[5] Chymotrypsinogens—chymotrypsins

Identifying signatures of proteolytic stability and monomeric propensity in O-glycosylated insulin using molecular simulation

Insulin has been commonly adopted as a peptide drug to treat diabetes as it facilitates the uptake of glucose from the blood. The development of oral insulin remains elusive over decades owing to its susceptibility to the enzymes in the gastrointestinal tract and poor permeability through the intestinal epithelium upon dimerization. Recent experimental studies have revealed that certain O-linked glycosylation patterns could enhance insulin's proteolytic stability and reduce its dimerization propensity, but understanding such phenomena at the molecular level is still difficult. To address this challenge, we proposed and tested several structural determinants that could potentially influence insulin's proteolytic stability and dimerization propensity. We used these metrics to assess the properties of interest from [Formula: see text] aggregate molecular dynamics of each of 12 targeted insulin glyco-variants from multiple wild-type crystal structures. We found that glycan-involved hydrogen bonds and glycan-dimer occlusion were useful metrics predicting the proteolytic stability and dimerization propensity of insulin, respectively, as was in part the solvent-accessible surface area of proteolytic sites. However, other plausible metrics were not generally predictive. This work helps better explain how O-linked glycosylation influences the proteolytic stability and monomeric propensity of insulin, illuminating a path towards rational molecular design of insulin glycoforms.

Design and syntheses of 7-nitro-2-aryl-4H-benzo[d][1,3]oxazin-4-ones as potent anticancer and antioxidant agents

A group of new nitro substituted benzoxazinones (3a-k) were synthesized from easily available 4-nitroanthranilic acid. All the synthesized compounds were characterized by FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry and elemental analysis. Anti-proliferative and pro-apoptotic potential of all the synthesized compounds (3a-k) was evaluated by MTT and Hoechst 33258 staining assay respectively whereas their antioxidant properties were determined via DPPH free radical scavenging assay. The most active compounds (3a, 3c and 3k) showed significant cytotoxic potential against HeLa cells with an inhibition of cell viability that ranged between 28.54 and 44.67% (P < 0.001). Albeit statistically different, the anti-proliferative effect of 3c was in close match with that of the reference drug doxorubicin. Likewise, the test compounds showed profound pro-apoptotic potential with an apoptotic index that ranged between 52.86 and 75.61%. Besides, the docking studies revealed a higher efficiency for compounds (3a and 3h) owing to their better affinity and inhibition constant (K_i = 4.397 and 3.713 nmol) respectively. The antioxidant potential of synthesized benzoxazinones (3a-k) was in close agreement with the experimental anticancer results with a percent inhibition from 34.45 to 85.93% as compared to standard (90.56%).

Synthesis, in vitro urease inhibitory potential and molecular docking study of benzofuran-based-thiazoldinone analogues

In continuation of our work on enzyme inhibition, the benzofuran-based-thiazoldinone analogues (1-14) were synthesized, characterized by HREI-MS, 1H and 13CNMR and evaluated for urease inhibition. Compounds 1-14 exhibited a varying degree of urease inhibitory activity with IC50 values between 1.2 ± 0.01 to 23.50 ± 0.70 µM when compared with standard drug thiourea having IC50 value 21.40 ± 0.21 µM. Compound 1, 3, 5 and 8 showed significant inhibitory effects with IC50 values 1.2 ± 0.01, 2.20 ± 0.01, 1.40 ± 0.01 and 2.90 ± 0.01 µM respectively, better than the rest of the series. A structure activity relationship (SAR) of this series has been established based on electronic effects and position of different substituents present on phenyl ring. Molecular docking studies were performed to understand the binding interaction of the compounds.

In-silico Designing, ADMET Analysis, Synthesis and Biological Evaluation of Novel Derivatives of Diosmin Against Urease Protein and Helicobacter pylori Bacterium

BACKGROUND

Designing drug candidates against the urease enzyme, which has been found responsible for many pathological disorders in human beings as well as in animals, was done by insilico means.

METHODS

Studies were carried out on a designed library of diosmin derivatives with the help of Schrodinger's maestro package of molecular docking software against a crystallographic complex of plant enzyme Jack bean urease (PDB ID: 3LA4). Best twelve derivatives of diosmin were selected for synthesis by considering their interaction energy along with docking score and were further investigated for antioxidant, urease inhibitory and Anti-H. pylori activity by in- vitro method along with ADMET analysis.

RESULTS

In-vitro results of series concluded compounds D2a, D2d and D7 (IC50 12.6 ± 0.002, 14.14 ± 0.001 and 15.64 ± 0.012 µM respectively in urease inhibition and 5.195 ± 0.036, 5.39 ± 0.020 and 5.64± 0.005 µM in antioxidant behavior against DPPH) were found to be significantly potent with excellent docking score -11.721, -10.795, -10.188 and binding energy -62.674, -63.352, -56.267 kJ/ mol as compared to standard drugs thiourea and acetohydroxamic acid (-3.459, -3.049 and -21.156 kJ/mol and - 17.454 kJ/mol) whereas compounds D2b, D5b, D5d and D6 were found moderate in urease inhibitory activity.

CONCLUSION

Selected candidates from the outcome of in-vitro urease inhibitory were further examined for anti- H. pylori activity by a well diffusion method against H. pylori bacterium (DSM 4867). Compound D2a showed good anti-H. Pylori activity with a zone of inhibition 10.00 ± 0.00 mm and MIC value 500µg/mL as compared to standard drug acetohydroxamic acid having a zone of inhibition 9.00 ± 0.50mm and MIC 1000µg/mL. In- silico studies played an important role in designing the potent ligands against urease protein as well as in explaining the binding pattern of designed and synthesized ligand within the active pocket of jack bean urease protein. ADMET studies were also carried out to check the drug similarity of designed compounds by the means of quikprop module of molecular docking software. Hence, the present investigation studies will provide a new vision for the discovery of potent agents against H. pylori and urease associated diseases.

Combined co-solvent and pressure effect on kinetics of a peptide hydrolysis: an activity-based approach

The application of co-solvents and high pressure has been reported to be an efficient means to tune the kinetics of enzyme-catalyzed reactions. Co-solvents and pressure can lead to increased reaction rates without sacrificing enzyme stability, while temperature and pH operation windows are generally very narrow. Quantitative prediction of co-solvent and pressure effects on enzymatic reactions has not been successfully addressed in the literature. Herein, we are introducing a thermodynamic approach that is based on molecular interactions in the form of activity coefficients of substrate and of enzyme in the multi-component solution. This allowed us to quantitatively predict the combined effect of co-solvent and pressure on the kinetic constants, i.e. the Michaelis constant K_M and the catalytic constant k_cat, of an α-CT-catalyzed peptide hydrolysis reaction. The reaction was studied in the presence of different types of co-solvents and at pressures up to 2 kbar, and quantitative predictions could be obtained for K_M, k_cat, and finally even primary Michaelis-Menten plots using activity coefficients provided by the thermodynamic model PC-SAFT.

Evolution of digestive enzymes and dietary diversification in birds

As the most species-rich class of tetrapod vertebrates, Aves possesses diverse feeding habits, with multiple origins of insectivory, carnivory, frugivory, nectarivory, granivory and omnivory. Since digestive enzymes mediate and limit energy and nutrient uptake, we hypothesized that genes encoding digestive enzymes have undergone adaptive evolution in birds. To test this general hypothesis, we identified 16 digestive enzyme genes (including seven carbohydrase genes (hepatic amy, pancreatic amy, salivary amy, agl, g6pc, gaa and gck), three lipase genes (cyp7a1, lipf and pnlip), two protease genes (ctrc and pgc), two lysozyme genes (lyz and lyg) and two chitinase genes (chia and chit1)) from the available genomes of 48 bird species. Among these 16 genes, three (salivary amy, lipf and chit1) were not found in all 48 avian genomes, which was further supported by our synteny analysis. Of the remaining 13 genes, eight were single-copy and five (chia, gaa, lyz, lyg and pgc) were multi-copy. Moreover, the multi-copy genes gaa, lyg and pgc were predicted to exhibit functional divergence among copies. Positively selected sites were detected in all of the analyzed digestive enzyme genes, except agl, g6pc, gaa and gck, suggesting that different diets may have favored differences in catalytic capacities of these enzymes. Furthermore, the analysis also revealed that the pancreatic amylase gene and one of the lipase genes (cyp7a1) have higher ω (the ratio of nonsynonymous to the synonymous substitution rates) values in species consuming a larger amount of seeds and meat, respectively, indicating an intense selection. In addition, the gck carbohydrase gene in species consuming a smaller amount of seeds, fruits or nectar, and a lipase gene (pnlip) in species consuming less meat were found to be under relaxed selection. Thus, gene loss, gene duplication, functional divergence, positive selection and relaxed selection have collectively shaped the evolution of digestive enzymes in birds, and the evolutionary flexibility of these enzymes may have facilitated their dietary diversification.

Bioactive chemical constituents of Duboscia macrocarpa Bocq., and X-ray diffraction study of 11β, 12β-epoxyfriedours-14-en-3α-ol

A new γ-lactone triterpenoid, Evodoulolide (1) and a new triterpenoid Duboscic acid B (2), along with five known compounds, maslinic acid (3), arboreic acid (4), (E)-3-(4-hydroxyphenyl)-N-[2-(4-hydroxyphenyl) ethyl] prop-2-enamide (5), (E)-heptacos-19-enoic acid (6) and 11β,12β-epoxyfriedours-14-en-3α-ol (7) were isolated from the trunk wood of Duboscia macrocarpa. Their structures were elucidated from extensive ¹D- and ²D-NMR and MS and by comparison of their spectra with published data. Compounds 1, 3, 5 and 6 exhibited significant α-glucosidase inhibitory activity. Compound 5 was found to be a potent inhibitor (IC₅₀=5.1±0.1μM) of α-glucosidase as compared to acarbose (IC₅₀=625.0±1μM) used as standard drug. These compounds did not show anti-glycation activity using the BSA-MG glycation model or inhibition against the α-chymotrypsin enzyme. The chemotaxonomic connotation of the isolated secondary metabolites is also herein described. The single-crystal X-ray and absolute configuration diffraction analysis of 11α, 12α-epoxyfriedours-14-en-3-ol (7) is also described here for the first time.

Proteomic Analysis of Trichinella spiralis Adult Worm Excretory-Secretory Proteins Recognized by Sera of Patients with Early Trichinellosis

The most commonly used serodiagnostic antigens for trichinellosis are the excretory-secretory (ES) antigens from T. spiralis muscle larvae (ML), but the specific antibodies against the ML ES antigens are usually negative during early stage of Trichinella infection. The recent studies demonstrated that T. spiralis adult worm (AW) antigens were recognized by mouse or swine infection sera on Western blot as early as 7–15 days post-infection (dpi), the AW antigens might contain the early diagnostic markers for trichinellosis. The purpose of this study was to screen early diagnostic antigens in T. spiralis AW ES proteins recognized by sera of early patients with trichinellosis. T. spiralis AW were collected at 72 h post-infection (hpi), and their ES antigens were analyzed by SDS-PAGE and Western blot. Our results showed that 5 protein bands (55, 48–50, 45, 44, and 36 kDa) were recognized by sera of early patients with trichinellosis collected at 19 dpi, and were subjected to shotgun LC–MS/MS and bioinformatics analyses. A total of 185 proteins were identified from T. spiralis protein database, of which 116 (67.2%) proteins had molecular weights of 30∼60 kDa, and 125 (67.6%) proteins with pI 4–7. Bioinformatic analyses showed that the identified proteins have a wide diversity of biological functions (binding of nucleotides, proteins, ions, carbohydrates, and lipids; hydrolase, transferase, and oxidoreductase, etc.). Several enzymes (e.g., adult-specific DNase II, serine protease and serine protease inhibitor) could be the invasion-related proteins and early diagnostic markers for trichinellosis. Moreover, recombinant T. spiralis serine protease (rTsSP-ZH68) was expressed in E. coli and its antigenicity was analyzed by Western blot with the early infection sera. The rTsSP-ZH68 was recognized by sera of infected mice at 8–10 dpi and sera of early patients with trichinellosis at 19 dpi. T. spiralis AW proteins identified in this study, especially serine protease, are the promising early diagnostic antigens and vaccine candidates for trichinellosis.

α-Chymotrypsin regulates free fatty acids and UCHL-1 to ameliorate N-methyl nitrosourea induced mammary gland carcinoma in albino wistar rats

This study was undertaken to investigate the effect of α-chymotrypsin on methyl nitrosourea (MNU) induced mammary gland carcinoma in albino wistar rats. Animals were randomized into four groups (six animals in each). Group I (sham control 0.9 % normal saline p.o.); Group II (toxic control, MNU 47 mg/kg, i.v.); Group III (α-chymotrypsin, 5 mg/kg, p.o.); Group IV (α-chymotrypsin, 10 mg/kg p.o.). Toxicity was induced by single i.v. injection of MNU followed by α-chymotrypsin supplementation therapy for 100 days. MNU treatment was evident with increased alveolar bud count, differentiation score, upregulated inflammatory enzymes markers (COX, LOX and NO) antioxidative stress markers (TBARs, SOD, catalase and GSH).MNU associated toxicity was also ascertained by PGP 9.5 and NF-κB expression in the mammary gland tissue followed by FAME analysis for fatty acid profiling. α-chymotrypsin afforded significant protection against the deleterious effects of MNU.

EC-QCL mid-IR transmission spectroscopy for monitoring dynamic changes of protein secondary structure in aqueous solution on the example of β-aggregation in alcohol-denaturated α-chymotrypsin

In this work, a novel EC-QCL-based setup for mid-IR transmission measurements in the amide I region is introduced for monitoring dynamic changes in secondary structure of proteins. For this purpose, α-chymotrypsin (aCT) acts as a model protein, which gradually forms intermolecular β-sheet aggregates after adopting a non-native α-helical structure induced by exposure to 50 % TFE. In order to showcase the versatility of the presented setup, the effects of varying pH values and protein concentration on the rate of β-aggregation were studied. The influence of the pH value on the initial reaction rate was studied in the range of pH 5.8-8.2. Results indicate an increased aggregation rate at elevated pH values. Furthermore, the widely accessible concentration range of the laser-based IR transmission setup was utilized to investigate β-aggregation across a concentration range of 5-60 mg mL(-1). For concentrations lower than 20 mg mL(-1), the aggregation rate appears to be independent of concentration. At higher values, the reaction rate increases linearly with protein concentration. Extended MCR-ALS was employed to obtain pure spectral and concentration profiles of the temporal transition between α-helices and intermolecular β-sheets. Comparison of the global solutions obtained by the modelled data with results acquired by the laser-based IR transmission setup at different conditions shows excellent agreement. This demonstrates the potential and versatility of the EC-QCL-based IR transmission setup to monitor dynamic changes of protein secondary structure in aqueous solution at varying conditions and across a wide concentration range. Graphical abstract EC-QCL IR spectroscopy for monitoring protein conformation change.

Metal organic frameworks mimicking natural enzymes: a structural and functional analogy

In this review, we have portrayed the structure, synthesis and applications of a variety of biomimetic MOFs from an unprecedented angle.

Proteolytic Systems in Milk: Perspectives on the Evolutionary Function within the Mammary Gland and the Infant

Milk contains elements of numerous proteolytic systems (zymogens, active proteases, protease inhibitors and protease activators) produced in part from blood, in part by mammary epithelial cells and in part by immune cell secretion. Researchers have examined milk proteases for decades, as they can cause major defects in milk quality and cheese production. Most previous research has examined these proteases with the aim to eliminate or control their actions. However, our recent peptidomics research demonstrates that these milk proteases produce specific peptides in healthy milk and continue to function within the infant's gastrointestinal tract. These findings suggest that milk proteases have an evolutionary function in aiding the infant's digestion or releasing functional peptides. In other words, the mother provides the infant with not only dietary proteins but also the means to digest them. However, proteolysis in the milk is controlled by a balance of protease inhibitors and protease activators so that only a small portion of milk proteins are digested within the mammary gland. This regulation presents a question: If proteolysis is beneficial to the infant, what benefits are gained by preventing complete proteolysis through the presence of protease inhibitors? In addition to summarizing what is known about milk proteolytic systems, we explore possible evolutionary explanations for this proteolytic balance.

Over-transcription of genes in a parathion-resistant strain of mosquito Culex pipiens quinquefasciatus

Insecticide resistance is an evolutionary adaptation that develops quite quickly in mosquitoes because of the high selection pressure of chemical insecticides, rapid generation time and large population size. Identification of genes associated with insecticide resistance is fundamental to understand the complex processes responsible for resistance. We compared the gene transcriptional profiles of parathion-resistant and -susceptible Culex pipiens quinquefasciatus using a combination of suppression subtractive hybridization and complementary DNA (cDNA) microarray techniques. A total of 278 colonies were selected from the resistant-susceptible mosquito subtractive library, 38 of which showed more than two fold stronger immunoblotting signals in the resistant strain than in the susceptible strain using cDNA microarray selection. The sequencing results showed that the 38 colonies can be matched to 12 genes of C. p. quinquefasciatus. Eight genes were confirmed to be overexpressed by more than two fold in the resistant strain. These genes encode chymotrypsin-1, theta glutathione S-transferase, lipase 3, larval serum protein 1 β chain, cytochrome b, mitochondrial ribosomal large subunit, 28S rRNA, and a protein with unknown function. This study serves as a preliminary attempt to identify new genes associated with organophosphate resistance in this mosquito species and provides insights into the complicated physiological phenomenon of insecticide resistance.

Serum stability of selected decapeptide agonists of KISS1R using pseudopeptides

Metastin/kisspeptin, a 54-amino acid peptide, is the ligand of the G-protein-coupled receptor KISS1R which plays a key role in pathways that regulate reproduction and cell migration in many endocrine and gonadal tissues. The N-terminally truncated decapeptide, metastin(45-54), has 3-10 times higher receptor affinity and intracellular calcium ion-mobilizing activity but is rapidly inactivated in serum. In this study we designed and synthesized stable KISS1R agonistic decapeptide analogs with selected substitutions at positions 47, 50, and 51. Replacement of glycine with azaglycine (azaGly) in which the α-carbon is replaced with a nitrogen atom at position 51 improved the stability of amide bonds between Phe(50)-Gly(51) and Gly(51)-Leu(52) as determined by in vitro mouse serum stability studies. Substitution for tryptophan at position 47 with other amino acids such as serine, threonine, β-(3-pyridyl)alanine, and D-tryptophan (D-Trp), produced analogs that were highly stable in mouse serum. D-Trp(47) analog 13 showed not only high metabolic stability but also excellent KISS1R agonistic activity. Other labile peptides may have increased serum stability using amino acid substitution.

Characterization of high-molecular-weight nonnative aggregates and aggregation kinetics by size exclusion chromatography with inline multi-angle laser light scattering

Size exclusion chromatography with an inline multi-angle light scattering detector (SEC-MALS) was assessed as a means to characterize and monitor the formation of soluble, high-molecular-weight (HMW) protein aggregates so as to better quantify and model nonnative aggregation kinetics. Assay configuration and robustness were tested with respect to sample preparation, column type, and assay variability. Independent comparison of SEC-MALS with batch light scattering analysis indicates good agreement between the two methods. Weight-average molecular weight (M(w)), radius of gyration (R(g)), apparent polydispersity, and mass fraction monomer (m) together are shown to provide qualitative and quantitative experimental signatures to distinguish high-MW aggregate growth via chain polymerization versus that via aggregate-aggregate condensation. Mechanistic treatment of aggregation kinetics monitored by SEC-MALS is illustrated by data regression using a recently developed Lumry-Eyring Nucleated Polymerization model that explicitly accounts for aggregate nucleation and competing growth via chain- and condensation-polymerization. The combination of time-dependent M(w) and m data are shown to provide a convenient and robust means to separate and quantify characteristic time scales or rate coefficients for concurrent stages of irreversible aggregation. In addition, the scaling of R(g) with M(w) for HMW aggregates provides useful insights into aggregate morphology and mechanisms of aggregate growth.

Digestion of the lambda cI repressor with various serine proteases and correlation with its three dimensional structure

Partial proteolysis of the lambda cI repressor has been carried out systematically with trypsin, chymotrypsin, elastase, endoproteinase Glu-C, kallikrein, and thrombin. The cleavage sites have been determined by (i) comparison of fragments produced and observed in SDS-polyacrylamide gel with known fragments and plots of distance migrated versus log (molecular weight of fragment), (ii) partial Edman sequencing of the stable C-terminal fragments to identify cleavage points, and (iii) electrospray mass spectrometry of fragments produced. Most cleavage points are found to occur in the region 86-137, saving some in the N-terminal domain observed for trypsin and Glu-C. Region 86-137 can be further subdivided into three regions 86-91, 114-121, and 128-137 prone to cleavage, with intermediate regions resistant to cleavage to all six proteases. These resistant regions show that much of the region 93-131 previously called a 'linker' is actually part of the C-domain as first proposed in all models from our laboratory. Region 92-114 includes the cleavage site Ala-Gly, which must be buried in the intact repressor. The observed cleavage points in region 114-137 can be used to judge the best among three previously proposed models since they differ from each other in the structure of region 93-131. Model 1j5g is adjudged to be better than model 1lwq (which is based on 1kca, a crystal structure) as susceptible residues are more exposed in the former and lack of cleavages at six sites is better explained. Likewise, the models 1j5g and 1lwq are compared with a recent crystal structure of fragment 101-229 in 2ho0 and another low resolution crystal structure in 3bdn.

Diapause in the mosquito Culex pipiens evokes a metabolic switch from blood feeding to sugar gluttony

A key characteristic of overwintering dormancy (diapause) in the mosquito Culex pipiens is the switch in females from blood feeding to sugar gluttony. We present evidence demonstrating that genes encoding enzymes needed to digest a blood meal (trypsin and a chymotrypsin-like protease) are down-regulated in diapause-destined females, and that concurrently, a gene associated with the accumulation of lipid reserves (fatty acid synthase) is highly up-regulated. As the females then enter diapause, fatty acid synthase is only sporadically expressed, and expression of trypsin and chymotrypsin-like remains undetectable. Late in diapause (2-3 months at 18 degrees C), the genes encoding the digestive enzymes begin to be expressed as the female prepares to take a blood meal upon the termination of diapause. Our results thus underscore a molecular switch that either capacitates the mosquito for blood feeding (nondiapause) or channels the adult mosquito exclusively toward sugar feeding and lipid sequestration (diapause).

Evidence for 'lock and key' character in an anti-phosphonate hydrolytic antibody catalytic site augmented by non-reaction centre recognition: variation in substrate selectivity between an anti-phosphonate antibody, an anti-phosphate antibody and two hydrolytic enzymes

The substrate selectivities of an anti-phosphonate and an anti-phosphate kinetically homogeneous polyclonal catalytic antibody preparation and two hydrolytic enzymes were compared by using hapten-analogous and truncated carbonate and ester substrates each containing a 4-nitrophenolate leaving group. Syntheses of the truncated substrates devoid of recognition features in the non-leaving group parts of the substrates are reported. The relatively high kinetic selectivity of the more active anti-phosphonate antibody preparation is considered to depend on a relatively rigid catalytic site with substantial reaction centre specificity together with other important recognition interactions with the extended non-leaving group part of the substrate. In contrast, the less catalytically active, more flexible anti-phosphate antibody exhibits much lower kinetic selectivity for the substrate reaction centre comparable with that of the hydrolytic enzymes with activity much less dependent on recognition interactions with the non-leaving group part of the substrate. The ways in which haptenic flexibility and IgG architecture might contribute to the differential kinetic selectivities are indicated.

Activation of caspases and serine proteases during apoptosis induced by onconase (Ranpirnase)

Onconase (ONC) is a ribonuclease isolated from amphibian oocytes that is cytostatic and cytotoxic to numerous tumor lines. ONC shows in vivo anti-tumor activity in mouse tumor models and is currently in Phase III clinical trials. Previous studies indicated that ONC induces apoptosis of the target cells most likely along the mitochondrial pathway involving caspase-9 as the initiator caspase. We have recently developed an approach to detect the activation of serine (Ser) proteases during apoptosis. The method is based on affinity labeling of Ser protease active centers with fluorochrome-tagged inhibitors. The aim of the present study was to reveal whether Ser proteases are activated during apoptosis induced by ONC. Human leukemic HL-60 cells were treated with ONC for up to 72 h and then exposed to 5(6)-carboxyfluoresceinyl-L-phenylalanylchloromethyl ketone (FFCK) or 5(6)-carboxyfluoresceinyl-L-leucylchloromethyl ketone (FLCK), the fluorescing green reagents reactive with active centers of the chymotrypsin-like enzymes that cleave proteins at the Phe (FFCK) or Leu (FLCK) site. Activation of caspases was assayed in the same cells using sulforhodamine-labeled (fluorescing red) pan-caspases inhibitor (SR-VAD-FMK). Administration of 1.67 microM ONC into cultures of HL-60 cells led to the appearance of cells that bound SR-VAD-FMK as well as FFCK and FLCK. Most labeled cells had features characteristic of apoptosis. We interpret the binding of these ligands, which was irreversible and withstood cell fixation, as revealing activation of caspases and chymotrypsin-like Ser proteases. Because the induction of binding of each of the three ligands occurred at approximately the same time, the data suggest that during apoptosis caspases and Ser proteases may transactivate each other. The intercellular and subcellular pattern of binding SR-VAD-FMK vs FFCK or vs FLCK was different indicating a variability in abundance and localization of these enzymes within individual apoptotic cells. The FFCK- and FLCK-reactive proteins were of similar molecular mass, approximately 59 and approximately 57 kDa, respectively.

Purification and properties of an alkaline proteinase of Fusarium culmorum

The disease Fusarium head blight (scab) causes severe problems for farmers and for the industries that use cereals. It is likely that the fungi that cause scab (Fusarium spp.) use various enzymes when they invade grains. We are studying enzymes that the fungi may use to hydrolyze grain proteins. To do this, Fusarium culmorum was grown in a gluten-containing medium from which an alkaline serine proteinase with a molecular mass of 28.7 kDa was purified by size-exclusion and cation exchange chromatographies. The enzyme was maximally active at pH 8.3-9.6 and 50 degrees C, but was unstable under these conditions. It hydrolyzed the synthetic substrates N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide and, to a lesser extent, N-succinyl-Ala-Ala-Pro-Leu p-nitroanilide. It was inhibited by phenylmethanesulfonyl fluoride and chymostatin, but not by soybean trypsin or Bowman-Birk inhibitors. Parts of the amino-acid sequence were up to 82% homologous with those of several fungal subtilisins. One of the active site amino acids was detected and it occupied the same relative position as in the other subtilisins. Therefore, on the basis of these characteristics, the proteinase is subtilisin-like. Purification of the enzyme was complicated by the fact that, when purified, it apparently underwent autolysis. The presence of extraneous protein stabilized the activity.

Aberrant forms of alpha(2)-macroglobulin purified from patients with multiple sclerosis

The biochemical properties of alpha(2)-macroglobulin were investigated in four patients with multiple sclerosis and compared to alpha(2)-macroglobulin from healthy controls. An impaired stability of alpha(2)-macroglobulin from the multiple sclerosis patients was demonstrated as a spontaneous conversion to an electrophoretic"fast" form of alpha(2)-macroglobulin upon purification and storage, with a concomitant decrease in functional capacity to inhibit proteinases. The ability to form complexes with proteinases was significantly reduced in alpha(2)-macroglobulin purified from the multiple sclerosis patients. The aberrant molecular arrangements of the protein were not due to proteinase cleavages in the bait regions of alpha(2)-macroglobulin, as demonstrated by gel electrophoresis and protein sequencing. The number of functional thiol esters, however, was reduced in alpha(2)-macroglobulin purified from the multiple sclerosis patients, an observation compatible with the impaired proteinase binding property. Furthermore, differences in isoelectric points were observed between alpha(2)-macroglobulin from the multiple sclerosis patients and alpha(2)-macroglobulin from healthy controls. The results suggest that aberrant forms of alpha(2)-macroglobulin may be present in patients with multiple sclerosis.

Effect of solution pH on protein transport through ultrafiltration membranes

Although a number of previous studies have demonstrated that solution pH can have a dramatic effect on protein transport through ultrafiltration membranes, the exact origin of this behavior has been unclear. Experimental data were obtained for the transport of a broad range of proteins with different surface charge and molecular weight. The effective hydrodynamic size of the proteins was evaluated using size-exclusion chromatography. The membrane charge, both before and after exposure to a given protein, was evaluated using streaming potential measurements. In most cases, the electrostatic interactions were dominated by the distortion of the electrical double layer surrounding the protein, leading to a distinct maximum in protein transmission at the protein isoelectric point. Attractive electrostatic interactions did occur when the protein and membrane had a large opposite charge, causing a second maximum in transmission at a pH between the isoelectric points of the protein and membrane. The sieving data were in good agreement with theoretical calculations based on available models for the partitioning of charged solutes in cylindrical pores. Copyright 1999 John Wiley & Sons, Inc.

Purification and partial characterization of camel anionic chymotrypsin

An anionic chymotrypsin-like enzyme was isolated from a crude extract of camel pancreas by a three-step procedure consisting of anion-exchange chromatography, gel filtration, and hydrophobic interaction chromatography. The purified enzyme was homogeneous on native and SDS gel electrophoresis and on gel isoelectric focusing. Its molecular mass was estimated as 28.5 kDa and its isoelectric point was found to be 4.4. The enzyme differed markedly from bovine chymotrypsin A in its substrate specificity, showing considerably lower values of the specificity constant for its action on tyrosine, tryptophan, and phenylalanine esters. Its pH optimum was found to be 7.8. It showed lower kininase activity and was more susceptible to inhibition by a number of inhibitors than the bovine cationic chymotrypsin. On the other hand, the camel enzyme showed a much greater hydrolytic activity than the bovine enzyme toward a leucine ester. In terms of its size, charge, and substrate specificity the camel enzyme was very similar to anionic chymotrypsins that have been isolated from other species and thus appears to be a camel anionic chymotrypsin.

Biochemical and pharmacological characterization of FK706, a novel elastase inhibitor

FK706, sodium 2-[4-[[(S)-1-[[(S)-2-[[(RS)-3, 3, 3-trifluoro-1-isopropyl-2-oxopropyl]aminocarbonyl]pyrrolidin -1-yl]carbonyl]-2-methylpropyl] aminocarbonyl] benzoylamino] acetate, C26H32F3N4NaO7, is a synthetic water-soluble inhibitor of human neutrophil elastase. This compound demonstrated a competitive and slow-binding inhibition of human neutrophil elastase with a Ki of 4.2 nM. In studies using synthetic substrates, FK706 inhibited human neutrophil elastase activity and porcine pancreatic elastase activity with respective IC50 values of 83 and 100 nM. FK706, however, inhibited more weakly, (IC50 values > 340 microM) other serine proteinases such as human pancreatic alpha-chymotrypsin, human pancreatic trypsin and human leukocyte cathepsin G. FK706 also effectively inhibited the hydrolysis of bovine neck ligament elastin (2 mg/ml final concentration) by human neutrophil elastase (4 microg/ml final concentration) with an IC50 value of 230 nM. FK706 protected animals against human neutrophil elastase (50 microg/animal)-induced lung hemorrhage with ED50 values of 2.4 microg/animal by intratracheal administration and 36.5 mg/kg by intravenous administration, respectively. Subcutaneous administration of FK706 significantly suppressed human neutrophil elastase (20 microg/paw)-induced paw edema in mice in a dose-dependent manner (47% inhibition at a dose of 100 mg/kg). These results suggest that FK706 would be a useful tool for investigating the role of human neutrophil elastase in inflammatory disorders associated with an excess of elastase, such as pulmonary emphysema, adult respiratory distress syndrome, septic shock, cystic fibrosis, chronic bronchitis and rheumatoid arthritis.

Sulfated lipids as inhibitors of pancreatic trypsin and chymotrypsin in epithelium of the mammalian digestive tract

Cholesterol sulfate and I3SO3-GalCer, which were commonly contained in the epithelia of mammalian digestive tracts, were found to inhibit the activities of typical digestive enzymes, pancreatic trypsin and chymotrypsin, but steroid sulfates, gangliosides and the other membrane constituents did not show any inhibitory activity. The preincubation of trypsin with I3SO3-GalCer at 37 degrees C for 10min was necessary to inhibit the activity of trypsin, but cholesterol sulfate showed its inhibitory activity without preincubation. Sulfated lipid-treated enzyme gave the same Km as and lower Vmax than those of the original enzymes. Also, both sulfated lipids inhibited pronase from Streptomyces griseus, but not lysyl endopeptidase from Achromobacter lyticus. These findings indicate that cholesterol sulfate and I3SO3-GalCer in the digestive tract function as epithelial inhibitors to prevent tissue injury by endogenous and exogenous proteases.