor was purified to homogeneity as shown by rp-HPLC and SDS-PAGE. API is found to be stable over a broad pH range of 2-11 and at temperature 90 degrees C for 2 1/2h. It has a Mr (relative molecular mass) of 1363 Da as shown by MALDI-TOF spectra and 1358 Da as analyzed by SDS-PAGE . The amino acid analysis of the peptide shows the presence of 12 amino acid residues having Mr of 1425 Da. The secondary structure of API as analyzed by the CD spectra showed 7% alpha-helix, 49% beta-sheet and 44% aperiodic structure. The Kinetic studies of Pepsin-API interactions reveal that API is a slow-tight binding competitive inhibitor with the IC(50) and Ki values 4.0 nM and (3.83 nM-5.31 nM) respectively. The overall inhibition constant Ki* value is 0.107+/-0.015 nM. The progress curves are time-dependent and consistent with slow-tight binding inhibition: E+I -->/<-- (k(4), k(5)) EI -->/<-- (k(6), k(7)) EI*. Rate constant k(6)=2.73+/-0.32 s(-1) reveals a fast isomerization of enzyme-inhibitor complex and very slow dissociation as proved by k(7)=0.068+/-0.009 s(-1). The Rate constants from the intrinsic tryptophanyl fluorescence data is in agreement with those obtained from the kinetic analysis; therefore, the induced conformational changes were correlated to the isomerization of EI to EI*.

Rodent monophyly deduced from the unique gastric proteinase constitution and molecular phylogenetic analyses using pepsinogen-C cDNA sequences

Pepsinogens are zymogens of pepsins, the gastric digestive proteinases. Although pepsinogen A is predominant in most mammalian species hitherto known, pepsinogen C is expressed exclusively and the lack of pepsinogen A is evidenced in the rat and guinea pig. Furthermore, in these two rodents, considerable amount of procathepsin E is also expressed in gastric mucosa although it is almost undetectable in other mammals. In this paper, in order to clarify whether such unique gastric proteinase constitution is common among rodents, we carried out purification and characterization of gastric proteinases, and molecular cloning of pepsinogen-C cDNAs from several rodent species including the degu and coypu. Pepsinogen C and procathepsin E were isolated but pepsinogen A was undetectable in the rodents, leading to the conclusion that that rodents commonly share the unique gastric proteinase constitution. This feature could be treated as a new "molecular synapomorphy", supporting strongly monophyly of the order Rodentia. From the molecular phylogenetic analyses of pepsinogen-C cDNA sequences, monophyly of the order Rodentia was also supported by the analyses with high statistic reliabilities.

Effect of pepsin digestion on the antivenom activity of equine immunoglobulins

Enzyme digestion of animal-derived sera followed by antibody purification is a classical process used to prepare snake antivenoms worldwide. In this work, we have studied the effect of the harsh conditions prevailing during the digestion step on the activity of the final product, F(ab')(2). To this purpose, the recovery of the activity of anti-Bothrops hyperimmune equine plasma was determined after pepsin digestion under different sets of processing conditions. The balance between pH level and reaction time was found to be critical, reflecting a compromise between complete cleavage of immunoglobulins and strong denaturation of the F(ab')(2) fragments. For pH in the range 2.8-3.2, 30-65% of the initial activity was lost depending mainly on the processing time, as determined by a competition ELISA technique. Pepsin digestion was also carried out with purified immunoglobulins from the same plasma. SDS PAGE run on the digested immunoglobulins allowed us to verify that the lightest isotypes were more resistant to digestion than the heavier ones. In conclusion, for equine F(ab')(2) antivenom production, it seems convenient to carry out digestion at pH values sufficiently low to ensure that total IgG breakdown is achieved in the shortest time compatible with precise operation in the production scale.

Identification of pepsinogen gene in the genome of stomachless fish, Takifugu rubripes

Pepsinogen is a precursor of pepsin, a gastric specific protease belonging to the aspartic proteinase family. In teleosts, several species, such as zebrafish and puffer, have independently lost gastric glands. So whether puffer have pepsinogen gene or not is an interesting issue. A search of GSS database for pufferfish, Takifugu rubripes, revealed five different aspartic proteinase genes in its genome. One of them (pPep) has typical pepsinogen structure and belongs to the fish pepsinogen cluster by phylogenic analysis. The pPep antisense probe hybridized to the gastric glands of flounder stomach. Therefore, we concluded that pPep is a pufferfish pepsinogen. The pufferfish pepsinogen mRNA was not expressed in the digestive organs but specifically in the skin. We speculated that while Tetraodontiformes evolutionarily lost gastric glands, pufferfish pepsinogen acquired an alternative function to food digestion.

Fractionation of equine antivenom using caprylic acid precipitation in combination with cationic ion-exchange chromatography

A combined process of caprylic acid (CA) precipitation and ion-exchange chromatography on SP-Sepharose was studied as a means to fractionate pepsin-digested horse antivenom F(ab')(2) antibody. In the CA precipitation, the optimal concentration for fractionation of F(ab')(2) from pepsin-digested horse plasma was 2%, in which 89.61% of F(ab')(2) antibody activity was recovered in the supernatant with 1.5-fold purification. A significant amount of pepsin was not precipitated and remained active under these conditions. An analytical cation exchanger Protein-Pak SP 8HR HPLC column was tested to establish optimal conditions for the effective separation of IgG, albumin, pepsin and CA from the F(ab')(2) product. From these results, the supernatant from CA precipitation of pepsin-digested plasma was subjected to a SP-Sepharose column chromatography using a linear salt gradient. With stepwise elution, a peak containing F(ab')(2) antibody could be obtained by elution with 0.25 M NaCl. The total recovery of antibody was 65.56% with 2.91-fold purification, which was higher than that achieved by ammonium sulfate precipitation. This process simultaneously and effectively removed residual pepsin, high molecular weight aggregates and CA in the final F(ab')(2) product, and should be suitable for large-scale fractionation of therapeutic equine antivenoms.

Primary structure, unique enzymatic properties, and molecular evolution of pepsinogen B and pepsin B

Purification of pepsinogen B from dog stomach was achieved. Activation of pepsinogen B to pepsin B is likely to proceed through a one-step pathway although the rate is very slow. Pepsin B hydrolyzes various peptides including beta-endorphin, insulin B chain, dynorphin A, and neurokinin A, with high specificity for the cleavage of the Phe-X bonds. The stability of pepsin B in alkaline pH is noteworthy, presumably due to its less acidic character. The complete primary structure of pepsinogen B was clarified for the first time through the molecular cloning of the respective cDNA. Molecular evolutional analyses show that pepsinogen B is not included in other known pepsinogen groups and constitutes an independent cluster in the consensus tree. Pepsinogen B might be a sister group of pepsinogen C and the divergence of these two zymogens seems to be the latest event of pepsinogen evolution.

Enhanced pepsin digestion: a novel process for purifying antibody F(ab')(2) fragments in high yield from serum

Enzyme-cleaved antibodies are used widely for the treatment of envenoming. Such products should comprise only 'highly pure' immunoglobulin fragments since Fc or other contaminating protein fragments or their aggregates may lead to side effects. The digestion of ovine antiserum and its purified IgG were investigated using pepsin and trypsin. Trypsin was effective at digesting purified IgG but unsuitable for the direct digestion of serum. In contrast, pepsin was highly effective at digesting all unwanted serum components to low molecular weight (< or =13 kDa) fragments while leaving the approximately 100-kDa F(ab')(2) intact. The optimum pH for pepsin digestion was between 3.25 and 3.50. The effects of salt concentration and pH on the digestion products were investigated by size exclusion chromatography under various conditions, which revealed a pH-dependent aggregation of some of the low molecular weight Fc and non-IgG fragments. These high molecular weight aggregates were not shown by SDS-PAGE. Unwanted low molecular weight fragments could be removed simply by diafiltration with a 30-kDa nominal molecular weight cutoff membrane and piperazine buffer (containing 150 mM NaCl, pH 6), leaving an F(ab')(2) solution contaminated only with some pepsin and a small amount of the aggregated low molecular weight fragments. These highly acidic contaminants were then removed easily using an anion exchange column and the F(ab')(2) produced following a subsequent concentration step was essentially free from pepsin and aggregates with a purity of over 96% and a yield of 19.3 g F(ab')(2)/l serum. This novel, high yield method for processing serum to highly pure F(ab')(2) avoids salt precipitation and centrifugation and should be suitable for large-scale production.

Purification and characterization of goat pepsinogens and pepsins

Three type-A and two type-C pepsinogens, namely, pepsinogens A-1, A-2, A-3, C-1, and C-2, were purified from adult goat abomasum. Their relative levels in abomasal mucosa were 27, 19, 14, 25, and 15%, respectively. Amino acid compositions were quite similar between isozymogens of respective types, but different between the two types especially in the Glx/Asx and Leu/Ile ratios. NH2-terminal amino acid sequences of pepsinogens A-3 and C-2 were SFFKIPLVKKKSLRQNLIEN- and LVKIPLKKFKSIRETM-, respectively. Pepsins A and C showed maximal hemoglobin-digestive activity at around pH 2 and 3, respectively, and specific activities of pepsins C were higher than those of pepsins A. Two subtypes of pepsin A were obvious, namely pepsin A-2/3 which maintains its activity in the weakly acidic pH region over pH 3 and pepsin A-1, which does not. Hydrolysis of oxidized insulin B chain by goat pepsins A occurred primarily at Ala14-Leu15 and Leu15-Tyr16 bonds.

Pepsinogen synthesis during long-term culture of porcine chief cells

The purpose of this study was to characterize time-dependent changes in pepsinogen (PG) synthesis of porcine gastric chief cells during long-term monolayer culture. Porcine chief cells were isolated by pronase/collagenase treatment of fundic mucosa and enriched by density gradient and counterflow centrifugation. PG isoenzymes were identified in [L-35S]methionine-labelled cultured chief cells by native polyacrylamide gel electrophoresis followed by phosphor imager analysis, protease detection and immunoblots with specific PG A and C antibodies. The obtained results suggest that porcine chief cell cultures, after an initial settling period, reached an approximate steady state in total protein content and synthesis as well as in PG content and isoenzyme pattern from days 3 to 9 of culture. The latter was characterized by the presence of at least two PG A and two PG C isoenzymes. During the supposed steady-state total PG synthesis averaged out at 34 +/- 2% of total protein synthesis, as detected by [L-35S]methionine incorporation, due to the synthesis of, mainly, PG A2 and, to a much lesser extent, PG C and A1. In line with an active secretion, PG A2 proportion was on average significantly higher in released (44 +/- 3%) than in intracellular labelled proteins (19 +/- 2%). In addition, PG release from chief cells cultured for 6 and 9 days could be stimulated by cholecystokinin-octapeptide. These data suggest that porcine chief cells in monolayer culture are a model well suited for the quantitative and qualitative characterization of PG isoenzyme synthesis and release during long-term investigations, for which an establishment of a culture steady state appears to be a useful prerequisite.

Asian macaque pepsinogens and pepsins

Five pepsinogens were purified from the gastric mucosa of eight species of Asian macaques. The chromatographic behavior of each pepsinogen was essentially the same but differed from human and other mammalian pepsinogens. The major pepsinogen in each species was pepsinogen A-1, accounting for 29-48% of the total. Amino acid compositions and some enzymatic properties of derived pepsins were similar for the various monkey species. This high degree of similarity confirms that these species are closely related to one another.

Gastric chief cell-specific transcription of the pepsinogen A gene

The molecular mechanisms underlying the regulation of pepsinogen A (PGA) gene expression in mammalian cells are poorly understood. In this paper we describe the structural and functional analysis of the pepsinogen A gene promoter in the pig. By genomic Southern analyses we demonstrate that, in contrast with human PGA genes which are amplified and organized in haplotypes, only a single PGA gene is present per haploid porcine genome. With the aim of identifying promoter elements mediating the gastric mucosa cell-specific transcription of the PGA gene in pig, we isolated a PGA gene from a porcine genomic library. The nucleotide sequence of the first exon and 1.7 kb of the upstream DNA region were determined and compared with the corresponding regions of the human PGA gene encoding isozymogen Pg5. In order to study the promoter activity of the PGA gene a functional assay was developed: we succeeded in obtaining primary monolayer cultures of porcine gastric mucosal chief cells, suitable for transfection. Fragments of 5'-flanking and noncoding first exon sequences of the porcine and human PGA genes were linked to the chloramphenicol acetyltransferase (CAT) gene. The transcriptional activity of these hybrid genes was assessed in transient expression assays upon transfection (lipofection) of gastric and nongastric cells. Whereas PGA 5'-flanking sequences showed no promoter activity in nongastric cell types, the DNA region from -205 to +21 was found to be sufficient to direct expression of the porcine PGA constructs in a cell-specific manner. Further deletion analysis of the proximal promoter fragment identified several regions (-205 to -167, -127 to -67 and +2 to +21) acting synergistically in the transcriptional regulation of the PGA gene. In contrast, all human PGA-CAT constructs used failed to show promoter activity in porcine gastric chief cells, indicating species-specific control of PGA gene expression. In addition, the transcriptional activity of the porcine PGA promoter in chief cells from pig was completely abolished by in vitro CpG methylation. Footprint analyses of the proximal promoter fragment using nuclear extracts from either porcine gastric mucosal chief cells or liver revealed some notable differences between both extracts, which might reflect the interaction with (a) cell-specific factor(s).

Pharmacological isolation and characterization of NMDA receptor-mediated synaptic potential in the dentate gyrus of rat hippocampal slices

We attempted to observe the dentate gyrus field potential evoked by low-frequency stimulation of the perforant path in Mg(2+)-free medium and identify the N-methyl-D-aspartate (NMDA) receptor-mediated synaptic potential using rat hippocampal slices. When perfusing solution was changed from normal medium (1.3 mM Mg2+) to Mg(2+)-free medium, the evoked potential was greatly increased and secondary population spikes appeared following a primary population spike. The evoked potential recorded in Mg(2+)-free medium was only partly blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA receptor antagonist. The CNQX-resistant component of the evoked potential in Mg(2+)-free medium was completely abolished by 30 microM DL-2-amino-5-phosphonovalerate, a NMDA receptor antagonist, indicating that the NMDA receptor-mediated synaptic response can be isolated by masking the non-NMDA receptor-mediated component of the evoked potential under the Mg(2+)-free condition. The isolated NMDA receptor-mediated synaptic potential was also blocked by 7-chlorokynurenate, an antagonist at the glycine site of the NMDA receptor, and restored by the concomitant presence of glycine. Observation of pharmacologically isolated NMDA receptor-mediated synaptic potential is a simple and good method for studying the direct effects of drugs on NMDA receptor-mediated responses.

Separation of porcine pepsinogen A and progastricsin. Sequencing of the first 73 amino acid residues in progastricsin

Porcine pepsinogen A (EC 3.4.23.1) and progastricsin (EC 3.4.23.3) have been separated by chromatography on DEAE-cellulose followed by chromatography on DEAE-Sepharose. Agar gel electrophoresis at pH 6.0 showed the presence of three components of pepsinogen A and two of progastricsin. During activation at pH 2 a segment of 43 amino acid residues (the prosegment peptide) is cleaved from the N-terminus of progastricsin. The sequence of this was determined; in addition, the first 30 residues of gastricsin were sequenced. The sequence of the first 73 amino acid residues of progastricsin shows an overall identity with progastricsins from man, monkey and rat of 67%. The overall identity with other zymogens for gastric proteinases is 27%. The highly conserved Lys36p (pig pepsinogen A numbering) is changed to Arg in porcine progastricsin.

Cystatin C based peptidyl diazomethanes as cysteine proteinase inhibitors: influence of the peptidyl chain length

The peptidyl diazomethanes Cbz-Gly-CHN2, Boc-Val-Gly-CHN2, H-Leu-Val-Gly-CHN2, Cbz-Leu-Val-Gly-CHN2 and Cbz-Arg-Leu-Val-Gly-CHN2, with peptidyl portions modelled after the proposed cysteine proteinase interacting N-terminal segment of human cystatin C, were synthesized. Their efficiency as cysteine proteinase inhibitors was tested against papain, human cathepsin B and bovine cathepsin B. All, except Cbz-Gly-CHN2, were found to be irreversible inhibitors of the tested enzymes. Each addition of an amino acid residue to their peptidyl portions resulted in an increased inhibition rate of all three enzymes. These data suggest that the arginyl residue of the tetrapeptidyl diazomethane, and also the corresponding arginyl residue in native cystatin C, interact with a S4 substrate pocket subsite of both papain and cathepsin B. The most efficient inhibitor, Cbz-Arg-Leu-Val-Gly-CHN2, inhibited papain and cathepsin B with rate constants of the same order of magnitude as those for L-3-carboxy-trans-2,3-epoxypropionyl-leucylamido-(4-guanidin o)butane (E-64). The high water-solubility of Cbz-Arg-Leu-Val-Gly-CHN2 allowing it to be dissolved to molar concentrations without use of non-physiological additives, makes it suitable for in vitro and in vivo cysteine proteinase inhibition studies.

Immunohistochemical and biochemical identification of pepsinogen isozymes in the hamster lungs: induction by polychlorinated biphenyls

Pepsinogens are acid protease enzymes of pepsin usually found in gastric mucosa. In the present study, we demonstrated the presence of pepsinogen isozymes in male Syrian golden hamster lung tissues by a combined immunohistochemical and biochemical approach. Immunohistochemically, using rat pepsinogen 1 antibody, pepsinogen positive cells were observed mainly in the epithelia of the terminal bronchioles. They demonstrated morphological features of Clara cells. The pepsinogen isozyme pattern of lung tissue determined by polyacrylamide gel electrophoresis was similar to that of stomach mucosa. Treatment of hamsters with polychlorinated biphenyls at a dose of 500 mg/kg body weight ip caused a 2.8-fold increase in pepsinogen content (p less than 0.01) as well as increase in numbers of pepsinogen positive cells in the lung.

Purification and characterization of inhibitor against the cysteine proteinase of Rana catesbeiana

1. Inhibitors of cysteine proteinase were found in tadpole tail of metamorphosing bullfrog. 2. One of the inhibitors was purified by affinity chromatography with CM-papain agarose, gel filtration with Superose 12 and ion exchange chromatography with Mono S. 3. The molecular weight of the inhibitor was 130,000-140,000 and the isoelectric point was pH 9.6. 4. The inhibitor had inhibitory effects on ficin, papain and tadpole tail cysteine proteinase. 5. The inhibitor is possibly involved in the regulation of muscle degradation in tail regression of metamorphosing tadpole.

Specificity of milk-clotting enzymes towards bovine kappa-casein

Limited proteolysis of bovine kappa-casein has been investigated with porcine pepsin A and C, and with the 2 microbial proteinases Mucor miehei proteinase and Endothia parasitica proteinase. The liberated C-terminal glycomacropeptide of kappa-casein was isolated after precipitation in 3% trichloroacetic acid followed by high-performance gel-permeation chromatography on a TSK G3000 SW column. From amino acid analyses and N-terminal sequencing of the liberated peptide it is concluded that porcine pepsin A, C and Mucor miehei proteinase cleave the same bond as chymosin: Phe-105-Met-106 whereas Endothia parasitica proteinase cleaves the bond Ser-104-Phe-105.

Nucleotide sequence and expression in Escherichia coli of cDNA of swine pepsinogen: involvement of the amino-terminal portion of the activation peptide segment in restoration of the functional protein

A clone, pSPcA2, which carries the full-length swine pepsinogen cDNA was isolated. The coding sequence comprised the signal peptide [15 amino acids (aa)], the activation peptide segment (44 aa) and mature pepsin (327 aa). The deduced amino acid sequence agrees with the published sequence with two exceptions. Asparagine instead of aspartate is present at aa positions 19 and 308. Two types of plasmids, pAS and pUCtacSPc series, were constructed for expressing swine pepsinogen cDNA. These plasmids directed the synthesis of polypeptides which were detected by employing an antibody to swine pepsinogen. However, all the polypeptides formed aggregates and showed no acid protease activity. Only the protein directed by pAS5 regained the acid protease activity after renaturation procedures. The activity was completely inhibited by pepstatin. Furthermore, the renatured pAS5 protein was spontaneously converted to pepsin under acidic conditions. The presence of Arg-8 in the activation peptide segment appears important for the stabilization of the pepsinogen molecule.

Characterization of a chymosin-like pepsin from the dogfish Scyliorhinus canicula

1. Pepsin II extracted from the gastric mucosa of Scyliorhinus canicula has been characterized and compared to calf chymosin. 2. The kcat and Km of the dogfish enzyme for the synthetic hexapeptide Leu-Ser-Phe(NO2)-Nle-Ala-Leu-OMe have been determined. The kcat/Km ratio is close to that of calf chymosin. Its milk-clotting efficiency is however 21-fold lower than that of calf chymosin. 3. The proteolytic activity against haemoglobin is optimal at pH 2.5. It clots the milk up to pH 6.8. 4. The dogfish pepsin II shows relatively better activity at low temperatures than calf chymosin.

Aminoguanidine prevents diabetes-induced arterial wall protein cross-linking

Age-associated increases in collagen cross-linking and accumulation of advanced glycosylation products are both accelerated by diabetes, suggesting that glucose-derived cross-link formation may contribute to the development of chronic diabetic complications as well as certain physical changes of aging. Aminoguanidine, a nucleophilic hydrazine compound, prevented both the formation of fluorescent advanced nonenzymatic glycosylation products and the formation of glucose-derived collagen cross-links in vitro. Aminoguanidine administration to rats was equally effective in preventing diabetes-induced formation of fluorescent advanced nonenzymatic glycosylation products and cross-linking of arterial wall connective tissue protein in vivo. The identification of aminoguanidine as an inhibitor of advanced nonenzymatic glycosylation product formation now makes possible precise experimental definition of the pathogenetic significance of this process and suggests a potential clinical role for aminoguanidine in the future treatment of chronic diabetic complications.

Identification of monkey lung procathepsin D-II as a pepsinogen-C-like acid protease zymogen

Procathepsin D-II (Mr = 37 500) was purified from Japanese monkey lung at pH 7.0, and was shown to be converted to the active form, cathepsin D-II (Mr = 33 000) via an intermediate (Mr = 35 500) upon treatment at pH 3.0 and 14 degrees C. Procathepsin D-II was shown to be the inactive precursor of cathepsin D-II based on the following results: the former was inactive toward heat-denaturated casein at pH 5.4 whereas the latter was active; the former was not inactivated by diazoacetyl-DL-norleucine methyl ester in the presence of Cu2+ ion at pH 6.0 whereas the latter was inactivated rapidly under the same conditions; and the former had no affinity to pepstatin-Sepharose between pH 5 and 7 whereas the latter was adsorbed to it. With a rabbit antiserum against procathepsin D-II, cathepsin D-II, pepsinogen C and pepsin C of Japanese monkey were each found to give a single precipitin line which fused completely with each other on agarose plate. On the other hand, cathepsin D-I purified from the monkey lung, and pepsinogens A (I, II, III-1, III-2 and III-3) obtained from the monkey gastric mucosa failed to precipitate with the antiserum. With the antiserum against the monkey pepsinogen C, the same results were obtained. Further, procathepsin D-II and pepsinogen C were shown to have the same amino-terminal amino acid sequence, Ala-Val-Val-Lys-Val-Pro-Leu-Lys-Lys-Phe-Lys-. All these results indicate a strong similarity of procathepsin D-II and cathepsin D-II to pepsinogen C and pepsin C, respectively.

Pepsinogen in gastric carcinoma cells

Immunoperoxidase staining of 125 gastric carcinomas showed pepsinogen in tumour cells of seven (5.6%) cases. Carcinomas from other sites were negative. The phenomenon is probably too uncommon to be useful in identifying secondary carcinomas as gastric in origin, but it is of some biological interest.