Aspartic Protease Research Articles

Improving Gelling Properties of Tofu: Study on ApnA Aspartic Protease Enzyme Impact on the Resulting Chemical and Microstructure Properties

Improving Gelling Properties of Tofu: Study on ApnA Aspartic Protease Enzyme Impact on the Resulting Chemical and Microstructure Properties

Nelfinavir inhibition of Kaposi’s sarcoma-associated herpesvirus protein expression and capsid assembly

BackgroundAntiviral therapies that target herpesviruses are clinically important. Nelfinavir is a protease inhibitor that targets the human immunodeficiency virus (HIV) aspartyl protease. Previous studies demonstrated that this drug could also inhibit Kaposi’s sarcoma-associated herpesvirus (KSHV) production. Our laboratory demonstrated nelfinavir can effectively inhibit herpes simplex virus type 1 (HSV-1) replication. For HSV-1 we were able to determine that virus capsids were assembled and exited the nucleus but did not mature in the cytoplasm indicating the drug inhibited secondary envelopment of virions.MethodsFor KSHV, we recently derived a tractable cell culture system that allowed us to analyze the virus replication cycle in greater detail. We used this system to further define the stage at which nelfinavir inhibits KSHV replication.ResultsWe discovered that nelfinavir inhibits KSHV extracellular virus production. This was seen when the drug was incubated with the cells for 3 days and when we pulsed the cells with the drug for 1–5 min. When KSHV infected cells exposed to the drug were examined using ultrastructural methods there was an absence of mature capsids in the nucleus indicating a defect in capsid assembly. Because nelfinavir influences the integrated stress response (ISR), we examined the expression of viral proteins in the presence of the drug. We observed that the expression of many were significantly changed in the presence of drug. The accumulation of the capsid triplex protein, ORF26, was markedly reduced. This is an essential protein required for herpesvirus capsid assembly.ConclusionsOur studies confirm that nelfinavir inhibits KSHV virion production by disrupting virus assembly and maturation. This is likely because of the effect of nelfinavir on the ISR and thus protein synthesis and accumulation of the essential triplex capsid protein, ORF26. Of interest is that inhibition requires only a short exposure to drug. The source of infectious virus in saliva has not been defined in detail but may well be lymphocytes or other cells in the oral mucosa. Thus, it might be that a “swish and spit” exposure rather than systemic administration would prevent virion production.

Cathepsin D inhibition during neuronal differentiation selectively affects individual proteins instead of overall protein turnover

Cathepsin D (CTSD) is a lysosomal aspartic protease and its inherited deficiency causes a severe pediatric neurodegenerative disease called neuronal ceroid lipofuscinosis (NCL) type 10. The lysosomal dysfunction in the affected patients leads to accumulation of undigested lysosomal cargo especially in none-dividing cells, such as neurons, resulting in death shortly after birth. To explore which proteins are mainly affected by the lysosomal dysfunction due to CTSD deficiency, Lund human mesencephalic (LUHMES) cells, capable of inducible dopaminergic neuronal differentiation, were treated with Pepstatin A. This inhibitor of “acidic” aspartic proteases caused accumulation of acidic intracellular vesicles in differentiating LUHMES cells. Pulse-chase experiments involving stable isotope labelling with amino acids in cell culture (SILAC) with subsequent mass-spectrometric protein identification and quantification were performed. By this approach, we studied the degradation and synthesis rates of 695 and 680 proteins during early and late neuronal LUHMES differentiation, respectively. Interestingly, lysosomal bulk proteolysis was not altered upon Pepstatin A treatment. Instead, the protease inhibitor selectively changed the turnover of individual proteins. Especially proteins belonging to the mitochondrial energy supply system were differentially degraded during early and late neuronal differentiation indicating a high energy demand as well as stress level in LUHMES cells treated with Pepstatin A.

Aspartyl proteases identified as candidate genes of a fiber length QTL, qFLD05, that regulates fiber length in cotton (Gossypium hirsutum L.).

GhAP genes were identified as the candidates involved in cotton fiber length under the scope of fine mapping a stable fiber length QTL, qFLD05. Moreover, the transcription factor GhWRKY40 positively regulated GhAP3 to decrease fiber length. Fiber length (FL) is an economically important fiber quality trait. Although several genes controlling cotton fiber development have been identified, our understanding of this process remains limited. In this study, an FL QTL (qFLD05) was fine-mapped to a 216.9-kb interval using a secondary F2:3 population derived from the upland hybrid cultivar Ji1518. This mapped genomic segment included 15 coding genes, four of which were annotated as aspartyl proteases (GhAP1-GhAP4). GhAPs were identified as candidates for qFLD05 as the sequence variations in GhAPs were associated with FL deviations in the mapping population, and functional validation of GhAP3 and GhAP4 indicated a longer FL following decreases in their expression levels through virus-induced gene silencing (VIGS). Subsequently, the potential involvement of GhWRKY40 in the regulatory network was revealed: GhWRKY40 positively regulated GhAP3's expression according to transcriptional profiling, VIGS, yeast one-hybrid assays and dual-luciferase experiments. Furthermore, alterations in the expression of the eight previously reported cotton FL-responsive genes from the above three VIGS lines (GhAP3, GhAP4 and GhWRKY40) implied that MYB5_A12 was involved in the GhWRKY40-GhAP network. In short, we unveiled the unprecedented FL regulation roles of GhAPs in cotton, which was possibly further regulated by GhWRKY40. These findings will reveal the genetic basis of FL development associated with qFLD05 and be beneficial for the marker-assisted selection of long-staple cotton.

Prodomain-driven enzyme dimerization: a pH-dependent autoinhibition mechanism that controls Plasmodium Sub1 activity before merozoite egress.

Malaria symptoms are associated with the asexual multiplication of Plasmodium falciparum within human red blood cells (RBCs) and fever peaks coincide with the egress of daughter merozoites following the rupture of the parasitophorous vacuole (PV) and the RBC membranes. Over the last two decades, it has emerged that the release of competent merozoites is tightly regulated by a complex cascade of events, including the unusual multi-step activation mechanism of the pivotal subtilisin-like protease 1 (Sub1) that takes place in three different cellular compartments and remains poorly understood. Following an initial auto-maturation in the endoplasmic reticulum (ER) between its pro- and catalytic domains, the Sub1 prodomain (PD) undergoes further cleavages by the parasite aspartic protease plasmepsin X (PmX) within acidic secretory organelles that ultimately lead to full Sub1 activation upon discharge into the PV. Here, we report the crystal structure of full-length P. falciparum Sub1 (PfS1FL) and demonstrate, through structural, biochemical, and biophysical studies, that the atypical Plasmodium-specific Sub1 PD directly promotes the assembly of inactive enzyme homodimers at acidic pH, whereas Sub1 is primarily monomeric at neutral pH. Our results shed new light into the finely tuned Sub1 spatiotemporal activation during secretion, explaining how PmX processing and full activation of Sub1 can occur in different cellular compartments, and uncover a robust mechanism of pH-dependent subtilisin autoinhibition that plays a key role in P. falciparum merozoites egress from infected host cells.IMPORTANCEMalaria fever spikes are due to the rupture of infected erythrocytes, allowing the egress of Plasmodium sp. merozoites and further parasite propagation. This fleeting tightly regulated event involves a cascade of enzymes, culminating with the complex activation of the subtilisin-like protease 1, Sub1. Differently than other subtilisins, Sub1 activation strictly depends upon the processing by a parasite aspartic protease within acidic merozoite secretory organelles. However, Sub1 biological activity is required in the pH neutral parasitophorous vacuole, to prime effectors involved in the rupture of the vacuole and erythrocytic membranes. Here, we show that the unusual, parasite-specific Sub1 prodomain is directly responsible for its acidic-dependent dimerization and autoinhibition, required for protein secretion, before its full activation at neutral pH in a monomeric form. pH-dependent Sub1 dimerization defines a novel, essential regulatory element involved in the finely tuned spatiotemporal activation of the egress of competent Plasmodium merozoites.

Toxoplasma gondii aspartic protease 5: structural basis of substrate binding and inhibition mechanism

Toxoplasma gondii, a worldwide prevalent parasite is responsible for causing toxoplasmosis in almost all warm-blooded animals, including humans. Golgi-resident T. gondii aspartic protease 5 (TgASP5) plays an essential role in the maturation and export of the effector proteins those modulate the host immune system to establish a successful infection. Hence, inhibiting this enzyme can be a possible therapeutic strategy against toxoplasmosis. This is the first report of the detailed structural investigations of the TgASP5 mature enzyme using molecular modeling and an all-atom simulation approach which provide in-depth knowledge of the active site architecture of TgASP5. The analysis of the binding mode of the TEXEL (Toxoplasma EXport Element) substrate to TgASP5 highlighted the importance of the active site residues. Ser505, Ala776 and Tyr689 in the S2 binding pocket are responsible for the specificity towards Arg at the P2 position of TEXEL substrate. The molecular basis of inhibition by the only known inhibitor RRLStatine has been identified, and our results show that it blocks the active site by forming a hydrogen bond with a catalytic aspartate. Besides that, known aspartic protease inhibitors were screened against TgASP5 using docking, MD simulations and MM-PBSA binding energy calculations. The top-ranked inhibitors (SC6, ZY1, QBH) showed higher binding energy than RRLStatine. Understanding the structural basis of substrate recognition and the binding mode of these inhibitors will help to develop potent mechanistic inhibitors against TgASP5. This study will also provide insights into the structural features of pepsin-like aspartic proteases from other apicomplexan parasites for developing antiparasitic agents. Communicated by Ramaswamy H. Sarma

Preclinical characterization of a non-peptidomimetic HIV protease inhibitor with improved metabolic stability.

Protease inhibitors (PIs) remain an important component of antiretroviral therapy for the treatment of HIV-1 infection due to their high genetic barrier to resistance development. Nevertheless, the two most commonly prescribed HIV PIs, atazanavir and darunavir, still require co-administration with a pharmacokinetic boosting agent to maintain sufficient drug plasma levels which can lead to undesirable drug-drug interactions. Herein, we describe GS-9770, a novel investigational non-peptidomimetic HIV PI with unboosted once-daily oral dosing potential due to improvements in its metabolic stability and its pharmacokinetic properties in preclinical animal species. This compound demonstrates potent inhibitory activity and high on-target selectivity for recombinant HIV-1 protease versus other aspartic proteases tested. In cell culture, GS-9770 inhibits Gag polyprotein cleavage and shows nanomolar anti-HIV-1 potency in primary human cells permissive to HIV-1 infection and against a broad range of HIV subtypes. GS-9770 demonstrates an improved resistance profile against a panel of patient-derived HIV-1 isolates with resistance to atazanavir and darunavir. In resistance selection experiments, GS-9770 prevented the emergence of breakthrough HIV-1 variants at all fixed drug concentrations tested and required multiple protease substitutions to enable outgrowth of virus exposed to escalating concentrations of GS-9770. This compound also remained fully active against viruses resistant to drugs from other antiviral classes and showed no in vitro antagonism when combined pairwise with drugs from other antiretroviral classes. Collectively, these preclinical data identify GS-9770 as a potent, non-peptidomimetic once-daily oral HIV PI with potential to overcome the persistent requirement for pharmacological boosting with this class of antiretroviral agents.

Correlation of Experimental and Calculated Inhibition Constants of Protease Inhibitor Complexes.

Predicting the potency of inhibitors is key to in silico screening of promising synthetic or natural compounds. Here we describe a predictive workflow that provides calculated inhibitory values, which concord well with empirical data. Calculations of the free interaction energy ΔG with the YASARA plugin FoldX were used to derive inhibition constants Ki from PDB coordinates of protease-inhibitor complexes. At the same time, corresponding KD values were obtained from the PRODIGY server. These results correlated well with the experimental values, particularly for serine proteases. In addition, analyses were performed for inhibitory complexes of cysteine and aspartic proteases, as well as of metalloproteases, whereby the PRODIGY data appeared to be more consistent. Based on our analyses, we calculated theoretical Ki values for trypsin with sunflower trypsin inhibitor (SFTI-1) variants, which yielded the more rigid Pro14 variant, with probably higher potency than the wild-type inhibitor. Moreover, a hirudin variant with an Arg1 and Trp3 is a promising basis for novel thrombin inhibitors with high potency. Further examples from antibody interaction and a cancer-related effector-receptor system demonstrate that our approach is applicable to protein interaction studies beyond the protease field.

Phytochemical Characterization, Antimicrobial Activity, Pharmacokinetic,in silicoMolecular Docking and Interaction Analysis of Ajwa (Phoenix dactyliferaL.) Palm Date Seeds

BackgroundThere is growing evidence that antibiotic resistance is increasing. As a result, the efficacy of these antibiotics is gradually declining. This poses a serious health risk in terms of treatment strategies. Therefore, the scientific community is continuously putting all efforts into looking for novel and green therapeutics to overcome the problem of antibiotic resistance.ObjectivesThe aim of this study is to investigate the chemical composition of the methanolic extracts obtained from Phoenix dactylifera seeds, known agricultural waste, to identify new bioactive compounds and to examine the antibacterial and antifungal potentials.Materials and MethodsPhytochemical profiling was performed by the gas chromatography-mass spectrometry (GC-MS) technique. For the antibacterial activity of the methanolic extract, 12 microorganisms were selected, including eight bacteria ( Escherichia coli ATCC 35218, Pseudomonas aeruginosa ATCC 27853, Enterobacter cloacae, Enterococcus faecium, Staphylococcus hominis, Staphylococcus aureus, Staphylococcus epidermidis, and Klebsiella pneumoniae ATCC 27736) and four Candida species (C. albicans ATCC 10231, C. tropicalis ATCC 1362, C. utilis ATCC 9255, and C. guilliermondii ATCC 6260). The antimicrobial activity of the plant extract was supported by in silico molecular docking analysis.ResultsThe obtained results from the GC-MS technique revealed the presence of 51 compounds, of which 6-octadecenoic acid (Z) was identified as the major component. The tested extract exhibited the highest zone of inhibition against S. aureus (growth inhibition zone 14.66 ± 0.57 mm). In addition, minimal inhibitory concentration (MIC) and minimal bactericidal concentration values obtained against S. aureus were 1.4 and 5.6 mg/mL, respectively. Regarding the antifungal assay, C. albicans was the most sensitive one to the extract among all the tested Candida strains (14.33 mm) (MIC: 1.4 mg/mL, minimal fungicidal concentration (MFC): 11.2 mg/mL). The binding free energies and root mean square deviation values obtained from the interaction of phytochemicals with two different target receptors (1JIJ and 2QZW for TyrRS from S. aureus and aspartic proteinase from C. albicans) were also determined. Ergost-5-en-3-ol, (3beta) established hydrogen, electrostatic, alkyl, and pi-alkyl interactions with five different amino acid residues (Asp40, Asp80, Pro53, His50, and Phe54) located at the TyrRS receptor of S. aureus. On the other hand, hexadecanoic acid and methyl ester established hydrogen, electrostatic, pi-sigma, and alkyl interactions with five different amino acid residues (Thr222, Asp86, Asp218, Tyr84, and Ile123) located at the aspartic proteinase receptor of C. albicans. These interactions contributed to the stability of the complex and, hence, to the biological activity of the P. dactylifera compounds.ConclusionOur results highlighted that methanolic extract from date seeds can be a natural source of chemical compounds with promising antibacterial and antifungal activities, as demonstrated using both in vitro and in silico approaches.

CG-MS, Radical Scavenging, Acetylcholinesterase Inhibition, Antifungal and Molecular Docking Studies of Essential Oil from the Leaves of Tapirira guianensis Aubl

The species Tapirira guianensis Aubl is used in folk medicine to treat leprosy, diarrhea, and syphilis. The present study aims to evaluate the chemical composition and the antioxidant, anticholinesterase, and antifungal potential of the essential oil from T. guianensis leaves. The plant material was collected at Arco Estadual do Cocó, with prior authorization from the Municipal Environment Department. The essential oil was extracted through the hydrodistillation process with a Clevenger-type apparatus, and the constituents were evaluated through Gas Chromatography coupled to Mass Spectrometry (GC-MS). The antioxidant potential was assessed through free radicals: DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS+ (2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) in a 96-well plate. Antifungal activity was evaluated using the Clinical Laboratory Standards Institute - M38-A protocol (CLSI, 2018). Gas chromatography coupled with mass spectrometry revealed the presence of constituents such as eugenol (59.00%), α-copaene (0.40%), β-caryophyllene (29.91%), α-humulene in T. guianensis. The essential oil demonstrated very promising antioxidant and anticholinesterase potential in In vitro studies. Molecular docking regarding acetylcholinesterase enzyme inhibition revealed that α-copaene has superior action compared to the drug physostigmine. The results of molecular docking for Candida albicans showed that α-copaene and α-humulene interacted in the same binding region as the PepA inhibitor against SAP5. This indicates their action is similar to the aspartic protease inhibitor, in addition to the possibility of a synergistic effect with the drug fluconazole. This is the first study of the biological potential of the essential oil from T. guianensis leaves, thus revealing its high potential for future studies in the scientific community. Therefore, we can infer that the essential oil of T. guianensis is a source of antioxidant, anticholinesterase, and antifungal constituents, with promising therapeutic potential in the management of Alzheimer's disease and Candida infections.

Aspartyl protease in the secretome of honey bee trypanosomatid parasite contributes to infection of bees

BackgroundThe exoproteome, which consists of both secreted proteins and those originating from cell surfaces and lysed cells, is a critical component of trypanosomatid parasites, facilitating interactions with host cells and gut microbiota. However, its specific roles in the insect hosts of these parasites remain poorly understood.MethodsWe conducted a comprehensive characterization of the exoproteome in Lotmaria passim, a trypanosomatid parasite infecting honey bees, under culture conditions. We further investigated the functions of two conventionally secreted proteins, aspartyl protease (LpAsp) and chitinase (LpCht), as representative models to elucidate the role of the secretome in L. passim infection of honey bees.ResultsApproximately 48% of L. passim exoproteome proteins were found to share homologs with those found in seven Leishmania spp., suggesting the existence of a core exoproteome with conserved functions in the Leishmaniinae lineage. Bioinformatics analyses suggested that the L. passim exoproteome may play a pivotal role in interactions with both the host and its microbiota. Notably, the deletion of genes encoding two secretome proteins revealed the important role of LpAsp, but not LpCht, in L. passim development under culture conditions and its efficiency in infecting the honey bee gut.ConclusionsOur results highlight the exoproteome as a valuable resource for unraveling the mechanisms employed by trypanosomatid parasites to infect insect hosts by interacting with the gut environment.Graphical

PEXEL is a proteolytic maturation site for both exported and non-exported Plasmodium proteins.

Obligate intracellular malaria parasites dramatically remodel their erythrocyte host through effector protein export to create a niche for survival. Most exported proteins contain a pentameric Plasmodium export element (PEXEL)/host-targeting motif that is cleaved in the parasite ER by the aspartic protease Plasmepsin V (PMV). This processing event exposes a mature N terminus required for translocation into the host cell and is not known to occur in non-exported proteins. Here, we report that the non-exported parasitophorous vacuole protein UIS2 contains a bona fide PEXEL motif that is processed in the P. falciparum blood stage. While the N termini of exported proteins containing the PEXEL and immediately downstream ~10 residues are sufficient to mediate translocation into the RBC, the equivalent UIS2 N terminus does not promote the export of a reporter. Curiously, the UIS2 PEXEL contains an unusual aspartic acid at the fourth position, which constitutes the extreme N-terminal residue following PEXEL cleavage (P1', RIL↓DE). Using a series of chimeric reporter fusions, we show that Asp at P1' is permissive for PMV processing but abrogates export. Moreover, mutation of this single UIS2 residue to alanine enables export, reinforcing that the mature N terminus mediates export, not PEXEL processing per se. Prompted by this observation, we further show that PEXEL sequences in the N termini of other non-exported rhoptry proteins are also processed, suggesting that PMV may be a more general secretory maturase than previously appreciated, similar to orthologs in related apicomplexans. Our findings provide new insight into the unique N-terminal constraints that mark proteins for export.IMPORTANCEHost erythrocyte remodeling by malaria parasite-exported effector proteins is critical to parasite survival and disease pathogenesis. In the deadliest malaria parasite Plasmodium falciparum, most exported proteins undergo proteolytic maturation via recognition of the pentameric Plasmodium export element (PEXEL)/host-targeting motif by the aspartic protease Plasmepsin V, which exposes a mature N terminus that is conducive for export into the erythrocyte host cell. While PEXEL processing is considered a unique mark of exported proteins, we demonstrate that PEXEL motifs are present and processed in non-exported proteins. Importantly, we show that specific residues at the variable fourth position of the PEXEL motif inhibit export despite being permissive for processing, reinforcing that features of the mature N terminus, and not PEXEL cleavage, identify cargo for export. This opens the door to further inquiry into the nature and evolution of the PEXEL motif.

Silkworm pupae protein co-degradation by magnetic nanoparticles immobilized proteinase K and Mucor circinelloides aspartic protease for further utilization of sericulture by-products

Silkworm pupae, by-product of sericulture industry, is massively discarded. The degradation rate of silkworm pupae protein is critical to further employment, which reduces the impact of waste on the environment. Herein, magnetic Janus mesoporous silica nanoparticles immobilized proteinase K mutant T206M and Mucor circinelloides aspartic protease were employed in the co-degradation. The thermostability of T206M improved by enhancing structural rigidity (t1/2 by 30 min and T50 by 5 °C), prompting the degradation efficiency. At 65 °C and pH 7, degradation rate reached the highest of 61.7%, which improved by 26% compared with single free protease degradation. Besides, the immobilized protease is easy to separate and reuse, which maintains 50% activity after 10 recycles. Therefore, immobilized protease co-degradation was first applied to the development and utilization of silkworm pupae resulting in the release of promising antioxidant properties and reduces the environmental impact by utilizing a natural and renewable resource.

The role of adenocarcinoma subtypes and immunohistochemistry in predicting lymph node metastasis in early invasive lung adenocarcinoma

BackgroundIdentifying lymph node metastasis areas during surgery for early invasive lung adenocarcinoma remains challenging. The aim of this study was to develop a nomogram mathematical model before the end of surgery for predicting lymph node metastasis in patients with early invasive lung adenocarcinoma.MethodsIn this study, we included patients with invasive lung adenocarcinoma measuring ≤ 2 cm who underwent pulmonary resection with definite pathology at Qilu Hospital of Shandong University from January 2020 to January 2022. Preoperative biomarker results, clinical features, and computed tomography characteristics were collected. The enrolled patients were randomized into a training cohort and a validation cohort in a 7:3 ratio. The training cohort was used to construct the predictive model, while the validation cohort was used to test the model independently. Univariate and multivariate logistic regression analyses were performed to identify independent risk factors. The prediction model and nomogram were established based on the independent risk factors. Recipient operating characteristic (ROC) curves were used to assess the discrimination ability of the model. Calibration capability was assessed using the Hosmer–Lemeshow test and calibration curves. The clinical utility of the nomogram was assessed using decision curve analysis (DCA).ResultsThe overall incidence of lymph node metastasis was 13.23% (61/461). Six indicators were finally determined to be independently associated with lymph node metastasis. These six indicators were: age (P < 0.001), serum amyloid (SA) (P = 0.008); carcinoma antigen 125 (CA125) (P = 0. 042); mucus composition (P = 0.003); novel aspartic proteinase of the pepsin family A (Napsin A) (P = 0.007); and cytokeratin 5/6 (CK5/6) (P = 0.042). The area under the ROC curve (AUC) was 0.843 (95% CI: 0.779–0.908) in the training cohort and 0.838 (95% CI: 0.748–0.927) in the validation cohort. the P-value of the Hosmer–Lemeshow test was 0.0613 in the training cohort and 0.8628 in the validation cohort. the bias of the training cohort corrected C-index was 0.8444 and the bias-corrected C-index for the validation cohort was 0.8375. demonstrating that the prediction model has good discriminative power and good calibration.ConclusionsThe column line graphs created showed excellent discrimination and calibration to predict lymph node status in patients with ≤ 2 cm invasive lung adenocarcinoma. In addition, the predictive model has predictive potential before the end of surgery and can inform clinical decision making.

Discovery of Repurposable Drugs in the Combination Therapy of Breast Cancer: A Virtual Drug Screening Study

Cathepsin D (Cat D) is a lysosomal aspartic acid protease encoded by CTSD gene and has significant biological roles such as degradation of extracellular and intracellular proteins, regulation of apoptosis, hormone processing, antigen processing etc. Furthermore, it is overexpressed by breast cancer cells and it acts a role in many processes affecting the cancer prognosis such as metastasis, angiogenesis, invasion, and drug resistance through regulation of the metabolic pathways and digesting the extracellular matrix (ECM) proteins. Due to that there is no drug targeting Cat D in clinical trial phases, a virtual drug screening in order to reveal possible drugs with high Cat D inhibitory activity from a library composed of 12,111 ligands is carried out with this study. Results have demonstrated that ZINC000003922429 (Adozelesin), ZINC000012358610 (Phthalocyanine), ZINC000051951669 (Bemcentinib), ZINC000003786250 (YM022), and ZINC000150338819 (Ledipasvir) have high binding affinity to Cat D. Among these chemical ligands, YM022 from Drugs in Clinical Trials dataset has been evaluated as most promising one that might be repurposed in the treatment of breast cancer due to its high affinity, convenient ADME and Toxicity properties, and highest bioactivity profiles. However, the possible activity of YM022 should be analyzed with further molecular dynamics (MD) simulations, in vitro and in vivo studies.

Characterization of a novel aspartic protease from Trichoderma asperellum for the preparation of duck blood peptides

A novel aspartic protease gene (TaproA1) from Trichoderma asperellum was successfully expressed in Komagataella phaffii (Pichia pastoris). TaproA1 showed 52.8% amino acid sequence identity with the aspartic protease PEP3 from Coccidioides posadasii C735. TaproA1 was efficiently produced in a 5 L fermenter with a protease activity of 4092 U/mL. It exhibited optimal reaction conditions at pH 3.0 and 50 °C and was stable within pH 3.0–6.0 and at temperatures up to 45 °C. The protease exhibited broad substrate specificity with high hydrolysis activity towards myoglobin and hemoglobin. Furthermore, duck blood proteins (hemoglobin and plasma protein) were hydrolyzed by TaproA1 to prepare bioactive peptides with high ACE inhibitory activity. The IC50 values of hemoglobin and plasma protein hydrolysates from duck blood proteins were 0.105 mg/mL and 0.091 mg/mL, respectively. Thus, the high yield and excellent biochemical characterization of TaproA1 presented here make it a potential candidate for the preparation of duck blood peptides.Key points• An aspartic protease (TaproA1) from Trichoderma asperellum was expressed in Komagataella phaffii.• TaproA1 exhibited broad substrate specificity and the highest activity towards myoglobin and hemoglobin.• TaproA1 has great potential for the preparation of bioactive peptides from duck blood proteins.

Integrated proteome and physiological traits reveal interactive mechanisms of new leaf growth and storage protein degradation with mature leaves of evergreen citrus trees.

The growth of fruit trees depends on the nitrogen (N) remobilization in mature tissues and N acquisition from the soil. However, in evergreen mature citrus (Citrus reticulata Blanco) leaves, proteins with N storage functions and hub molecules involved in driving N remobilization remain largely unknown. Here, we combined proteome and physiological analyses to characterize the spatiotemporal mechanisms of growth of new leaves and storage protein degradation in mature leaves of citrus trees exposed to low-N and high-N fertilization in the field. Results show that the growth of new leaves is driven by remobilization of stored reserves, rather than N uptake by the roots. In this context, proline and arginine in mature leaves acted as N sources supporting the growth of new leaves in spring. Time-series analyses with gel electrophoresis and proteome analysis indicated that the mature autumn shoot leaves are probably the sites of storage protein synthesis, while the aspartic endopeptidase protein is related to the degradation of storage proteins in mature citrus leaves. Furthermore, bioinformatic analysis based on protein-protein interactions indicated that glutamate synthetase and ATP-citrate synthetase are hub proteins in N remobilization from mature citrus leaves. These results provide strong physiological data for seasonal optimization of N fertilizer application in citrus orchards.

Characterization of rice aspartic protease genes and induced expression by phytohormones and Xanthomonas oryzae pv. oryzae

Aspartic proteases (APs) are present in both monocotyledonous and dicotyledonous plants. APs consist of nine different families of proteolytic enzymes. APs play important functions in several physiological processes including defense. However, there are limited reports on APs in disease resistance in rice (Oryza sativa). Here, we report that 104 APs were discovered in rice genome. They can be classified into three clades (I, II and III) with APs from Arabidopsis thaliana, and Nymphaea colorata according to phylogenetic relationships. Tandem and segmental duplications were observed to lead to the expansion of OsAP genes in rice. Analysis of gene structure revealed that numerous OsAPs contain multiple exons and introns, however, several OsAPs harbor a single exon and no introns. Synteny analyses demonstrated that four AP genes among O. sativa, A. thaliana, and N. colorata may evolve from a common ancestor of land plants. Ten conserved motifs of amino acids were uncovered from the OsAPs, and two of the motifs are the catalytic sequences, with the conserved Asp-Thr and Ser-Gly amino acids. Within the OsAP promoter sequences, cis-regulatory elements responsive to light, abscisic acid, auxin, gibberellins, methyl jasmonate, and salicylic acid were identified. Stress-responsive elements and tissue-specific expressed elements were also found. Majority of OsAP genes were found to be expressed in diverse tissues and organs. Some of the OsAP genes were observed to be induced by brassinosteroids, jasmonic acid, and salicylic acid. Further, some OsAP genes can be induced by Xanthomonas oryzae pv. oryzae (Xoo), the cause of rice bacterial leaf blight. Among them, OsAP21 was strongly activated by the pathogen, suggesting its potential function in response to the bacterial agent. The results shed light in the potential functions of OsAP genes in rice disease resistance to Xoo.

Pathogen-induced methylglyoxal negatively regulates rice bacterial blight resistance by inhibiting OsCDR1 protease activity

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight (BB), a globally devastating disease of rice (Oryza sativa) that is responsible for significant crop loss. Sugars and sugar metabolites are important for pathogen infection, providing energy and regulating events associated with defense responses; however, the mechanisms by which they regulate such events in BB are unclear. As an inevitable sugar metabolite, methylglyoxal (MG) is involved in plant growth and responses to various abiotic stresses, but the underlying mechanisms remain enigmatic. Whether and how MG functions in plant biotic stress responses is almost completely unknown. Here, we report that the Xoo strain PXO99 induces OsWRKY62.1 to repress transcription of OsGLY II genes by directly binding to their promoters, resulting in overaccumulation of MG. MG negatively regulates rice resistance against PXO99: osglyII2 mutants with higher MG levels are more susceptible to the pathogen, whereas OsGLYII2-overexpressing plants with lower MG content show greater resistance than the wild type. Overexpression of OsGLYII2 to prevent excessive MG accumulation confers broad-spectrum resistance against the biotrophic bacterial pathogens Xoo and Xanthomonas oryzae pv. oryzicola and the necrotrophic fungal pathogen Rhizoctonia solani, which causes rice sheath blight. Further evidence shows that MG reduces rice resistance against PXO99 through CONSTITUTIVE DISEASE RESISTANCE 1 (OsCDR1). MG modifies the Arg97 residue of OsCDR1 to inhibit its aspartic protease activity, which is essential for OsCDR1-enhanced immunity. Taken together, these findings illustrate how Xoo promotes infection by hijacking a sugar metabolite in the host plant.

Anticandidal Effect of New Imidazole Derivatives Over Aspartic Protease Inhibition.

Candidiasis is one of the most serious microbial infections in the world. One of the main virulence factors for Candida albicans is the crucial secretion of aspartic proteases (Saps). Saps are hydrolytic enzymes that play a major role in many fungal pathophysiological processes as well as in many levels of the associations between the fungus and its host. In this work, we report on the synthesis, characterization, and anti-candida agent evaluation of a family of 13 imidazolidine-based aspartate protease inhibitors. In vitro and in silico enzyme inhibition studies have confirmed these compounds' ability to inhibit fungal aspartate protease. Based on the molecular mechanistic value scores from molecular docking and MD simulations, we selected the top compounds 5b (binding energy -13.90 kcal/mol) and 5m (binding energy -12.94 kcal/mol) from among 5a-l based on the molecular mechanistic value scores from molecular docking and MD simulations for use in in vitro validations. In the results, imidazolidine derivatives showed strong aspartic protease inhibition activity. In conclusion, compounds 5b and 5m were found as potent anti-candida agents and screened for further pre-clinical and clinical validations.