Inhibitors of Rickettsia prowazekii methionine aminopeptidase 1 identified from the Pandemic Response Box.

Methionine aminopeptidase (MetAp) enzymes catalyze the post-translational removal of the initiator methionine residue in newly synthesized proteins, a process that is often essential in the maturation of proteins. Consequently, these enzymes serve as important targets for drug development. Rickettsia prowazekii (Rp) is an obligate coccobacillus and the causative agent of the louse-borne epidemic typhus and despite adequate treatment causes a latent infection. This research aimed to identify potential anti-rickettsial agents by screening 400 compounds from the MMV Pandemic Response Box against RpMetAp1. Overall, 19 compounds were identified that possessed IC50 values from 10 µM to 340 nM. The most potent inhibitor was MMV 1580488 (17), which was observed to have an IC50 of 340 nM. The selected hits serve as chemical leads that can be used for the development of potent inhibitors of the RpMetAp1 enzyme.

The Secreted Aminopeptidase of Pseudomonas aeruginosa (PaAP).

Pseudomonas aeruginosa is an opportunistic pathogen that causes severe infections in compromised hosts. P. aeruginosa infections are difficult to treat because of the inherent ability of the bacteria to develop antibiotic resistance, secrete a variety of virulence factors, and form biofilms. The secreted aminopeptidase (PaAP) is an emerging virulence factor, key in providing essential low molecular weight nutrients and a cardinal modulator of biofilm development. PaAP is therefore a new potential target for therapy of P. aeruginosa infections. The present review summarizes the current knowledge of PaAP, with special emphasis on its biochemical and enzymatic properties, activation mechanism, biological roles, regulation, and structure. Recently developed specific inhibitors and their potential as adjuncts in the treatment of P. aeruginosa infections are also described.

The effect of rs2910686 on ERAP2 expression in IBD and epithelial inflammatory response.

BACKGROUND: ERAP2 is an aminopeptidase involved in antigen processing and presentation, and harbor genetic variants linked to several inflammatory diseases such as Inflammatory Bowel Disease (IBD). The lack of an ERAP2 gene homologue in mice has hampered functional studies, and most human studies have focused on cells of hematopoietic origin. Using an IBD biobank as vantage point, this study explores how genetic variation in ERAP2 affects gene expression in human-derived epithelial organoids upon proinflammatory stimulation. METHODS: An IBD patient cohort was genotyped with regards to two single nucleotide polymorphisms (SNP) (rs2910686/rs2248374) associated with ERAP2 expression levels, and we examined the correlation between colon gene expression and genotype, specifically aiming to establish a relationship with ERAP2 expression proficiency. Human-derived colon organoids (colonoids) with known ERAP2 genotype were established and used to explore differences in whole genome gene expression between ERAP2-deficient (n = 4) and -proficient (n = 4) donors upon pro-inflammatory encounter. RESULTS: When taking rs2910686 genotype into account, ERAP2 gene expression is upregulated in the inflamed colon of IBD patients. Colonoids upregulate ERAP2 upon IFNÉ£ stimulation, and ERAP2 expression proficiency is dependent on rs2910686 genotype. Colonoid genotyping confirms that mechanisms independent of the frequently studied SNP rs2248374 can cause ERAP2-deficiency. A total of 586 genes involved in various molecular mechanisms are differentially expressed between ERAP2 proficient- and deficient colonoids upon proinflammatory stimulation, including genes encoding proteins with the following molecular function: catalytic activity (AOC1, CPE, ANPEP and MEP1A), regulator activity (TNFSF9, MDK, GDF15, ILR6A, LGALS3 and FLNA), transmembrane transporter activity (SLC40A1 and SLC5A1), and extracellular matrix structural constituents (FGL2, HMCN2, and MUC17). CONCLUSIONS: ERAP2 is upregulated in the inflamed IBD colon mucosa, and expression proficiency is highly correlated with genotype of rs2910686. While the SNP rs2248374 is commonly used to determine ERAP2 expressional proficiency, our data confirms that mechanisms independent of this SNP can lead to ERAP2 deficiency. Our data demonstrates that epithelial ERAP2 presence affects the inflammatory response in colonoids, suggesting a pleiotropic role of ERAP2 beyond MHC class I antigen processing.

ERAP Inhibitors in Autoimmunity and Immuno-Oncology: Medicinal Chemistry Insights.

Endoplasmic reticulum aminopeptidases ERAP1 and 2 are intracellular aminopeptidases that trim antigenic precursors and generate antigens presented by major histocompatibility complex class I (MHC-I) molecules. They thus modulate the antigenic repertoire and drive the adaptive immune response. ERAPs are considered as emerging targets for precision immuno-oncology or for the treatment of autoimmune diseases, in particular MHC-I-opathies. This perspective covers the structural and biological characterization of ERAP, their relevance to these diseases and the ongoing research on small-molecule inhibitors. We describe the chemical and pharmacological space explored by medicinal chemists to exploit the potential of these targets given their localization, biological functions, and family depth. Specific emphasis is put on the binding mode, potency, selectivity, and physchem properties of inhibitors featuring diverse scaffolds. The discussion provides valuable insights for the future development of ERAP inhibitors and analysis of persisting challenges for the translation for clinical applications.

Carnosic Acid: A Novel Selective Inhibitor of ERAP1 by Direct Binding and Its Modulation of Antigen Processing and Presentation.

ERAP1 is an emerging target for a large subclass of severe autoimmune diseases known as "MHC-I-opathy", together with tumor immunity. Nevertheless, effective inhibitors targeting ERAP1 remain a challenge. In this study, a novel food-derived natural product ERAP1-targeting inhibitor, carnosic acid, was identified, and to our knowledge, it is one of the best active compounds among the highly selective inhibitors targeting the orthosteric site of ERAP1. The results reveal that carnosic acid could bind strongly, like a key to the ERAP1 active site in the biased S1' pocket, which is different from the binding mode of the existing orthosteric site inhibitors. HLA-B27-mediated cell modeling validated that carnosic acid has the activity to reverse the AS-associated cellular phenotype brought on by ERAP1 through inhibition. Our findings provide insights into the design of potent inhibitors against the ERAP1 orthosteric site and the discovery of a key direct target of carnosic acid.

Chemoproteomics validates selective targeting of Plasmodium M1 alanyl aminopeptidase as an antimalarial strategy.

New antimalarial drug candidates that act via novel mechanisms are urgently needed to combat malaria drug resistance. Here, we describe the multi-omic chemical validation of Plasmodium M1 alanyl metalloaminopeptidase as an attractive drug target using the selective inhibitor, MIPS2673. MIPS2673 demonstrated potent inhibition of recombinant Plasmodium falciparum (PfA-M1) and Plasmodium vivax (PvA-M1) M1 metalloaminopeptidases, with selectivity over other Plasmodium and human aminopeptidases, and displayed excellent in vitro antimalarial activity with no significant host cytotoxicity. Orthogonal label-free chemoproteomic methods based on thermal stability and limited proteolysis of whole parasite lysates revealed that MIPS2673 solely targets PfA-M1 in parasites, with limited proteolysis also enabling estimation of the binding site on PfA-M1 to within ~5 Å of that determined by X-ray crystallography. Finally, functional investigation by untargeted metabolomics demonstrated that MIPS2673 inhibits the key role of PfA-M1 in haemoglobin digestion. Combined, our unbiased multi-omic target deconvolution methods confirmed the on-target activity of MIPS2673, and validated selective inhibition of M1 alanyl metalloaminopeptidase as a promising antimalarial strategy.

Substrate Characterization for Hydrolysis of Multiple Types of Aromatic Esters by Promiscuous Aminopeptidases.

Synthetic aromatic esters, widely employed in agriculture, food, and chemical industries, have become emerging environmental pollutants due to their strong hydrophobicity and poor bioavailability. This study attempted to address this issue by extracellularly expressing the promiscuous aminopeptidase (Aps) from Pseudomonas aeruginosa GF31 in B. subtilis, achieving an impressive enzyme activity of 13.7 U/mg. Notably, we have demonstrated, for the first time, the Aps-mediated degradation of diverse aromatic esters, including but not limited to pyrethroids, phthalates, and parabens. A biochemical characterization of Aps reveals its esterase properties and a broader spectrum of substrate profiles. The degradation rates of p-nitrobenzene esters (p-NB) with different side chain structures vary under the action of Aps, showing a preference for substrates with relatively longer alkyl side chains. The structure-dependent degradability aligns well with the binding energies between Aps and p-NB. Molecular docking and enzyme-substrate interaction elucidate that hydrogen bonding, hydrophobic interactions, and π-π stacking collectively stabilize the enzyme-substrate conformation, promoting substrate hydrolysis. These findings provide new insights into the enzymatic degradation of aromatic ester pollutants, laying a foundation for the further development and modification of promiscuous enzymes.

Modulation of endogenous opioid signaling by inhibitors of puromycin-sensitive aminopeptidase.

The endogenous opioid system regulates pain through local release of neuropeptides and modulation of their action on opioid receptors. However, the effect of opioid peptides, the enkephalins, is short-lived due to their rapid hydrolysis by enkephalin-degrading enzymes. In turn, an innovative approach to the management of pain would be to increase the local concentration and prolong the stability of enkephalins by preventing their inactivation by neural enkephalinases such as puromycin-sensitive aminopeptidase (PSA). Our previous structure-activity relationship studies offered the S-diphenylmethyl cysteinyl derivative of puromycin (20) as a nanomolar inhibitor of PSA. This chemical class, however, suffered from undesirable metabolism to nephrotoxic puromycin aminonucleoside (PAN). To prevent such toxicity, we designed and synthesized 5'-chloro substituted derivatives. The compounds retained the PSA inhibitory potency of the corresponding 5'-hydroxy analogs and had improved selectivity toward PSA. In vivo treatment with the lead compound 19 caused significantly reduced pain response in antinociception assays, alone and in combination with Met-enkephalin. The analgesic effect was reversed by the opioid antagonist naloxone, suggesting the involvement of opioid receptors. Further, PSA inhibition by compound 19 in brain slices caused local increase in endogenous enkephalin levels, corroborating our rationale. Pharmacokinetic assessment of compound 19 showed desirable plasma stability and identified the cysteinyl sulfur as the principal site of metabolic liability. We gained additional insight into inhibitor-PSA interactions by molecular modeling, which underscored the importance of bulky aromatic amino acid in puromycin scaffold. The results of this study strongly support our rationale for the development of PSA inhibitors for effective pain management.

ERAMER: A novel in silico tool for prediction of ERAP1 enzyme trimming.

MHC class I pathway consists of four main steps: proteasomal cleavage in the cytosol in which precursor proteins are cleaved into smaller peptides, which are then transported into the endoplasmic reticulum by the transporter associated with antigen processing, TAP, for further processing (trimming) from the N-terminal region by an ER resident aminopeptidases 1 (ERAP1) enzyme, to generate optimal peptides (8-10 amino acids in length) to produce a stable MHCI-peptide complex, that get transited via the Golgi apparatus to the cell surface for presentation to the cellular immune system. Several studies reported specificities related to the ERAP1 trimming process, yet there is no in silico tool for the prediction of the trimming process of the ERAP1 enzyme. In this paper, we provide and implement a prediction model for the trimming process of the ERAP1 enzyme.

On-target, dual aminopeptidase inhibition provides cross-species antimalarial activity.

To combat the global burden of malaria, development of new drugs to replace or complement current therapies is urgently required. Here, we show that the compound MMV1557817 is a selective, nanomolar inhibitor of both Plasmodium falciparum and Plasmodium vivax aminopeptidases M1 and M17, leading to inhibition of end-stage hemoglobin digestion in asexual parasites. MMV1557817 can kill sexual-stage P. falciparum, is active against murine malaria, and does not show any shift in activity against a panel of parasites resistant to other antimalarials. MMV1557817-resistant P. falciparum exhibited a slow growth rate that was quickly outcompeted by wild-type parasites and were sensitized to the current clinical drug, artemisinin. Overall, these results confirm MMV1557817 as a lead compound for further drug development and highlights the potential of dual inhibition of M1 and M17 as an effective multi-species drug-targeting strategy.IMPORTANCEEach year, malaria infects approximately 240 million people and causes over 600,000 deaths, mostly in children under 5 years of age. For the past decade, artemisinin-based combination therapies have been recommended by the World Health Organization as the standard malaria treatment worldwide. Their widespread use has led to the development of artemisinin resistance in the form of delayed parasite clearance, alongside the rise of partner drug resistance. There is an urgent need to develop and deploy new antimalarial agents with novel targets and mechanisms of action. Here, we report a new and potent antimalarial compound, known as MMV1557817, and show that it targets multiple stages of the malaria parasite lifecycle, is active in a preliminary mouse malaria model, and has a novel mechanism of action. Excitingly, resistance to MMV15578117 appears to be self-limiting, suggesting that development of the compound may provide a new class of antimalarial.

Synthesis and Evaluation of diaryl ether modulators of the leukotriene A4 hydrolase aminopeptidase activity.

Activation of the aminopeptidase (AP) activity of leukotriene A4 hydrolase (LTA4H) presents a potential therapeutic strategy for resolving chronic inflammation. Previously, ARM1 and derivatives were found to activate the AP activity using the alanine-p-nitroanilide (Ala-pNA) as a reporter group in an enzyme kinetics assay. As an extension of this previous work, novel ARM1 derivatives were synthesized using a palladium-catalyzed Ullmann coupling reaction and screened using the same assay. Analogue 5, an aminopyrazole (AMP) analogue of ARM1, was found to be a potent AP activator with an AC50 of 0.12 µM. An X-ray crystal structure of LTA4H in complex with AMP was refined at 2.7 Å. Despite its AP activity with Ala-pNA substrate, AMP did not affect hydrolysis of the previously proposed natural ligand of LTA4H, Pro-Gly-Pro (PGP). This result highlights a discrepancy between the hydrolysis of more conveniently monitored chromogenic synthetic peptides typically employed in assays and endogenous peptides. The epoxide hydrolase (EH) activity of AMP was measured in vivo and the compound significantly reduced leukotriene B4 (LTB4) levels in a murine bacterial pneumonia model. However, AMP did not enhance survival in the murine pneumonia model over a 14-day period. A liver microsome stability assay showed metabolic stability of AMP. The results suggested that accelerated Ala-pNA cleavage is not sufficient for predicting therapeutic potential, even when the full mechanism of activation is known.

Crystal structure of a newly identified M61 family aminopeptidase with broad substrate specificity that is solely responsible for recycling acidic amino acids.

Aminopeptidases with varied substrate specificities are involved in different crucial physiological processes of cellular homeostasis. They also have wide applications in food and pharma industries. Within the bacterial cell, broad specificity aminopeptidases primarily participate in the recycling of amino acids by degrading oligopeptides generated via primary proteolysis mediated by cellular ATP-dependent proteases. However, in bacteria, a truly broad specificity enzyme, which can cleave off acidic, basic, Gly and hydrophobic amino acid residues, is extremely rare. Here, we report structure-function of a putative glycyl aminopeptidase (M61xc) from Xanthomonas campestris pv campestris (Xcc) belonging to the M61 peptidase family. The enzyme exhibits broad specificity and cleaves Ala, Leu, Asp, Glu, Met, Ser, Phe, Tyr, Gly, Arg, and Lys at the N terminus, optimally of peptides with a length of 3-7 amino acids. Further, we report the high-resolution crystal structure of M61xc in the apo form (2.1 Å) and bestatin-bound form (1.95 Å), detailing its catalytic and substrate preference mechanisms. Comparative analysis of enzyme activity in crude cell extracts from both wild-type and m61xc-knockout mutant strains of Xcc has elucidated the unique intracellular role of M61xc. This study suggests that M61xc is the exclusive enzyme in these bacteria that is responsible for liberating Asp/Glu residues from the N-termini of peptides. Also, in view of its broad specificity and peptide degradation ability, it could be considered equivalent to M1 or other oligomeric peptidases from families like M17, M18, M42 or S9, who have an important auxiliary role in post-proteasomal protein degradation in prokaryotes.

Characterization, Semirational Design for pH Robustness, and the Application in Bioactive Peptide Production of a X-Prolyl Dipeptidyl Aminopeptidase from Lactococcus lactis MY-3.

PepXLcMY-3, an X-prolyl dipeptidyl aminopeptidase derived from Lactobacillus lactis MY-3, was screened and recombinantly expressed in Escherichia coli. The enzyme could exhibit about 40% activity within the pH range of 6.0-10. To further improve the pH robustness, site E396 located in the active pocket was discovered through alanine scanning. The mutant E396I displayed both developed activity and kcat/Km. The optimal pH of E396I shifted from 6.0 to 10 compared to WT, with the relative activity within the pH range of 6.0-10 significantly increased. The site K648 was then proposed by semirational design. The activity of mutant E396I/K648D reached 4.03 U/mg. The optimal pH was restored to 6.0, and the pH stability was further improved. E396I/K648D could totally hydrolyze ß-casomorphin 7 within 30 min. The hydrolysate showed 64.5% inhibition on angiotensin I converting enzyme, which was more efficient than those produced by E396I and WT, 23.2 and 44.7%, respectively.

Identification of immunological patterns characterizing immune-related psoriasis reactions in oncological patients in therapy with anti-PD-1 checkpoint inhibitors.

Introduction: Immunotherapy with biologics targeting programmed cell death protein-1 (PD-1) is highly effective in the treatment of various malignancies. Nevertheless, it is frequently responsible for unexpected cutaneous manifestations, including psoriasis-like dermatitis. The pathogenesis of anti-PD-1-induced psoriasis has yet to be clarified, even though it is plausible that some innate and adaptive immunity processes are in common with canonical psoriasis. The genetic predisposition to psoriasis of patients could also be a contributing factor. Here, we investigated the immunological and genetic profiles of two patients with metastatic melanoma and one patient affected by lung cancer, who developed severe psoriasis after receiving anti-PD-1 nivolumab therapy. Methods: The immune patterns of the three patients were compared with those detectable in classical, chronic plaque-type psoriasis or paradoxical psoriasis induced by anti-TNF-α therapy, mostly sustained by adaptive and innate immunity processes, respectively. Therefore, immunohistochemistry and mRNA analyses of innate and adaptive immunity molecules were conducted on skin biopsy of patients. Genetic analysis of polymorphisms predisposing to psoriasis was carried out by NGS technology. Results: We found that anti-PD-1-induced psoriasis showed immunological features similar to chronic psoriasis, characterized by the presence of cellular players of adaptive immunity, with abundant CD3+, CD8+ T cells and CD11c+ dendritic cells infiltrating skin lesions, and producing IL-23, IL-6, TNF-α, IFN-γ and IL-17. On the contrary, a lower number of innate immunity cells (BDCA2+ plasmacytoid dendritic cells, CD15+ neutrophils, CD117+ mast cells) and reduced IFN-α/ß, lymphotoxin (LT)-α/ß, were observed in anti-PD-1-induced psoriasis lesions, as compared with anti-TNF-α-induced paradoxical psoriasis. Importantly, the disintegrin and metalloprotease domain containing thrombospondin type 1 motif-like 5 (ADAMTSL5) psoriasis autoantigen was significantly upregulated in psoriasis lesions of anti-PD-1-treated patients, at levels comparable with chronic plaque-type psoriasis. Finally, NGS analysis revealed that all patients carried several allelic variants in psoriasis susceptibility genes, such as HLA-C, ERAP1 and other genes of the major psoriasis susceptibility PSORS1 locus. Discussion: Our study showed that adaptive immunity predominates over innate immunity in anti-PD-1-induced psoriasis lesions, consistently with the local ADAMTSL5 overexpression. The presence of numerous SNPs in psoriasis susceptibility genes of the three patients also suggested their strong predisposition to the disease.

NPEPPS Is a Druggable Driver of Platinum Resistance.

There is an unmet need to improve the efficacy of platinum-based cancer chemotherapy, which is used in primary and metastatic settings in many cancer types. In bladder cancer, platinum-based chemotherapy leads to better outcomes in a subset of patients when used in the neoadjuvant setting or in combination with immunotherapy for advanced disease. Despite such promising results, extending the benefits of platinum drugs to a greater number of patients is highly desirable. Using the multiomic assessment of cisplatin-responsive and -resistant human bladder cancer cell lines and whole-genome CRISPR screens, we identified puromycin-sensitive aminopeptidase (NPEPPS) as a driver of cisplatin resistance. NPEPPS depletion sensitized resistant bladder cancer cells to cisplatin in vitro and in vivo. Conversely, overexpression of NPEPPS in sensitive cells increased cisplatin resistance. NPEPPS affected treatment response by regulating intracellular cisplatin concentrations. Patient-derived organoids (PDO) generated from bladder cancer samples before and after cisplatin-based treatment, and from patients who did not receive cisplatin, were evaluated for sensitivity to cisplatin, which was concordant with clinical response. In the PDOs, depletion or pharmacologic inhibition of NPEPPS increased cisplatin sensitivity, while NPEPPS overexpression conferred resistance. Our data present NPEPPS as a druggable driver of cisplatin resistance by regulating intracellular cisplatin concentrations. SIGNIFICANCE: Targeting NPEPPS, which induces cisplatin resistance by controlling intracellular drug concentrations, is a potential strategy to improve patient responses to platinum-based therapies and lower treatment-associated toxicities.

Recent Advances of Aminopeptidases-Responsive Small-Molecular Probes for Bioimaging.

Aminopeptidases, enzymes with critical roles in human body, are emerging as vital biomarkers for metabolic processes and diseases. Aberrant aminopeptidase levels are often associated with diseases, particularly cancer. Small-molecule probes, such as fluorescent, fluorescent/photoacoustics, bioluminescent, and chemiluminescent probes, are essential tools in the study of aminopeptidases-related diseases. The fluorescent probes provide real-time insights into protein activities, offering high sensitivity in specific locations, and precise spatiotemporal results. Additionally, photoacoustic probes offer signals that are able to penetrate deeper tissues. Bioluminescent and chemiluminescent probes can enhance in vivo imaging abilities by reducing the background. This comprehensive review is focused on small-molecule probes that respond to four key aminopeptidases: aminopeptidase N, leucine aminopeptidase, Pyroglutamate aminopeptidase 1, and Prolyl Aminopeptidase, and their utilization in imaging tumors and afflicted regions. In this review, the design strategy of small-molecule probes, the variety of designs from previous studies, and the opportunities of future bioimaging applications are discussed, serving as a roadmap for future research, sparking innovations in aminopeptidase-responsive probe development, and enhancing our understanding of these enzymes in disease diagnostics and treatment.

Pharmacological Characterization of SDX-7320/Evexomostat: A Novel Methionine Aminopeptidase Type 2 Inhibitor with Anti-tumor and Anti-metastatic Activity.

Methionine aminopeptidase type 2 (METAP2) is a ubiquitous, evolutionarily conserved metalloprotease fundamental to protein biosynthesis which catalyzes removal of the N-terminal methionine residue from nascent polypeptides. METAP2 is an attractive target for cancer therapeutics based upon its over-expression in multiple human cancers, the importance of METAP2-specific substrates whose biological activity may be altered following METAP2 inhibition, and additionally, that METAP2 was identified as the target for the anti-angiogenic natural product, fumagillin. Irreversible inhibition of METAP2 using fumagillin analogues has established the anti-angiogenic and anti-tumor characteristics of these derivatives; however, their full clinical potential has not been realized due to a combination of poor drug-like properties and dose-limiting central nervous system (CNS) toxicity. This report describes the physicochemical and pharmacological characterization of SDX-7320 (evexomostat), a polymer-drug conjugate of the novel METAP2 inhibitor (METAP2i) SDX-7539. In vitro binding, enzyme, and cell-based assays demonstrated that SDX-7539 is a potent and selective METAP2 inhibitor. In utilizing a high molecular weight, water-soluble polymer to conjugate the novel fumagillol-derived, cathepsin-released, METAP2i SDX-7539, limitations observed with prior generation, small molecule fumagillol derivatives were ameliorated including reduced CNS exposure of the METAP2i, and prolonged half-life enabling convenient administration. Multiple xenograft and syngeneic cancer models were utilized to demonstrate the anti-tumor and anti-metastatic profile of SDX-7320. Unlike polymer-drug conjugates in general, reductions in small molecule-equivalent efficacious doses following polymer conjugation were observed. SDX-7320 has completed a phase I clinical safety study in patients with late-stage cancer and is currently being evaluated in multiple phase Ib/II clinical studies in patients with advanced solid tumors.

Preparation of pH-responsive chitosan microspheres containing aminopeptidase and their application in accelerating cheese ripening.

Microencapsulated enzymes have been found to effectively accelerate cheese ripening. However, microencapsulated enzyme release is difficult to control, often resulting in enzyme release during cheese processing and causing texture and flavor defects. This study aims to address this issue by developing aminopeptidase-loaded pH-responsive chitosan microspheres (A-CM) for precise enzyme release during cheese ripening. An aminopeptidase with an isoelectric point (pH 5.4) close to the pH value of cheese ripening was loaded on chitosan microspheres through electrostatic interaction. Turbidity titration measurements revealed that pH 6.5 was optimal for binding aminopeptidase and microspheres, affording the highest loading efficiency of 58.16%. Various characterization techniques, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy confirmed the successful loading of aminopeptidase molecules on the chitosan microspheres. In vitro release experiments conducted during simulated cheese production demonstrated that aminopeptidase release from A-CM was pH responsive. The microspheres retained the enzyme during the coagulation and cheddaring processes (pH 5.5-6.5) and only released it after entering the cheese-ripening stage (pH 5.0-5.5). By loading aminopeptidase on chitosan microspheres, the loss rate of the enzyme in cheese whey was reduced by approximately 79%. Furthermore, compared with cheese without aminopeptidase and cheese with aminopeptidase added directly, the cheeses made with A-CM exhibited the highest proteolysis level and received superior sensory ratings for taste and smell. The content of key aroma substances, such as 2/3-methylbutanal and ethyl butyrate, in cheese with A-CM was more than 15 times higher than the others. This study provides an approach for accelerating cheese ripening through the use of microencapsulated enzymes.

A genetic variant in the immune-related gene ERAP1 affects colorectal cancer prognosis.

BACKGROUND: Findings on the association of genetic factors and colorectal cancer (CRC) survival are limited and inconsistent, and revealing the mechanism underlying their prognostic roles is of great importance. This study aimed to explore the relationship between functional genetic variations and the prognosis of CRC and further reveal the possible mechanism. METHODS: We first systematically performed expression quantitative trait locus (eQTL) analysis using The Cancer Genome Atlas (TCGA) dataset. Then, the Kaplan-Meier analysis was used to filter out the survival-related eQTL target genes of CRC patients in two public datasets (TCGA and GSE39582 dataset from the Gene Expression Omnibus database). The seven most potentially functional eQTL single nucleotide polymorphisms (SNPs) associated with six survival-related eQTL target genes were genotyped in 907 Chinese CRC patients with clinical prognosis data. The regulatory mechanism of the survival-related SNP was further confirmed by functional experiments. RESULTS: The rs71630754 regulating the expression of endoplasmic reticulum aminopeptidase 1 ( ERAP1 ) was significantly associated with the prognosis of CRC (additive model, hazard ratio [HR]: 1.43, 95% confidence interval [CI]: 1.08-1.88, P = 0.012). The results of dual-luciferase reporter assay and electrophoretic mobility shift assay showed that the A allele of the rs71630754 could increase the binding of transcription factor 3 (TCF3) and subsequently reduce the expression of ERAP1 . The results of bioinformatic analysis showed that lower expression of ERAP1 could affect the tumor immune microenvironment and was significantly associated with severe survival outcomes. CONCLUSION: The rs71630754 could influence the prognosis of CRC patients by regulating the expression of the immune-related gene ERAP1 . TRIAL REGISTRATION: No. NCT00454519 ( https://clinicaltrials.gov/ ).

Structure-guided discovery of aminopeptidase ERAP1 variants capable of processing antigens with novel PC anchor specificities.

Endoplasmic reticulum aminopeptidase 1 (ERAP1) belongs to the oxytocinase subfamily of M1 aminopeptidases (M1APs), which are a diverse family of metalloenzymes involved in a wide range of functions and have been implicated in various chronic and infectious diseases of humans. ERAP1 trims antigenic precursors into correct sizes (8-10 residues long) for Major Histocompatibility Complex (MHC) presentation, by a unique molecular ruler mechanism in which it makes concurrent bindings to substrate N- and C-termini. We have previously determined four crystal structures of ERAP1 C-terminal regulatory domain (termed ERAP1_C domain) in complex with peptide carboxyl (PC)-ends that carry various anchor residues, and identified a specificity subsite for recognizing the PC anchor side chain, denoted as the SC subsite to follow the conventional notations: S1 site for P1, S2 site for P2, and so forth. In this study, we report studies on structure-guided mutational and hydrolysis kinetics, and peptide trimming assays to further examine the functional roles of this SC subsite. Most strikingly, a point mutation V737R results in a change of substrate preference from a hydrophobic to a negatively charged PC anchor residue; the latter is presumed to be a poor substrate for WT ERAP1. These studies validate the crystallographic observations that this SC subsite is directly involved in binding and recognition of the substrate PC anchor and presents a potential target to modulate MHC-restricted immunopeptidomes.