Inhibition of cysteine protease papain by metal ions and polysulfide complexes,especially mercuric ion

Aim Cysteine proteases are closely associated with many human and non-human pathological processes and are potential targets for metal ions especially Hg^2＋ and the related species. In the present work, on the basis of to the general study on the effects of some metal ions on the activity of papain, a well-known representative of cysteine protease family, the inhibitory effects of Hg^2＋ and polysulfide complexes were studied. Results All the metal ions tested （Hg^2＋, Cu^2＋, Ag^＋, Au^3＋, Zn^2＋, Cd^2＋, Fe^3＋, Mn^2＋, Pb^2＋, Yb^3＋） inhibit the activity of papain anda good correlation between the inhibitory potency and softness-and-hardness was observed. Among the metals, Hg^2＋ was shown to be a potent inhibitor of papain with a Kiof 2 × 10^-7 mol·L^-1 among. Excessive amounts of glutathione and cysteine could reactivate the enzyme activity of papain deactivated by Hg^2＋. These evidences supported that Hg^2＋ might bind to the catalytic site of papain. Interestingly, Hg （Ⅱ） polysulfide complexes were for the first time found to inhibit papain with a Ki of 7 × 10^-6 mol·L^-1, whose potency is close to a well known mercury compound, thimerosal （Ki=2.7 × 10^-6）. In addition, Hg （Ⅱ） polysulfide complexes exhibit good permeability （ 1.9 × 10-5 cm· s^-1） to caco-2 monolayer. Conclusion These results suggested that mercury polysulfide complexes might be potential bioactive species in the interaction with cysteine proteases and other- SH-content proteins, providing a new clue to understand the mechanism of the toxicological and pharmacological actions of cinnabar and other insoluble mercury compounds.

Synthesis of N1-Substituted-3-aryl-4-alkyl-4, 5-dihydro-1H-1-pyra-zolethiocarboxamide as Novel Small Molecule Inhibitors of Cysteine Protease of T.cruzi

A series of N1-substituted-3-aryl-4-alkyl-4, 5-dihydro-1H-1-pyrazolethiocarboxamide were prepared from the Mannich bases of aryl ketones in good yields. Some derivatives were found to be active against the cysteine protease of T.cruzi..

Cysteine proteases as therapeutic targets:does selectivity matter? A systematic review of calpain and cathepsin inhibitors

Cysteine proteases continue to provide validated targets for treatment of human diseases.In neurodegenerative disorders,multiple cysteine proteases provide targets for enzyme inhibitors,notably caspases,calpains,and cathepsins.The reactive,active-site cysteine provides specificity for many inhibitor designs over other families of proteases,such as aspartate and serine;however,a)inhibitor strategies often use covalent enzyme modification,and b)obtaining selectivity within families of cysteine proteases and their isozymes is problematic.This review provides a general update on strategies for cysteine protease inhibitor design and a focus on cathepsin B and calpain 1 as drug targets for neurodegenerative disorders;the latter focus providing an interesting query for the contemporary assumptions that irreversible,covalent protein modification and low selectivity are anathema to therapeutic safety and efficacy.

Computational Analysis of Cysteine Proteases(Clan CA,Family C1) of Leishmania major to Find Potential Epitopic Regions

Leishmania is associated with a broad spectrum of diseases, ranging from simple cutaneous to invasive visceral leishmaniasis. Here, the sequences of ten cysteine proteases of types A, B and C of Leishmania major were obtained from GeneDB database. Prediction of MHC class I epitopes of these cysteine proteases was performed by NetCTL program version 1.2. In addition, by using BcePred server, different structural properties of the proteins were predicted to find out their potential B cell epitopes. According to this computational analysis, nine regions were predicted as B cell epitopes. The results provide useful information for designing peptide-based vaccines.

Identification of Molecular Marker Linked to Salt Tolerance Gene in Alfalfa

The study has established the F2 offspring obtained by crossing salt-tolerant with salt-sensitive alfalfa, and appraised the salt-tolerant F2 offspring seedling was evaluated in pot culture. With the F2 segregated population, the research has obtained a molecular marker linked with salt-tolerant genes of alfalfa using the improved BSA combined with RAPD. The RAPD PCR products were excised from the agarose gel and purified using a kit, then were mixed with pMD-18T vector and sequenced. Sequencing result indicated the RAPD marker was 1 438 bp in length. Similarity researches using blast in Genbank indicated that the nucleotide sequence of the RAPD marker showed 93% and 91% similarity with mth2-6el8 gene fragment （347 bp） and ruth2-33122 gene fragment （334 bp） of Medicago truncatula respectively. Medicago truncatula is a close relative of alfalfa and Mth2-6el8 is a molecular marker of the gene coding for a cysteine protease which was saltinducible in some plants. These results indicated the RAPD marker was possibly related to cysteine protease genes in alfalfa.

Rational drug design,synthesis,and biological evaluation of novel N-(2-arylaminophenyl)-2,3-diphenylquinoxaline-6-sulfonamides as potential antimalarial,antifungal,and antibacterial agents

Objective Sulfanilamide,sulfadiazine,and dapsone were the first sulfonamides to be used to treat malaria by disrupting the folate biosynthesis process,which is essential for parasite survival.Therefore,we aimed to synthesize novel N-(2-arylaminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide derivatives through a rational drug design approach.Methods All compounds were synthesized by the conventional method,and the products were characterized by spectral analysis(1 H NMR and mass spectrometry).The progression of the reaction was monitored using thin-layer chromatography(TLC).All the derivatives were analyzed for their effective binding mode in the allosteric site of the plasmodium cysteine protease falcipain-2.Antibacterial and antifungal activities were determined using the broth dilution method.Results S6(N-(2-thiazol-4 yl)-acetyl-aminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide and S9(N-(1 H-benzo[d]imidazol-2-yl)aminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide formed five hydrogen bonds;S8(N-(2-1 H-imidazol-2 yl)aminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide and S10(N-(1 H-benzo[d]imidazol-5-yl)aminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide formed four hydrogen bonds with the allosteric site of the enzyme.Considering the docking scores and formation of hydrogen bonds with the target enzyme,the novel derivatives were processed for wet lab synthesis.All the newly synthesized derivatives were subjected to in vitro antimalarial,antifungal,and antibacterial activities.All the derivatives exhibited sufficient sensitivity to the Plasmodium falciparum strain compared to the standards.Moreover,compounds S9 and S10 showed the most potent dual antimicrobial and antimalarial activities.They also exhibited powerful molecular interactions in molecular docking studies.Conclusion Based on the above results,it was concluded that N-(2-arylaminophenyl)-2,3-diphenylquinoxaline-6-sulfonamide derivatives have excellent biological potential to act as antimalarial,antifungal,and antibacterial agents.

Ultrastructural and enzymatic alterations in the ovary of Rhodnius prolixus infected with Trypanosoma rangeli

Objective:To investigate the morphological structure of ovarian follicular cells and biochemical parameters of both ovaries and fat bodies(sites of vitellogenesis)from Rhodnius(R.)prolixus infected with Trypanosoma(T.)rangeli.Methods:Adult virgin females of R.prolixus were fed upon a membrane apparatus containing heat-inactivated citrated rabbit blood and a suspension of T.rangeli epimastigotes(Macias strain).Females from the control group and all the males received parasite-free blood.Transmission electron microscopy was used to reveal the morphological aspects of ovarian follicle cells in both control and parasite-infected groups.Protein profile,proteolytic activities and Western blotting analyses were performed in either ovary or fat body samples of control and parasite-infected groups.Results:According to the ultrastructural data,T.rangeli infection elicited a degeneration process in the ovarian follicular cells of R.prolixus.Proteolytic assays indicated a reduction in the activity of aspartic peptidases in the ovary and fat body from parasite-infected group,while a significant increase in the cysteine peptidase activity was measured in both insect organs.Additionally,immunoblotting revealed that vitellogenin was overexpressed in the ovary of parasite-infected insects.Conclusions:T.rangeli infection seems to elicit an early programmed cell death in the ovarian follicle cells as well as induces the modulation on the activities of different peptidase classes in either ovaries or fat bodies and the overexpression of the vitellogenin in the ovary of R.prolixus.

Design, Synthesis and Antifungal Activity of 6-Fluoro-3,3a,4,5-tetrahydro-2H-pyrazolo[4,3-c]-quinoline-2-carboxamide Derivatives

A series of 6-fluoro-3,3a,4,5-tetrahydro-2H-pyrazolo[4,3-c]quinoline-2-carboxamide derivatives was designed based on the bioisosterism and combination principle in drug design. The target compounds were synthesized from substituted aniline through Michael addition, cyclization, Mannich reaction and condensation with 4-substituted semicarbazides, and the structures were confirmed by mass spectrometry（MS） and 1H NMR. The antifungal assay was carried out in vitro by two-fold dilution. The result shows that all the compounds are of antifungal activities against the tested fungi at different levels.

Molecular mechanisms of insect adaptation to plant defense： Lessons learned from a Bruchid beetle

Plants can accumulate, constitutively and/or after induction, a wide variety of defense compounds in their tissues that confer resistance to herbivorous insects. The naturally occurring plant resistance gene pool can serve as an arsenal in pest management via transgenic approaches. As insect-plant interaction research rapidly advances, it has gradually become clear that the effects of plant defense compounds are determined not only by their toxicity toward target sites, but also by how insects respond to the challenge. Insect digestive tracts are not passive targets of plant defense, but often can adapt to dietary challenge and successfully deal with various plant toxins and anti-metabolites. This adaptive response has posed an obstacle to biotechnology-based pest control approaches, which underscores the importance of understanding insect adaptive mechanisms. Molecular studies on the impact of protease inhibitors on insect digestion have contributed significantly to our understanding of insect adaptation to plant defense. This review will focus on exposing how the insect responds to protease inhibitors by both qualitative and quantitative remodeling of their digestive proteases using the cowpea bruchid-soybean cysteine protease inhibitor N system.

Inhibition and attenuation of pathogenicity of Porphyromonas gingivalis by leupeptin： A review

BACKGROUND： Porphyromonas gingivalis is a periodontal pathogen, which is considered to be a keystone pathogen for periodontitis. A diverse conglomerate of P. gingivalis virulence factors including lipopolysaccharide, fimbriae, capsular polysaccharide, haemagglutinin and cysteine proteases （Arg-gingipains and Lys-gingipain） are considered to be involved in the pathogenesis ofperiodontitis. Leupeptin is a cysteine protease inhibitor which is specific for Arg gingipains. The present review focuses on action of leupeptin on Arg gingipains. METHOD： A search was carried out systematically from the start till September, 2016. The search was made in Medline database via PubMed. The keywords enlisted were ＂leupeptin＂; ＂gingipains＂; ＂periodontitis＂ using Boolean operator ＂and.＂ RESULTS： The result was selection of 58 articles which linked leupeptin to periodontitis and gingipains; pathogenesis of periodontitis, pathogenicity of gingipains and role of leupeptin. CONCLUSION： It was concluded that leupeptin inhibits and attenuates a number of destructive activities of Arg gingipains including inhibition ofplatelet aggregation; inhibit degradation of LL-37, which is an antimicrobial peptide; blocking inhibition ofmonocyte chemoattractant protein; restoring level ofinterleukin-2; inhibiting degradation of collagen type I and IV to name a few.