Structural and mechanistic insights into a novel non-competitive Kunitz trypsin inhibitor from Adenanthera pavonina L. seeds with double activity toward serine- and cysteine-proteinases

Antifungal, Antimycobacterial, Protease and α‒Amylase Inhibitory Activities of a Novel Serine Bifunctional Protease Inhibitor from Adenanthera pavonina L. Seeds

Antifungal resistance poses a significant challenge to disease management, necessitating the development of novel drugs. Antimicrobial peptides offer potential solutions. This study focused on extraction and characterization of peptides from Adenanthera pavonina seeds with activity against Candida species, Mycobacterium tuberculosis, proteases, and α-amylases. Peptides were extracted in phosphate buffer and heated at 90°C for 10 min to create a peptide rich heated fraction (PRHF). After confirming antimicrobial activity and the presence of peptides, the PRHF underwent ion exchange chromatography, yielding retained and non-retained fractions. These fractions were evaluated for antimicrobial activity and cytotoxicity against murine macrophages. The least toxic and most active fraction underwent reversed-phase chromatography, resulting in ten fractions. These fractions were tested for peptides and antimicrobial activity. The most active fraction was rechromatographed on a reversed-phase column, resulting in two fractions that were assessed for antimicrobial activity. The most active fraction revealed a single band of approximately 6 kDa and was tested for inhibitory effects on proteases and α-amylases. Thermal stability experiments were conducted on the 6 kDa peptide at different temperatures followed by reassessment of antifungal activity and circular dichroism. The 6 kDa peptide inhibited yeasts, M. tuberculosis, human salivary and Tenebrio molitor larvae intestine α-amylases, and proteolytic activity from fungal extracts, and thus named ApPI. Remarkably, ApPI retained antifungal activity and conformation after heating and is primarily composed of α-helices. ApPI is a thermally stable serine protease/α-amylase inhibitor from A. pavonina seeds, offering promise as a foundational molecule for innovative therapeutic agents against fungal infections and tuberculosis.

Some morpholine tethered novel aurones: Design, synthesis, biological, kinetic and molecular docking studies

Enzymes are the biological macromolecules that have emerged as an important drug target as their upregulation/imbalance leads to various pathological conditions, such as inflammation, parasitic infection, Alzheimer's, cancer, and many others. Here, we designed and synthesized some morpholine tethered novel aurones and evaluated them as potential inhibitors for CTSB, α-amylase, lipase and activator for trypsin. All the newly synthesized compounds were fully characterized by various spectroscopic techniques (1H NMR, 13C NMR, HRMS) and the Z-configuration to them was assigned based on single crystal XRD data and 1H NMR chemical shift values. Further, the hybrids were evaluated for their intracellular (cathepsin B) and extracellular (trypsin, lipase, amylase) enzyme inhibition potencies. The in-vitro inhibition screening against cathepsin B revealed that most of the synthesized compounds are good competitive inhibitors (% inhibition = 22.91-75.04), with 6q (% inhibition = 75.04) and 6r (% inhibition = 71.13) as the eminent inhibitors of the series. At the same time, they exhibited weak to moderate inhibition towards amylase (% inhibition = 7.22-22.48) and lipase (% inhibition = 16.29-54.83). A significant trypsin activation (% activation = 107.42-196.47) was observed even at the micromolar concentration of the compounds. Furthermore, the drug-modeling studies showed a good correlation between the in-vitro experimental results and the calculated binding affinity of the screened compounds with all the tested enzymes. These findings are expected to provide a new lead in drug development for different pathological disorders wherever these enzymes are involved.

Evaluating the pesticidal impact of plant protease inhibitors: lethal weaponry in the co-evolutionary battle

In the arsenal of plant defense, protease inhibitors (PIs) are well-designed defensive products to counter field pests. PIs are produced in plant tissues by means of 'stable defense metabolite' and triggered on demand as the perception of the signal and well established as a part of plant active defense. PIs have been utilized for approximately four decades, initially as a gene-alone approach that was later replaced by multiple gene pyramiding/gene stacking due to insect adaptability towards the PI alone. By considering the adaptive responses of the pest to the single insecticidal gene, the concept of gene pyramiding gained continuous appreciation for the development of transgenic crops to deal with co-evolving pests. Gene pyramiding approaches are executed to bypass the insect's adaptive responses against PIs. Stacking PIs with additional insecticidal proteins, plastid engineering, recombinant proteinase inhibitors, RNAi-based methods and CRISPR/Cas9-mediated genome editing are the advanced tools and methods for next-generation pest management. Undoubtedly, the domain associated with the mechanism of PIs in the course of plant-pest interactions will occupy a central role for the advancement of more efficient and sustainable pest control strategies. © 2021 Society of Chemical Industry.

Intestinal Exposure to Food-Derived Protease Inhibitors: Digestion Physiology- and Gut Health-Related Effects

Plant-derived protease inhibitors (PI), such as Bowman-Birk inhibitors and Kunitz-type inhibitors, have been suggested to negatively affect dietary protein digestion by blocking the activity of trypsin and chymotrypsin in the human gastrointestinal system. In addition, some PIs may possess proinflammatory activities. However, there is also scientific evidence on some beneficial effects of PIs, for example, gut-related anti-inflammatory and chemopreventive activities in vitro and in vivo. Some PIs are sensitive to processing and digestion; thus, their survival is an important aspect when considering their positive and negative bioactivities. The aim of this review was to evaluate the relevance of PIs in protein digestion in humans and to discuss the potential of PIs from whole foods and as purified compounds in decreasing symptoms of bowel-related conditions. Based on the reviewed literature, we concluded that while the complex interactions affecting plant protein digestibility and bioavailability remain unclear, PI supplements could be considered for targeted purposes to mitigate inflammation and gastric pain.

A novel cysteine proteinase inhibitor from seeds of Enterolobium contortisiliquum and its effect on Callosobruchus maculatus larvae

This study focused on the characterization of a novel cysteine proteinase inhibitor from Enterolobium contortisiliquum seeds targeting the inhibition of the growth of Callosobruchus maculatus larvae, an important cosmopolitan pest of the cowpea Vigna unguiculata during storage. The inhibitor was isolated by ion-exchange besides of size exclusion chromatography. EcCI molecular mass is 19,757 Da, composed of two polypeptide chains. It strongly inhibits papain (Kiapp 0.036 nM) and proteinases from the midguts of C. maculatus (80 μg mL-1, 60% inhibition). The inhibitory activity is reduced by 40% after a heat treatment at 100 °C for 2 h. The protein displayed noxious activity at 0.5% and 1% (w/w) when incorporated in artificial seeds, reducing larval mass in 87% and 92%, respectively. Treatment of C. maculatus larvae with conjugated EcCI-FIT and subsequent biodistribution resulted in high fluorescence intensity in midguts and markedly low intensity in malpighian tubules and fat body. Small amounts of labeled proteins were detected in larvae feces. The detection of high fluorescence in larvae midguts and low fluorescence in their feces indicate the retention of the FITC conjugated EcCI inhibitor in larvae midguts. These results demonstrate the potential of the natural protein from E. contortisiliquum to inhibit the development of C. maculatus.

Adepamycin: design, synthesis and biological properties of a new peptide with antimicrobial properties

Antimicrobial peptides (AMP) are molecules with a broad spectrum of activities that have been identified in most living organisms. In addition, synthetic AMPs designed from natural polypeptides have been largely investigated. Here, we designed a novel AMP using the amino acid sequence of a plant trypsin inhibitor from Adenanthera pavonina seeds (ApTI) as a template. The 176 amino acid residues ApTI sequence was cleaved in silico using the Collection of Antimicrobial Peptides (CAMP_R3), through the sliding-window method. Further improvements in AMP structure were carried out, resulting in adepamycin, an AMP designed from ApTI. Adepamycin showed antimicrobial activity from 0.9 to 3.6 μM against Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus strains. Moreover, this peptide also displayed activity against Candida albicans and Candida tropicalis. No toxic effects were observed on healthy human cells. Studies on the mechanism of action of adepamycin were carried out using an E. coli and C. tropicalis. Adepamycin triggers membrane disturbances, leading to intracellular nucleic acids release in E. coli. For C. tropicalis, an initial interference with the plasma membrane integrity is followed by the formation of intracellular reactive oxygen species (ROS), leading to apoptosis. Structurally, adepamycin was submitted to circular dichroism spectroscopy, molecular modeling and molecular dynamics simulations, revealing an environment-dependent α-helical structure in the presence of 2,2,2- trifluoroethanol (TFE) and in contact with mimetic vesicles/membranes. Therefore, adepamycin represents a novel lytic AMP with dual antibacterial and antifungal properties.

Noncompetitive tight-binding inhibition of Anticarsia gemmatalis trypsins by Adenanthera pavonina protease inhibitor affects larvae survival

The economic loss in soybean crops caused by the Lepidoptera insects has encouraged the search for new strategies to control this pest, which are currently based on synthetic insecticides. This paper evaluated the ability of ApTI (Adenanthera pavonina trypsin inhibitor) to inhibit trypsin-like proteins from Anticarsia gemmatalis by docking, molecular dynamics, and enzymatic and survival assay. The docking and molecular dynamic simulation between trypsin and ApTI were performed using the program CLUSPRO and NAMD, respectively. The inhibitory constant K_i and the inhibition type were determined through chromogenic assays. The survival assay of neonatal larvae under treatment with artificial diet supplemented with ApTI was also performed. The ApTI binding site was predicted to block substrate access to trypsin due to four interactions with the enzyme, producing a complex with a surface area of 1,183.7 Ų . The kinetic analysis revealed a noncompetitive tight-binding mechanism. The survival curves obtained using Kaplan-Meier estimators indicated that the highest larvae mortality was 60%, using 1.2 mg of ApTI per 100 ml of artificial diet. The in vitro, in vivo, and in silico studies demonstrated that ApTI is a strong noncompetitive inhibitor of trypsin with biotechnological potential for the control of A. gemmatalis insect.

Comparison of physicochemical properties of recombinant buckwheat trypsin inhibitor (rBTI) and soybean trypsin inhibitor (SBTI)

The inhibitory activities of buckwheat trypsin inhibitor (rBTI) towards trypsin were compared with soybean trypsin inhibitor (SBTI) in terms of their sensitivities to temperature, pH, salt ions and organic solvents. Both rBTI and SBTI were stable over a broad pH range of 2.0-12.0. rBTI exhibited higher thermal stability than SBTI. The inhibitory activity of rBTI was decreased by Zinc ions (Zn2+), KSCN, vitamin C and urea, while that of SBTI remained unchanged. However, H2O2, Mg2+ and Cu2+ ions had no significant effects on the inhibitory activities of rBTI and SBTI. Acetonitrile enhanced the inhibitory activity of rBTI, but had no effect on SBTI, while dimethylacetamide (DMAC) increased the inhibitory effect of both rBTI and SBTI. On the contrary, the inhibitory activities of rBTI and SBTI were reduced by isopropyl alcohol and methanol. The inhibition constants Ki of rBTI and SBTI were calculated to be 7.41 × 10-9 M and 6.52 × 10-9 M, respectively.

Legumes Protease Inhibitors as Biopesticides and Their Defense Mechanisms against Biotic Factors

Legumes are affected by biotic factors such as insects, molds, bacteria, and viruses. These plants can produce many different molecules in response to the attack of phytopathogens. Protease inhibitors (PIs) are proteins produced by legumes that inhibit the protease activity of phytopathogens. PIs are known to reduce nutrient availability, which diminishes pathogen growth and can lead to the death of the pathogen. PIs are classified according to the specificity of the mechanistic activity of the proteolytic enzymes, with serine and cysteine protease inhibitors being studied the most. Previous investigations have reported the efficacy of these highly stable proteins against diverse biotic factors and the concomitant protective effects in crops, representing a possible replacement of toxic agrochemicals that harm the environment.

Effects of a Reserve Protein on Spodoptera frugiperda Development: A Biochemical and Molecular Approach to the Entomotoxic Mechanism

Talisin is a storage protein from Talisia esculenta seeds that presents lectin-like and peptidase inhibitor properties. These characteristics suggest that talisin plays a role in the plant defense process, making it a multifunctional protein. This work aimed to investigate the effects of chronic intake of talisin on fifth instar larvae of Spodoptera frugiperda, considered the main insect pest of maize and the cause of substantial economic losses in several other crops. The chronic intake of talisin presented antinutritional effects on the larvae, reducing their weight and prolonging the total development time of the insects. In addition, talisin-fed larvae also showed a significant reduction in the activity of trypsin-like enzymes. Midgut histology analysis of talisin-fed larvae showed alterations in the intestinal epithelium and rupture of the peritrophic membrane, possibly causing an increase of aminopeptidase activity in the midgut lumen. Talisin also proved to be resistant to degradation by the digestive enzymes of S. frugiperda. The transcription profile of trypsin, chymotrypsin and aminopeptidase genes was also analyzed through qPCR technique. Talisin intake resulted in differential expression of at least two genes from each of these classes of enzymes. Molecular docking studies indicated a higher affinity of talisin for the less expressed enzymes.

Dual Insecticidal Effects of Adenanthera pavonina Kunitz-Type Inhibitor on Plodia interpunctella is Mediated by Digestive Enzymes Inhibition and Chitin-Binding Properties

The Indianmeal moth, Plodia interpunctella, is one of the most damaging pests of stored products. We investigated the insecticidal properties of ApKTI, a Kunitz trypsin inhibitor from Adenanthera pavonina seeds, against P. interpunctella larvae through bioassays with artificial diet. ApKTI-fed larvae showed reduction of up to 88% on larval weight and 75% in survival. Trypsin enzymes extracted from P. interpunctella larvae were inhibited by ApKTI, which also demonstrated capacity to bind to chitin. Kinetic studies revealed a non-competitive inhibition mechanism of ApKTI for trypsin, which were further corroborated by molecular docking studies. Furthermore, we have demonstrated that ApKTI exhibits a hydrophobic pocket near the reactive site loop probably involved in chitin interactions. Taken together, these data suggested that the insecticidal activity of ApKTI for P. interpunctella larvae involves a dual and promiscuous mechanisms biding to two completely different targets. Both processes might impair the P. interpunctella larval digestive process, leading to larvae death before reaching the pupal stage. Further studies are encouraged using ApKTI as a biotechnological tool to control insect pests in field conditions.

Plant Serine Protease Inhibitors: Biotechnology Application in Agriculture and Molecular Farming

The serine protease inhibitors (SPIs) are widely distributed in living organisms like bacteria, fungi, plants, and humans. The main function of SPIs as protease enzymes is to regulate the proteolytic activity. In plants, most of the studies of SPIs have been focused on their physiological role. The initial studies carried out in plants showed that SPIs participate in the regulation of endogenous proteolytic processes, as the regulation of proteases in seeds. Besides, it was observed that SPIs also participate in the regulation of cell death during plant development and senescence. On the other hand, plant SPIs have an important role in plant defense against pests and phytopathogenic microorganisms. In the last 20 years, several transgenic plants over-expressing SPIs have been produced and tested in order to achieve the increase of the resistance against pathogenic insects. Finally, in molecular farming, SPIs have been employed to minimize the proteolysis of recombinant proteins expressed in plants. The present review discusses the potential biotechnological applications of plant SPIs in the agriculture field.

Purification and characterization of Bowman-Birk and Kunitz isoinhibitors from the seeds of Rhynchosia sublobata (Schumach.) Meikle, a wild relative of pigeonpea

Rhynchosia sublobata, a wild relative of pigeonpea, possesses defensive proteinase/protease inhibitors (PIs). Characterization of trypsin specific PIs (RsPI) separated from seeds by column chromatography using 2-D gel electrophoresis and Edman degradation method identified R. sublobata possessed both Bowman-Birk isoinhibitors (RsBBI) and Kunitz isoinhibitors (RsKI). A quick method was developed to separate RsBBI and RsKI from RsPI based on their differential solubility in TCA and acetate buffer. N-terminus sequencing of RsBBI and RsKI by MALDI-ISD ascertained the presence of Bowman Birk and Kunitz type isoinhibitors in R. sublobata. RsBBI (9216 Da) and RsKI (19,412 Da) exhibited self-association pattern as revealed by western blotting with anti-BBI antibody and MALDI-TOF peptide mass fingerprint analysis, respectively. RsBBI and RsKI varied significantly in their biochemical, biophysical and insecticidal properties. RsBBI inhibited the activity of trypsin (Ki = 128.5 ± 4.5 nM) and chymotrypsin (Ki = 807.8 ± 23.7 nM) while RsKI (Ki = 172.0 ± 9.2 nM) inhibited the activity of trypsin alone, by non-competitive mode. The trypsin inhibitor (TI) and chymotrypsin inhibitor (CI) activities of RsBBI were stable up to 100 °C. But, RsBBI completely lost its TI and CI activities on reduction with 3 mM DTT. Conversely, RsKI lost its TI activity on heating at 100 °C and retained >60% of its TI activity in presence of 3 mM DTT. CD spectroscopic studies on RsBBI and RsKI showed their secondary structural elements in the following order: random coils > β-sheets/β-turns > α-helix. However, RsKI showed reversible denaturation midpoint (Tm) of 75 °C. Further, the significant inhibitory activity of RsBBI (IC₅₀ = 24 ng) and RsKI (IC₅₀ = 59 ng) against trypsin-like gut proteases of Achaea janata (AjGPs) and Helicoverpa armigera (HaGPs) suggest them as potential biomolecules in the management of A. janata and H. armigera, respectively.

First insights into insecticidal activity against Aedes aegypti and partial biochemical characterization of a novel low molecular mass chymotrypsin-trypsin inhibitor purified from Lonchocarpus sericeus seeds

BACKGROUND

Arboviroses such as dengue, Zika and chikungunya represent a serious public health issue as a consequence of the absence of approved vaccines or specific antiviral drugs against the arboviruses that cause them. One way to prevent these diseases is by combating the vector mosquito, Aedes aegypti (Diptera), which has serine proteases in the midgut. Protease inhibitors are molecules that can block enzyme activity, impairing digestion and nutrition, which can lead to death. Thus, we purified and characterized a novel chymotrypsin-trypsin inhibitor (LsCTI) from Lonchocarpus sericeus seeds and investigated its effect upon Ae. aegypti egg hatching, larval development and digestive proteases.

RESULTS

LsCTI showed a single protein band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the molecular mass determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was 8870.45 Da. Kinetics analyses revealed a noncompetitive type of inhibition and low inhibition constant (K_i ) for chymotrypsin (8.24 x 10^-8 m). The thermal resistance was remarkable, even at 100 °C for 180 min. The inhibitor concentration required for 50-percent enzyme inhibition (IC₅₀ ) of LsCTI was 4.7 x 10^-7 m for Ae. aegypti midgut larval enzymes. LsCTI did not affect egg hatchability at 0.3 mg mL^-1 , but caused a high larval mortality rate (77%) and delayed development (37%).

CONCLUSIONS

LsCTI is a novel protease inhibitor with remarkable biochemical characteristics and is a potential tool to control Ae. aegypti development. © 2017 Society of Chemical Industry.

Novel Peptidase Kunitz Inhibitor from Platypodium elegans Seeds Is Active against Spodoptera frugiperda Larvae

A novel Kunitz-type inhibitor from Platypodium elegans seeds (PeTI) was purified and characterized. The mass spectrometry analyses of PeTI indicated an intact mass of 19 701 Da and a partial sequence homologous to Kunitz inhibitors. PeTI was purified by ion exchange and affinity chromatographies. A complex with a 1:1 ratio was obtained only for bovine trypsin, showing a K_i = 0.16 nM. Stability studies showed that PeTI was stable over a wide range of temperature (37-80 °C) and pH (2-10). The inhibitory activity of PeTI was affected by dithiothreitol (DTT). Bioassays of PeTI on Spodoptera frugiperda showed negative effects on larval development and weight gain, besides extending the insect life cycle. The activities of digestive enzymes, trypsin and chymotrypsin, were reduced by feeding larvae with 0.2% PeTI in an artificial diet. In summary, we describe a novel Kunitz inhibitor with promising biotechnological potential for pest control.

Physio-chemical Characterization and Anti-microbial Activity of Serine Protease Inhibitors Purified from the Sophora japonica Seeds

BACKGROUND AND OBJECTIVE

Protease inhibitors (PIs) regulate various cellular processes like cell cycle, differentiation, apoptosis and immune responses. Leguminous seeds are rich sources of protease inhibitors and many novel protease inhibitors have been purified from them. To isolate and purify protease inhibitors from seeds of Sophora japonica, characterize and investigate their anti- microbial activity.

MATERIALS AND METHODS

Protease inhibitors (SJ-pi I and SJ-pi II) were purified to homogeneity by ammonium sulfate precipitation, Ion exchange chromatography and column chromatography. The molecular mass was estimated by size exclusion chromatography and by SDS-PAGE and anti- microbial activity was tested by agar disk diffusion method.

RESULTS

Two protease inhibitors were isolated and purified from Sophora japonica seeds, SJ-pi I and SJ-pi II, with molecular weight of 15.1 and 31 kDa, respectively. Both purified inhibitors were active over a range of pH (6.0-9.0) and showed maximum activity in the temperature range of 30-40°C. They inhibited the growth of three Gram-positive bacteria.

CONCLUSION

Protease inhibitors were classified as serine protease inhibitors, however further necessary structural investigations need to be carried out so as to group them into specific class of serine protease inhibitors.

Psc-AFP from Psoralea corylifolia L. overexpressed in Pichia pastoris increases antimicrobial activity and enhances disease resistance of transgenic tobacco

Psc-AFP, isolated from the seeds of Psoralea corylifolia L., is an antimicrobial protein with trypsin inhibitor activity. Its encoding gene was cloned by 3'- rapid amplification of cDNA ends (RACE) combined with Y-shaped adaptor-dependent extension (YADE) method. The gene Psc-AFP encodes a protein of 203 amino acids with a deduced signal peptide of 24 residues. The growth inhibition effect exerted by the heterologously expressed Psc-AFP in Pichia pastoris revealed that the recombinant Psc-AFP inhibited mycelium growth of Aspergillus niger, Rhizoctonia solani, and Alternaria brassicae and conidial germination of Alternaria alternata. The recombinant Psc-AFP also showed protease inhibitor activity manifested by the inhibition of trypsin. The transgenic tobacco bioassays confirmed that overexpressing Psc-AFP significantly enhanced the disease resistance of tobacco and that some of the transgenic lines were almost fully tolerant to Ralstonia solanacearum and A. alternata, whereas no apparent alteration in plant growth and development was observed. Collectively, these results indicate that the recombinant Psc-AFP is an active antimicrobial protein, with protease inhibitor activity that can be successfully produced in the yeast and tobacco and, therefore, maybe a potential antimicrobial candidate for practical use.

Juggling jobs: roles and mechanisms of multifunctional protease inhibitors in plants

Multifunctional protease inhibitors juggle jobs by targeting different enzymes and thereby often controlling more than one biological process. Here, we discuss the biological functions, mechanisms and evolution of three types of multifunctional protease inhibitors in plants. The first type is double-headed inhibitors, which feature two inhibitory sites targeting proteases with different specificities (e.g. Bowman-Birk inhibitors) or even different hydrolases (e.g. α-amylase/protease inhibitors preventing both early germination and seed predation). The second type consists of multidomain inhibitors which evolved by intragenic duplication and are released by processing (e.g. multicystatins and potato inhibitor II, implicated in tuber dormancy and defence, respectively). The third type consists of promiscuous inhibitory folds which resemble mouse traps that can inhibit different proteases cleaving the bait they offer (e.g. serpins, regulating cell death, and α-macroglobulins). Understanding how multifunctional inhibitors juggle biological jobs increases our knowledge of the connections between the networks they regulate. These examples show that multifunctionality evolved independently from a remarkable diversity of molecular mechanisms that can be exploited for crop improvement and provide concepts for protein design.

Cathepsins of lepidopteran insects: Aspects and prospects

Molecular understanding of lepidopteran physiology has revealed that proteases consist of one of the central regulatory/reacting system for insect growth and survival. Among the various proteases, cathepsins are the most crucial cellular proteases, which play vital roles during insect development. In the present review, we have discussed various aspects of the lepidopteran insect cathepsins, emphasizing their roles in processes like development, growth, metamorphosis, apoptosis and immunity. Cathepsins are categorized into different types on the basis of their sequence diversification, leading to variation in structure and catalytic function. Cathepsins exhibit tissue and stage specific expression pattern which is fine-tuned by a delicate balance of expression, compartmentalization, zymogen activation, inhibition by protein inhibitors and degradation. The indispensability of cathepsins as cellular proteases in the above mentioned processes proposes them as novel targets for designing effective and specific insect controlling strategies.

Proteome of Soybean Seed Exudates Contains Plant Defense-Related Proteins Active against the Root-Knot Nematode Meloidogyne incognita

Several studies have described the effects of seed exudates against microorganisms, but only few of them have investigated the proteins that have defensive activity particularly against nematode parasites. This study focused on the proteins released in the exudates of soybean seeds and evaluated their nematicidal properties against Meloidogyne incognita. A proteomic approach indicated the existence of 63 exuded proteins, including β-1,3-glucanase, chitinase, lectin, trypsin inhibitor, and lipoxygenase, all of which are related to plant defense. The presence of some of these proteins was confirmed by their in vitro activity. The soybean exudates were able to reduce the hatching of nematode eggs and to cause 100% mortality of second-stage juveniles (J2). The pretreatment of J2 with these exudates resulted in a 90% reduction of the gall number in tobacco plants. These findings suggest that the exuded proteins are directly involved in plant defense against soil pathogens, including nematodes, during seed germination.

Defense response in non-genomic model species: methyl jasmonate exposure reveals the passion fruit leaves' ability to assemble a cocktail of functionally diversified Kunitz-type trypsin inhibitors and recruit two of them against papain

Multiplicity of protease inhibitors induced by predators may increase the understanding of a plant's intelligent behavior toward environmental challenges. Information about defense mechanisms of non-genomic model plant passion fruit (Passiflora edulis Sims) in response to predator attack is still limited. Here, via biochemical approaches, we showed its flexibility to build-up a broad repertoire of potent Kunitz-type trypsin inhibitors (KTIs) in response to methyl jasmonate. Seven inhibitors (20-25 kDa) were purified from exposed leaves by chromatographic techniques. Interestingly, the KTIs possessed truncated Kunitz motif in their N-terminus and some of them also presented non-consensus residues. Gelatin-Native-PAGE established multiple isoforms for each inhibitor. Significant differences regarding inhibitors' activity toward trypsin and chymotrypsin were observed, indicating functional polymorphism. Despite its rarity, two of them also inhibited papain, and such bifunctionality suggests a recruiting process onto another mechanistic class of target protease (cysteine-type). All inhibitors acted strongly on midgut proteases from sugarcane borer, Diatraea saccharalis (a lepidopteran insect) while in vivo assays supported their insecticide properties. Moreover, the bifunctional inhibitors displayed activity toward midgut proteases from cowpea weevil, Callosobruchus maculatus (a coleopteran insect). Unexpectedly, all inhibitors were highly effective against midgut proteases from Aedes aegypti a dipteran insect (vector of neglected tropical diseases) opening new avenues for plant-derived PIs for vector control-oriented research. Our results reflect the KTIs' complexities in passion fruit which could be wisely exploited by influencing plant defense conditions. Therefore, the potential of passion fruit as source of bioactive compounds with diversified biotechnological application was strengthened.

Short and long-term antinutritional effect of the trypsin inhibitor ApTI for biological control of sugarcane borer

Plant-derived trypsin inhibitors have been shown to have potent anti-insect effects and are a promising alternative for the biological control of pests. In this work, we tested the anti-insect activity of Adenanthera pavonina trypsin inhibitor (ApTI) against Diatraea saccharalis larvae, a major insect pest in sugarcane. The addition of 0.1% ApTI in short-term assays resulted in 87% and 63% decreased trypsin and chymotrypsin activities respectively. ApTI was not digested after 60h incubation with D. saccharalis midgut proteases. The chronic effects of ApTI on F0 and F1 generations of D. saccharalis were also analyzed. The larvae from the F0 generation showed 55% and 21% decreased larval and pupal viability, respectively. ApTI-fed larvae from the F1 generation showed a decrease of 33% in survival rate and 23% in the average larval weight. Moreover, ApTI treatment reduced trypsin and chymotrypsin activities in F1 larvae. Thus, the anti-insect effects of ApTI on consecutive generations (F0 and F1) of D. saccharalis larvae demonstrate its potential for long-term control of this pest.

Effects of the aspartic protease inhibitor from Lupinus bogotensis seeds on the growth and development of Hypothenemus hampei: an inhibitor showing high homology with storage proteins

The coffee berry borer Hypothenemus hampei is a pest that causes great economic damage to coffee grains worldwide. Because the proteins consumed are digested by aspartic proteases in the insect's midgut, the inhibition of these proteases by transferring a gene encoding an aspartic protease inhibitor from Lupinus bogotensis Benth. to coffee plants could provide a promising strategy to control this pest. Five aspartic protease inhibitors from L. bogotensis (LbAPI) were accordingly purified and characterized. The gene encoding the L. bogotensis aspartic protease inhibitor (LbAPI), with the highest inhibitory activity against H. hampei, was expressed in Escherichia coli and the purified recombinant protein (rLbAPI), with a molecular mass of 15 kDa, was subsequently assessed for its ability to inhibit the aspartic protease activity present in the H. hampei midgut in vitro, as well as its effects on the growth and development of H. hampei in vivo. The in vitro experiments showed that rLbAPI was highly effective against aspartic proteases from H. hampei guts, with a half maximal inhibitory concentration (IC50) of 2.9 μg. The in vivo experiments showed that the concentration of rLbAPI (w/w) in the artificial diet necessary to cause 50% mortality (LD50) of the larvae was 0.91%. The amino acid sequence of LbAPI had high homology (52-80%) to the seed storage proteins, vicilin and β-conglutin, suggesting that this protein was generated by evolutionary events from a β-conglutin precursor. Based on these results, LbAPI may have a dual function as storage protein, and as defense protein against H. hampei. These results provide a promising alternative to obtain a coffee plant resistant to H. hampei.

Biochemical responses of Anticarsia gemmatalis (Lepidoptera: Noctuidae) in soybean cultivars sprayed with the protease inhibitor berenil

The damage caused by Anticarsia gemmatalis motivates this study on the adaptive mechanisms of the insect to soybean. The lipoxygenase pathway produces and releases jasmonic acid, involved in the regulation of the plant defense genes, which encodes protease inhibitor (PI) production. Three soybean cultivars IAC-18, IAC-24, and Foscarin-31 were sprayed with water and berenil, a synthetic inhibitor, at 0.60 and 1.0% (w/v) and then infested with A. gemmatalis larvae. The lipoxygenase (LOX) activity increased in the leaves of Foscarin-31, IAC-18, and IAC-24 by 87, 81, and 78%, respectively, after 24 h of A. gemmatalis damage. IAC-18 revealed the lowest increase in PI when compared to the other cultivars. Protease, amidase, and esterase activities in soybean larvae dropped drastically after berenil application. PIs may be included in the control strategies of A. gemmatalis in soybean by lowering the digestive enzyme activity in the larval midgut, thus affecting insect growth and development.

Molecular dynamics and free energy studies on the carboxypeptidases complexed with peptide/small molecular inhibitor: mechanism for drug resistance

As one potent plant protease inhibitor, potato carboxypeptidase inhibitor (PCI) can competitively inhibit insect digestive metallocarboxypeptidases (MCPs) through interfering with its digestive system that causes amino acid deficiencies and leading to serious developmental delay and mortality. However, this effective biological pest control is significantly impaired by the PCI-resistant insect MCPs. Therefore, deep understanding of the resistant mechanism of insect MCPs is particularly necessary for designing new durable pest control regimen and developing effective pesticides. In this study, the binding of PCI and small molecular inhibitor THI to insect PCI-sensitive/-resistant MCPs and human MCP was investigated by docking, molecular dynamics (MD) simulations and thermodynamic analysis. The structural analysis from MD simulations indicates that the PCI-resistant mechanism of CPBHz is mainly dominated by the Trp277A, which changes the conformation of β8-α9 loop and therefore narrow the access to the active site of CPBHz, prohibiting the entrance of the C termini tail of PCI. Additionally, the insertion of Gly247A weakens the stabilization of CPBHz and PCI through disrupting the hydrogen bond formation with its surrounding residues. Furthermore, the predicted binding free energies gives explanation of structure affinity relationship of PCI and THI with MCPs and suggest that the electrostatic energy is the main contribution term affecting the difference in binding affinities. Finally, the decomposition analysis of binding free energies infers that the key residues Glu72, Arg127, Ile247/Leu247 and Glu270 are critical for the binding of PCI/THI to MCPs.

Structural insights regarding an insecticidal Talisia esculenta protein and its biotechnological potential for Diatraea saccharalis larval control

Talisin is a seed-storage protein from Talisia esculenta that presents lectin-like activities, as well as proteinase-inhibitor properties. The present study aims to provide new in vitro and in silico biochemical information about this protein, shedding some light on its mechanistic inhibitory strategies. A theoretical three-dimensional structure of Talisin bound to trypsin was constructed in order to determine the relative interaction mode. Since the structure of non-competitive inhibition has not been elucidated, Talisin-trypsin docking was carried out using Hex v5.1, since the structure of non-competitive inhibition has not been elucidated. The predicted non-coincidence of the trypsin binding site is completely different from that previously proposed for Kunitz-type inhibitors, which demonstrate a substitution of an Arg(64) for the Glu(64) residue. Data, therefore, provide more information regarding the mechanisms of non-competitive plant proteinase inhibitors. Bioassays with Talisin also presented a strong insecticide effect on the larval development of Diatraea saccharalis, demonstrating LD50 and ED50 of ca. 2.0% and 1.5%, respectively.

Plant storage proteins with antimicrobial activity: novel insights into plant defense mechanisms

Storage proteins perform essential roles in plant survival, acting as molecular reserves important for plant growth and maintenance, as well as being involved in defense mechanisms by virtue of their properties as insecticidal and antimicrobial proteins. These proteins accumulate in storage vacuoles inside plant cells, and, in response to determined signals, they may be used by the different plant tissues in response to pathogen attack. To shed some light on these remarkable proteins with dual functions, storage proteins found in germinative tissues, such as seeds and kernels, and in vegetative tissues, such as tubercles and leaves, are extensively discussed here, along with the related mechanisms of protein expression. Among these proteins, we focus on 2S albumins, Kunitz proteinase inhibitors, plant lectins, glycine-rich proteins, vicilins, patatins, tarins, and ocatins. Finally, the potential use of these molecules in development of drugs to combat human and plant pathogens, contributing to the development of new biotechnology-based medications and products for agribusiness, is also presented.