The aim of this study was to prepare tandem multimeric proteins of BmSPI38, a silkworm protease inhibitor, with better structural homogeneity, higher activity and stronger antifungal ability by protein engineering. The tandem multimeric proteins of BmSPI38 were prepared by prokaryotic expression technology. The effects of tandem multimerization on the structural homogeneity, inhibitory activity and antifungal ability of BmSPI38 were explored by in-gel activity staining of protease inhibitor, protease inhibition assays and fungal growth inhibition experiments. Activity staining showed that the tandem expression based on the peptide flexible linker greatly improved the structural homogeneity of BmSPI38 protein. Protease inhibition experiments showed that the tandem trimerization and tetramerization based on the linker improved the inhibitory ability of BmSPI38 to microbial proteases. Conidial germination assays showed that His₆-SPI38L-tetramer had stronger inhibition on conidial germination of Beauveria bassiana than that of His₆-SPI38-monomer. Fungal growth inhibition assay showed that the inhibitory ability of BmSPI38 against Saccharomyces cerevisiae and Candida albicans could be enhanced by tandem multimerization. The present study successfully achieved the heterologous active expression of the silkworm protease inhibitor BmSPI38 in Escherichia coli, and confirmed that the structural homogeneity and antifungal ability of BmSPI38 could be enhanced by tandem multimerization. This study provides important theoretical basis and new strategies for cultivating antifungal transgenic silkworm. Moreover, it may promote the exogenous production of BmSPI38 and its application in the medical field.
Animals ; Antifungal Agents/pharmacology* ; Escherichia coli/metabolism* ; Proteins/metabolism* ; Protease Inhibitors/chemistry* ; Bombyx/chemistry* ; Saccharomyces cerevisiae/metabolism* ; Peptide Hydrolases

The purpose of this study was to investigate the effect of aqueous extract of Corni Fructus on β-amyloid protein 25-35(Aβ_(25-35))-induced brain injury and neuroinflammation in Alzheimer's disease(AD) mice to provide an experimental basis for the treatment of AD by aqueous extract of Corni Fructus. Sixty C57BL/6J male mice were randomly divided into a sham group, a model group, a positive control group(huperizine A, 0.2 mg·kg~(-1)), a low-dose aqueous extract of Corni Fructus group(1.3 g·kg~(-1)), a medium-dose aqueous extract of Corni Fructus group(2.6 g·kg~(-1)), and a high-dose aqueous extract of Corni Fructus group(5.2 g·kg~(-1)). The AD model was induced by lateral ventricular injection of Aβ_(25-35) in mice except for those in the sham group, and AD model mice were treated with corresponding drugs by gavage for 24 days. The behavioral test was performed one week before animal dissection. Hematoxylin-eosin(HE) staining was performed to observe the morphology of neurons in the hippocampal region. Flow cytometry was used to detect the apoptosis level of primary hippocampal cells in mice. ELISA kits were used to detect the levels of β-amyloid protein 1-42(Aβ_(1-42)) and phosphorylated microtubule-associated protein Tau(p-Tau) in mouse brain tissues. Immunofluorescence and Western blot were used to detect the expression of related proteins in mouse brain tissues. MTT assay was used to detect the effect of compounds in aqueous extract of Corni Fructus on Aβ_(25-35)-induced N9 cell injury. Molecular docking was employed to analyze the interactions of caffeic acid, trans-p-hydroxy cinnamic acid, isolariciresinol-9'-O-β-D-glucopyranoside, esculetin, and(+)-lyoniresinol with β-amyloid precursor protein(APP), interleukin-6(IL-6), and tumor necrosis factor-α(TNF-α). Aqueous extract of Corni Fructus could improve the learning and memory abilities of Aβ_(25-35)-induced mice by increasing the duration of the autonomous activity, the rate of autonomous alternation, the preference coefficient, and the discrimination coefficient, and reduce Aβ_(25-35)-induced brain injury and neuroinflammation in mice by increasing the expression levels of interleukin-10(IL-10) and B-cell lymphoma-2(Bcl-2) in brain tissues, decreasing the expression levels of Aβ_(1-42), p-Tau, IL-6, TNF-α, cysteine aspartate-specific protease 3(caspase-3), cysteine aspartate-specific protease 9(caspase-9), and Bcl-2-associated X protein(Bax), and decreasing the number of activated glial cells in brain tissues. The results of cell experiments showed that esculetin and(+)-lyoniresinol could improve Aβ_(25-35)-induced N9 cell injury. Molecular docking results showed that caffeic acid, trans-p-hydroxy cinnamic acid, isolariciresinol-9'-O-β-D-glucopyranoside, esculetin, and(+)-lyoniresinol had good binding affinity with APP and weak binding affinity with IL-6 and TNF-α. Aqueous extract of Corni Fructus could ameliorate cognitive dysfunction and brain damage in Aβ_(25-35)-induced mice by reducing the number of apoptotic cells and activated glial cells in the brain and decreasing the expression level of inflammatory factors. Caffeic acid, trans-p-hydroxy cinnamic acid, isolariciresinol-9'-O-β-D-glucopyranoside, esculetin, and(+)-lyoniresinol may be the material basis for the anti-AD effect of aqueous extract of Corni Fructus.
Mice ; Male ; Animals ; Alzheimer Disease/drug therapy* ; Amyloid beta-Peptides/metabolism* ; Cornus/metabolism* ; Neuroinflammatory Diseases ; Tumor Necrosis Factor-alpha/metabolism* ; Interleukin-6 ; Aspartic Acid ; Cysteine/therapeutic use* ; Molecular Docking Simulation ; Mice, Inbred C57BL ; Brain Injuries ; Peptide Hydrolases ; Disease Models, Animal ; Mice, Transgenic

Acute respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had caused a global pandemic since 2019, and posed a serious threat to global health security. Traditional Chinese medicine (TCM) has played an indispensable role in the battle against the epidemic. Many components originated from TCMs were found to inhibit the production of SARS-CoV-2 3C-like protease (3CLpro) and papain-like protease (PLpro), which are two promising therapeutic targets to inhibit SARS-CoV-2. This study describes a systematic investigation of the roots and rhizomes of Sophora tonkinensis, which results in the characterization of 12 new flavonoids, including seven prenylated flavanones (1-7), one prenylated flavonol (8), two prenylated chalcones (9-10), one isoflavanone (11), and one isoflavan dimer (12), together with 43 known compounds (13-55). Their structures including the absolute configurations were elucidated by comprehensive analysis of MS, 1D and 2D NMR data, and time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculations. Compounds 12 and 51 exhibited inhibitory effects against SARS-CoV-2 3CLpro with IC₅₀ values of 34.89 and 19.88 μmol·L^-1, repectively while compounds 9, 43 and 47 exhibited inhibitory effects against PLpro with IC₅₀ values of 32.67, 79.38, and 16.74 μmol·L^-1, respectively.
Flavonoids/chemistry* ; SARS-CoV-2 ; Rhizome ; COVID-19 ; Peptide Hydrolases ; Antiviral Agents/chemistry*

OBJECTIVE: Jingfang Granules have been recommended for the prevention and treatment of corona virus disease 2019 (COVID-19). Through chemical analysis and bioactivity evaluation, this study aims to elucidate the potential effective components of Jingfang Granules. METHODS: The inhibitory acti-vities of Jingfang Granules extract against 3-chymotrypsin-like protease (3CL^pro), papain like protease (PL^pro), spike protein receptor-binding domain (S-RBD) and human cyclooxygenase-2 (COX-2) were evaluated using enzyme assay. The antitussive effects were evaluated using the classical ammonia-induced cough model. The chemical constituents of Jingfang Granules were qualitatively and quantitatively analyzed by liquid chromatography-mass spectrometry (LC/MS). The 3CL^pro and PL^pro inhibitory activities of the major compounds were determined by enzyme assay, molecular docking, and site-directed mutagenesis. RESULTS: Jingfang Granules exhibited 3CL^pro and PL^pro inhibitory activities, as well as COX-2 inhibitory and antitussive activities. By investigating the MS/MS behaviors of reference standards, a total of fifty-six compounds were characterized in Jingfang Granules. Sixteen of them were unambiguously identified by comparing with reference standards. The contents of the 16 major compounds were also determined, and their total contents were 2 498.8 μg/g. Naringin, nodakenin and neohesperidin were three dominating compounds in Jingfang Granules, and their contents were 688.8, 596.4 and 578.7 μg/g, respectively. In addition, neohesperidin and naringin exhibited PL^pro inhibitory activities, and the inhibition rates at 8 μmol/L were 53.5% and 46.1%, respectively. Prim-O-glucosylcimifugin showed significant inhibitory activities against 3CL^pro and PL^pro, and the inhibitory rates at 8 μmol/L were 76.8% and 78.2%, respectively. Molecular docking indicated that hydrogen bonds could be formed between prim-O-glucosylcimifugin and amino acid residues H163, E166, Q192, T190 of 3CL^pro (binding energy, -7.7 kcal/mol) and K157, D164, R166, E167, T301 of PL^pro(-7.3 kcal/mol), respectively. Site-directed mutagenesis indicated amino acid residue K157 was a key active site for the interaction between prim-O-glucosylcimifugin and PL^pro. CONCLUSION Prim-O-glucosylcimifugin, neohesperidin, and naringin as the major compounds from Jingfang Granules could inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus proteases 3CL^pro and PL^pro. The results are valuable for rational clinical use of Jingfang Granules.
Amino Acids ; Ammonia ; Antitussive Agents ; COVID-19 ; Chymases ; Coronavirus 3C Proteases ; Cyclooxygenase 2 ; Cyclooxygenase 2 Inhibitors ; Cysteine Endopeptidases/metabolism* ; Humans ; Molecular Docking Simulation ; Papain ; Peptide Hydrolases ; SARS-CoV-2 ; Spike Glycoprotein, Coronavirus ; Tandem Mass Spectrometry

OBJECTIVE: Aeromonas has recently been recognized as an emerging human pathogen. Aeromonas-associated diarrhea is a phenomenon occurring worldwide. This study was designed to determine the prevalence, genetic diversity, antibiotic resistance, and pathogenicity of Aeromonas strains isolated from food products in Shanghai. METHODS: Aeromonas isolates ( n = 79) collected from food samples were analyzed using concatenated gyrB- cpn60 sequencing. The antibiotic resistance of these isolates was determined using antimicrobial susceptibility testing. Pathogenicity was assessed using β-hemolytic, extracellular protease, virulence gene detection, C. elegans liquid toxicity (LT), and cytotoxicity assays. RESULTS: Eight different species were identified among the 79 isolates. The most prevalent Aeromonas species were A. veronii [62 (78.5%)], A. caviae [6 (7.6%)], A. dhakensis [3 (3.8%)], and A. salmonicida [3 (3.8%)]. The Aeromonas isolates were divided into 73 sequence types (STs), of which 65 were novel. The isolates were hemolytic (45.6%) and protease-positive (81.0%). The most prevalent virulence genes were act (73.4%), fla (69.6%), aexT (36.7%), and ascV (30.4%). The results of C. elegans LT and cytotoxicity assays revealed that A. dhakensis and A. hydrophila were more virulent than A. veronii, A. caviae, and A. bivalvium. Antibiotic resistance genes [ tetE, blaTEM, tetA, qnrS, aac(6)-Ib, mcr -1, and mcr-3] were detected in the isolates. The multidrug-resistance rate of the Aeromonas isolates was 11.4%, and 93.7% of the Aeromonas isolates were resistant to cefazolin. CONCLUSION The taxonomy, antibiotic resistance, and pathogenicity of different Aeromonas species varied. The Aeromonas isolates A. dhakensis and A. hydrophila were highly pathogenic, indicating that food-derived Aeromonas isolates are potential risks for public health and food safety. The monitoring of food quality and safety will result in better prevention and treatment strategies to control diarrhea illnesses in China.
Aeromonas/genetics* ; Animals ; Anti-Bacterial Agents/pharmacology* ; Caenorhabditis elegans ; Cefazolin ; China/epidemiology* ; Diarrhea ; Drug Resistance, Multiple, Bacterial/genetics* ; Genetic Variation ; Humans ; Peptide Hydrolases/genetics* ; Virulence/genetics*

Genome sequences of 4 644 representative strains from human gut microbiota were analyzed to mine gene clusters for biosynthesis of novel secondary metabolites, as well as genes encoding antibiotic resistance and virulence factors. AntiSMASH analysis showed that more than 60% of the representative strains encoded at least one secondary metabolite gene cluster, and 8 potential novel secondary metabolite gene clusters were identified from 8 unculturable bacteria. The secondary metabolite gene clusters in human intestine are mainly composed of nonribosomal peptide synthetase (NRPS), bacteriocin, arylpolyene, terpene, betalactone and NRPS like gene clusters distributed in Clostridia, Bacilli, Gammaproteobacteria, Bacteroidia, Actinobacteria and Negativicutes. PathoFact analysis showed that genes encoding antibiotic resistance and virulence factors are widely distributed in representative strains, but the frequency encoded by potential pathogens is significantly higher than that of non-potential pathogens. The frequency of genes encoding secretory toxins such as outer membrane protein, PapC N-terminal domain, PapC C-terminal domain, peptidase M16 inactive domain, and non-secretory toxins such as nitroreductase family, AcrB/AcrD/AcrF family, PLD-like domain, Cupin domain, putative hemolysin, S24-like peptidase, phosphotransferase enzyme family, endonuclease/ exonuclease/ phosphatase family, glyoxalase/ bleomycin resistance was high in potential pathogens. This study may facilitate mining new microbial natural products from the intestinal microbiome, understanding the colonization and infection mechanism of intestinal microorganisms, and providing targeted prevention and treatment of intestinal microbial related diseases.
Humans ; Virulence ; Multigene Family ; Bacteria ; Drug Resistance, Microbial ; Virulence Factors ; Peptide Hydrolases

Proteases are widely found in organisms participating in the decomposition of proteins to maintain the organisms' normal life activities. Protease inhibitors regulate the activities of target proteases by binding to their active sites, thereby affecting protein metabolism. The key amino acid mutations in proteases and protease inhibitors can affect their physiological functions, stability, catalytic activity, and inhibition specificity. More active, stable, specific, environmentally friendly and cheap proteases and protease inhibitors might be obtained by excavating various natural mutants of proteases and protease inhibitors, analyzing their key active sites by using protein engineering methods. Here, we review the studies on proteases' key active sites and protease inhibitors to deepen the understanding of the active mechanism of proteases and their inhibitors.
Binding Sites ; Catalytic Domain ; Endopeptidases ; Peptide Hydrolases/genetics* ; Protease Inhibitors ; Proteins

The main protease (Mpro) of SARS-CoV-2 is a highly conserved and mutation-resistant coronaviral enzyme, which plays a pivotal role in viral replication, making it an ideal target for the development of novel broad-spectrum anti-coronaviral drugs. In this study, a codon-optimized Mpro gene was cloned into pET-21a and pET-28a expression vectors. The recombinant plasmids were transformed into E. coli Rosetta(DE3) competent cells and the expression conditions were optimized. The highly expressed recombinant proteins, Mpro and Mpro-28, were purified by HisTrapTM chelating column and its proteolytic activity was determined by a fluorescence resonance energy transfer (FRET) assay. The FRET assay showed that Mpro exhibits a desirable proteolytic activity (25 000 U/mg), with Km and kcat values of 11.68 μmol/L and 0.037/s, respectively. The specific activity of Mpro is 25 times that of Mpro-28, a fusion protein carrying a polyhistidine tag at the N and C termini, indicating additional residues at the N terminus of Mpro, but not at the C terminus, are detrimental to its proteolytic activity. The preparation of active SARS-CoV-2 Mpro through codon-optimization strategy might facilitate the development of the rapid screening assays for the discovery of broad-spectrum anti-coronaviral drugs targeting Mpro.
COVID-19 ; Codon/genetics* ; Cysteine Endopeptidases/genetics* ; Escherichia coli/genetics* ; Humans ; Peptide Hydrolases ; SARS-CoV-2 ; Viral Nonstructural Proteins/genetics*

The general secretory (Sec) pathway represents a common mechanism by which bacteria secrete proteins, including virulence factors, into the extracytoplasmic milieu. However, there is little information about this system, as well as its associated secretory proteins, in relation to the fire blight pathogen Erwinia amylovora. In this study, data mining revealed that E. amylovora harbors all of the essential components of the Sec system. Based on this information, we identified putative Sec-dependent secretory proteases in E. amylovora on a genome-wide scale. Using the programs SignalP, LipoP, and Phobius, a total of 15 putative proteases were predicted to contain the N-terminal signal peptides (SPs) that might link them to the Sec-dependent pathway. The activities of the predicted SPs were further validated using an Escherichia coli-based alkaline phosphatase (PhoA) gene fusion system that confirmed their extracytoplasmic property. Transcriptional analyses showed that the expression of 11 of the 15 extracytoplasmic protease genes increased significantly when E. amylovora was used to inoculate immature pears, suggesting their potential roles in plant infection. The results of this study support the suggestion that E. amylovora might employ the Sec system to secrete a suite of proteases to enable successful infection of plants, and shed new light on the interaction of E. amylovora with host plants.
Erwinia amylovora/metabolism* ; Escherichia coli/genetics* ; Peptide Hydrolases/genetics* ; Plant Diseases/microbiology* ; Pyrus/microbiology*

Adaptor Proteins, Signal Transducing ; Humans ; Lymphoma, Large B-Cell, Diffuse ; Peptide Hydrolases ; Prognosis ; Ubiquitin-Protein Ligases