PEGylation renders carnosine resistant to hydrolysis by serum carnosinase and increases renal carnosine levels.

Carnosine's protective effect in rodent models of glycoxidative stress have provided a rational for translation of these findings in therapeutic concepts in patient with diabetic kidney disease. In contrast to rodents however, carnosine is rapidly degraded by the carnosinase-1 enzyme. To overcome this hurdle, we sought to protect hydrolysis of carnosine by conjugation to Methoxypolyethylene glycol amine (mPEG-NH2). PEGylated carnosine (PEG-car) was used to study the hydrolysis of carnosine by human serum as well as to compare the pharmacokinetics of PEG-car and L-carnosine in mice after intravenous (IV) injection. While L-carnosine was rapidly hydrolyzed in human serum, PEG-car was highly resistant to hydrolysis. Addition of unconjugated PEG to carnosine or PEG-car did not influence hydrolysis of carnosine in serum. In mice PEG-car and L-carnosine exhibited similar pharmacokinetics in serum but differed in half-life time (t1/2) in kidney, with PEG-car showing a significantly higher t1/2 compared to L-carnosine. Hence, PEGylation of carnosine is an effective approach to prevent carnosine degradations and to achieve higher renal carnosine levels. However, further studies are warranted to test if the protective properties of carnosine are preserved after PEGylation.

Prolidase activity in women with polycystic ovarian syndrome undergoing assisted conception.

Background: Prolidase is a manganese (Mn)-dependent cytosolic exopeptidase that degrades imidodipeptides with C-terminal proline or hydroxyproline. Prolidase recycling from imidodipeptides plays a critical role in collagen resynthesis and extracellular matrix (ECM) remodelling. Following an increase in gonadotropins, ovarian and follicular collagen undergo substantial degradation. Abnormal ovarian ECM composition is associated with polycystic ovary syndrome (PCOS). This study aimed to examine prolidase activity in the serum and follicular fluid (FF) of women undergoing in vitro fertilisation/intracytoplasmic sperm injection (IVF/ICSI) treatment, comparing those with PCOS to those with normal ovarian function.Methods: This prospective study enrolled 50 participants, of whom 44 were included. PCOS diagnosis followed the Rotterdam consensus criteria, with 20 patients constituting the study group. The control group comprised 24 individuals with mild-to-moderate male infertility. Prolidase enzyme activity in serum and FF was measured using the Chinard reagent via spectrophotometric analysis and compared between the groups.Results: Serum and FF prolidase levels were significantly lower in patients with PCOS (p < 0.05). A direct correlation was observed between serum and FF prolidase levels (p < 0.05). Although blastocyst quality scoring (BQS) significantly decreased in PCOS patients, no statistical difference was observed in the clinical pregnancy rate between the groups (p < 0.05) (p > 0.05). A negative correlation existed between serum prolidase levels and total antral follicle (AF) count (p < 0.05). Conversely, both serum and FF prolidase levels positively correlated with BQS (r = 0.574)(p < 0.05) (r = 0.650)(p < 0.05).Conclusions: Patients with PCOS showed lower serum and FF prolidase levels, indicating abnormal degradation of ovarian and follicular collagen, potentially causing anovulation.

Polycystic ovary syndrome (PCOS), the most prevalent endocrinopathy among reproductive-aged women, affects approximately 3­15% of this demographic. Long-term disorders such as cardiovascular disease, type 2 diabetes mellitus, obesity, and infertility are commonly associated with PCOS, with approximately 70% of affected women experiencing infertility. Although the aetiology of PCOS remains unclear, complex multigenic disorders and environmental factors such as abnormal ovarian extracellular matrix composition, disruption of the inflammatory pathway, and lifestyle factors have been found to be related.This study addresses the aetiology of PCOS, focusing on the close association between abnormal ovarian extracellular matrix composition and the syndrome, as seen in previous reports. Prolidase is a manganese-dependent cytosolic exopeptidase that degrades imidodipeptides using the C-terminal proline or hydroxyproline. Proline recycling from imidodipeptides by prolidase plays a critical role in the resynthesis of collagen and remodelling of the extracellular matrix. Our aim was to evaluate prolidase activity in the serum and follicular fluid of women diagnosed with PCOS. Our findings revealed a direct correlation between serum and follicular fluid prolidase levels, both of which were diminished in women with PCOS. Furthermore, a negative correlation was observed between serum prolidase levels and total antral follicle count indicating a potential link between prolidase activity and ovarian follicle development. In contrast, both serum and follicular fluid prolidase levels were positively correlated with blastocyst quality. In conclusion, PCOS patients showed lower serum and follicular fluid prolidase levels, indicating abnormal degradation of ovarian and follicular collagen, and potentially causing anovulation. Future studies measuring manganese levels in larger numbers of participants are required.

Urinary dipeptidase 1 and trefoil factor 1 are promising biomarkers for early diagnosis of colorectal cancer.

BACKGROUND: Currently utilized serum tumor markers and fecal immunochemical tests do not have sufficient diagnostic power for colorectal cancer (CRC) due to their low sensitivities. To establish non-invasive urinary protein biomarkers for early CRC diagnosis, we performed stepwise analyses employing urine samples from CRCs and healthy controls (HCs). METHODS: Among 474 urine samples, 363 age- and sex-matched participants (188 HCs, 175 stage 0-III CRCs) were randomly divided into discovery (16 HCs, 16 CRCs), training (110 HCs, 110 CRCs), and validation (62 HCs, 49 CRCs) cohorts. RESULTS: Of the 23 urinary protein candidates comprehensively identified from mass spectrometry in the discovery cohort, urinary levels of dipeptidase 1 (uDPEP1) and Trefoil factor1 (uTFF1) were the two most significant diagnostic biomarkers for CRC in both training and validation cohorts using enzyme-linked immunosorbent assays. A urinary biomarker panel comprising uDPEP1 and uTFF1 significantly distinguished CRCs from HCs, showing area under the curves of 0.825-0.956 for stage 0-III CRC and 0.792-0.852 for stage 0/I CRC. uDPEP1 and uTFF1 also significantly distinguished colorectal adenoma (CRA) patients from HCs, with uDPEP1 and uTFF1 increasing significantly in the order of HCs, CRA patients, and CRC patients. Moreover, expression levels of DPEP1 and TFF1 were also significantly higher in the serum and tumor tissues of CRC, compared to HCs and normal tissues, respectively. CONCLUSIONS: This study established a promising and non-invasive urinary protein biomarker panel, which enables the early detection of CRC with high sensitivity.

Dipeptidyl peptidases and E3 ligases of N-degron pathways cooperate to regulate protein stability.

N-degrons are short sequences located at protein N-terminus that mediate the interaction of E3 ligases (E3s) with substrates to promote their proteolysis. It is well established that N-degrons can be exposed following protease cleavage to allow recognition by E3s. However, our knowledge regarding how proteases and E3s cooperate in protein quality control mechanisms remains minimal. Using a systematic approach to monitor the protein stability of an N-terminome library, we found that proline residue at the third N-terminal position (hereafter "P+3") promotes instability. Genetic perturbations identified the dipeptidyl peptidases DPP8 and DPP9 and the primary E3s of N-degron pathways, UBR proteins, as regulators of P+3 bearing substrate turnover. Interestingly, P+3 UBR substrates are significantly enriched for secretory proteins. We found that secretory proteins relying on a signal peptide (SP) for their targeting contain a "built-in" N-degron within their SP. This degron becomes exposed by DPP8/9 upon translocation failure to the designated compartments, thus enabling clearance of mislocalized proteins by UBRs to maintain proteostasis.

State of the Art in the Development of Human Serum Carnosinase Inhibitors.

Human serum carnosinase is an enzyme that operates the preferential hydrolysis of dipeptides with a C-terminus histidine. Only higher primates excrete such an enzyme in serum and cerebrospinal fluid. In humans, the serum hydrolytic rate has high interindividual variability owing to gene polymorphism, although age, gender, diet, and also diseases and surgical interventions can modify serum activity. Human genetic diseases with altered carnosinase activity have been identified and associated with neurological disorders and age-related cognitive decline. On the contrary, low peripheral carnosinase activity has been associated with kidney protection, especially in diabetic nephropathy. Therefore, serum carnosinase is a druggable target for the development of selective inhibitors. However, only one molecule (i.e., carnostatine) has been discovered with the purpose of developing serum carnosinase inhibitors. Bestatin is the only inhibitor reported other than carnostatine, although its activity is not selective towards serum carnosinase. Herein, we present a review of the most critical findings on human serum carnosinase, including enzyme expression, localization and substrate selectivity, along with factors affecting the hydrolytic activity, its implication in human diseases and the properties of known inhibitors of the enzyme.

Immobilized Dipeptidase in Manganese Ion-Loaded Polyethylenimine-Induced Calcium Phosphate Nanocrystals for Carnosine Synthesis.

Carnosine is a natural bioactive dipeptide with important physiological functions widely used in food and medicine. Dipeptidase (PepD) from Serratia marcescens can catalyze the reverse hydrolytic reaction of ß-alanine with l-histidine to synthesize carnosine in the presence of Mn2+. However, it remains challenging to practice carnosine biosynthesis due to the low activity and high cost of the enzyme. Therefore, the development of biocatalysts with high activity and stability is of significance for carnosine synthesis. Here, we proposed to chelate Mn2+ to polyethylenimine (PEI) that induced rapid formation of calcium phosphate nanocrystals (CaP), and Mn-PEI@CaP was used for PepD immobilization via electrostatic interaction. Mn-PEI@CaP as the carrier enhanced the stability of the immobilized enzyme. Moreover, Mn2+ loaded in the carrier acted as an in situ activator of the immobilized PepD for facilitating the biocatalytic process of carnosine synthesis. The as-prepared immobilized enzyme (PepD-Mn-PEI@CaP) kept similar activity with free PepD plus Mn2+ (activity recovery, 102.5%), while exhibiting elevated thermal stability and pH tolerance. Moreover, it exhibited about two times faster carnosine synthesis than the free PepD system. PepD-Mn-PEI@CaP retained 86.8% of the original activity after eight cycles of batch catalysis without the addition of free Mn2+ ions during multiple cycles. This work provides a new strategy for the co-immobilization of PepD and Mn2+, which greatly improves the operability of the biocatalysis and demonstrates the potential of the immobilized PepD system for efficient carnosine synthesis.

Characterization and functional evidence for Orf2 of Streptomyces sp. 139 as a novel dipeptidase E.

Aspartyl dipeptidase (dipeptidase E) can hydrolyze Asp-X dipeptides (where X is any amino acid), and the enzyme plays a key role in the degradation of peptides as nutrient sources. Dipeptidase E remains uncharacterized in Streptomyces. Orf2 from Streptomyces sp. 139 is located in the exopolysaccharide biosynthesis gene cluster, which may be a novel dipeptidase E with "S134-H170-D198" catalytic triad by sequence and structure comparison. Herein, recombinant Orf2 was expressed in E. coli and characterized dipeptidase E activity using the Asp-ρNA substrate. The optimal pH and temperature for Orf2 are 7.5 and 40 ℃; Vmax and Km of Orf2 are 0.0787 mM·min-1 and 1.709 mM, respectively. Orf2 exhibits significant degradation activities to Asp-Gly-Gly, Asp-Leu, Asp-His, and isoAsp-Leu and minimal activities to Asp-Pro and Asp-Ala. Orf2 contains a Ser-His-Asp catalytic triad characterized by point mutation. In addition, the Asp147 residue of Orf2 is also proven to be critical for the enzyme's activity through molecular docking and point mutation. Transcriptome analysis reveals the upregulation of genes associated with ribosomes, amino acid biosynthesis, and aminoacyl-tRNA biosynthesis in the orf2 mutant strain. Compared with the orf2 mutant strain and WT, the yield of crude polysaccharide does not change significantly. However, crude polysaccharides from the orf2 mutant strain exhibit a wider range of molecular weight distribution. The results indicate that the Orf2 links nutrient stress to secondary metabolism as a novel dipeptidase E. KEY POINTS: • A novel dipeptidase E with a Ser-His-Asp catalytic triad was characterized from Streptomyces sp. 139. • Orf2 was involved in peptide metabolism both in vitro and in vivo. • Orf2 linked nutrient stress to mycelia formation and secondary metabolism in Streptomyces.

Identification and structure-based engineering of a dipeptidase CpPepD from Clostridium perfringens for the synthesis of l-carnosine.

l-Carnosine (l-Car), an endogenous dipeptide presents in muscle and brain tissues of various vertebrates, has a wide range of application values. The enzymatic preparation of l-Car is a promising synthetic method because it avoids the protection and deprotection steps. In the present study, a dipeptidase gene (CpPepD) from Clostridium perfringens with high l-Car synthetic activity was cloned and characterized. In an effort to improve the performance of this enzyme, we carried out site saturation mutagenesis using CpPepD as the template. By the o-phthalaldehyde (OPA)-derived high throughput screening method, mutant A171S was obtained with 2.2-fold enhanced synthetic activity. The enzymatic properties of CpPepD and mutant A171S were investigated. Under the optimized conditions, 63.94 mM (14.46 g L-1) or 67.02 mM (15.16 g L-1) l-Car was produced at the substrate concentrations of 6 M ß-Ala and 0.2 M l-His using wild-type or mutant A171S enzyme, respectively. Although the mutation enhanced the enzyme activity, the reaction equilibrium was barely affected.

Dipeptidase 1 promotes ferroptosis in renal tubular epithelial cells in diabetic nephropathy via inhibition of the GSH/GPX4 axis.

Renal tubular injury is an important pathological change associated with diabetic nephropathy (DN), in which ferroptosis of renal tubular epithelial cells is critical to its pathogenesis. Inhibition of the glutathione/glutathione peroxidase 4 (GSH/GPX4) axis is the most important mechanism in DN tubular epithelial cell ferroptosis, but the underlying reason for this is unclear. Our biogenic analysis showed that a zinc-dependent metalloproteinase, dipeptidase 1 (DPEP1), is associated with DN ferroptosis. Here, we investigated the role and mechanism of DPEP1 in DN tubular epithelial cell ferroptosis. DPEP1 upregulation was observed in the renal tubular epithelial cells of DN patients and model mice, as well as in HK-2 cells stimulated with high glucose. Furthermore, the level of DPEP1 upregulation was associated with the degree of tubular injury in DN patients and HK-2 cell ferroptosis. Mechanistically, knocking down DPEP1 expression could alleviate the inhibition of GSH/GPX4 axis and reduce HK-2 cell ferroptosis levels in a high glucose environment. HK-2 cells with stable DPEP1 overexpression also showed GSH/GPX4 axis inhibition and ferroptosis, but blocking the GSH/GPX4 axis could mitigate these effects. Additionally, treatment with cilastatin, a DPEP1 inhibitor, could ameliorate GSH/GPX4 axis inhibition and relieve ferroptosis and DN progression in DN mice. These results revealed that DPEP1 can promote ferroptosis in DN renal tubular epithelial cells via inhibition of the GSH/GPX4 axis.

Active site-directed probes targeting dipeptidyl peptidases 8 and 9.

Dipeptidyl peptidases (DPP) 8 and 9 are intracellular serine proteases that play key roles in various biological processes and recent findings highlight DPP8 and DPP9 as potential therapeutic targets for hematological and inflammasome-related diseases. Despite the substantial progress, the precise biological functions of these proteases remain elusive, and the lack of selective chemical tools hampers ongoing research. In this paper, we describe the synthesis and biochemical evaluation of the first active site-directed DPP8/9 probes which are derived from DPP8/9 inhibitors developed in-house. Specifically, we synthesized fluorescent inhibitors containing nitrobenzoxadiazole (NBD), dansyl (DNS) and cyanine-3 (Cy3) reporters to visualize intracellular DPP8/9. We demonstrate that the fluorescent inhibitors have high affinity and selectivity towards DPP8/9 over related S9 family members. The NBD-labeled DPP8/9 inhibitors were nominated as the best in class compounds to visualize DPP8/9 in human cells. Furthermore, a method has been developed for selective labeling and visualization of active DPP8/9 in vitro by fluorescence microscopy. A collection of potent and selective biotinylated DPP8/9-targeting probes was also prepared by replacing the fluorescent reporter with a biotin group. The present work provides the first DPP8/9-targeting fluorescent compounds as useful chemical tools for the study of DPP8 and DPP9's biological functions.

N2-Acetylornithine deacetylase functions as a Cys-Gly dipeptidase in the cytosolic glutathione degradation pathway in Arabidopsis thaliana.

Glutathione (GSH) is required for various physiological processes in plants, including redox regulation and detoxification of harmful compounds. GSH also functions as a repository for assimilated sulfur and is actively catabolized in plants. In Arabidopsis, GSH is mainly degraded initially by cytosolic enzymes, γ-glutamyl cyclotransferase, and γ-glutamyl peptidase, which release cysteinylglycine (Cys-Gly). However, the subsequent enzyme responsible for catabolizing this dipeptide has not been identified to date. In the present study, we identified At4g17830 as a Cys-Gly dipeptidase, namely cysteinylglycine peptidase 1 (CGP1). CGP1 complemented the phenotype of the yeast mutant that cannot degrade Cys-Gly. The Arabidopsis cgp1 mutant had lower Cys-Gly degradation activity than the wild type and showed perturbed concentrations of thiol compounds. Recombinant CGP1 showed reasonable Cys-Gly degradation activity in vitro. Metabolomic analysis revealed that cgp1 exhibited signs of severe sulfur deficiency, such as elevated accumulation of O-acetylserine (OAS) and the decrease in sulfur-containing metabolites. Morphological changes observed in cgp1, including longer primary roots of germinating seeds, were also likely associated with sulfur starvation. Notably, At4g17830 has previously been reported to encode an N2-acetylornithine deacetylase (NAOD) that functions in the ornithine biosynthesis. The cgp1 mutant did not show a decrease in ornithine content, whereas the analysis of CGP1 structure did not rule out the possibility that CGP1 has Cys-Gly dipeptidase and NAOD activities. Therefore, we propose that CGP1 is a Cys-Gly dipeptidase that functions in the cytosolic GSH degradation pathway and may play dual roles in GSH and ornithine metabolism.

Knock-out of dipeptidase CN2 in human proximal tubular cells disrupts dipeptide and amino acid homeostasis and para- and transcellular solute transport.

AIM: Although of potential biomedical relevance, dipeptide metabolism has hardly been studied. We found the dipeptidase carnosinase-2 (CN2) to be abundant in human proximal tubules, which regulate water and solute homeostasis. We therefore hypothesized, that CN2 has a key metabolic role, impacting proximal tubular transport function. METHODS: A knockout of the CN2 gene (CNDP2-KO) was generated in human proximal tubule cells and characterized by metabolomics, RNA-seq analysis, paracellular permeability analysis and ion transport. RESULTS: CNDP2-KO in human proximal tubule cells resulted in the accumulation of cellular dipeptides, reduction of amino acids and imbalance of related metabolic pathways, and of energy supply. RNA-seq analyses indicated altered protein metabolism and ion transport. Detailed functional studies demonstrated lower CNDP2-KO cell viability and proliferation, and altered ion and macromolecule transport via trans- and paracellular pathways. Regulatory and transport protein abundance was disturbed, either as a consequence of the metabolic imbalance or the resulting functional disequilibrium. CONCLUSION: CN2 function has a major impact on intracellular amino acid and dipeptide metabolism and is essential for key metabolic and regulatory functions of proximal tubular cells. These findings deserve in vivo analysis of the relevance of CN2 for nephron function and regulation of body homeostasis.

DPP8/9 inhibition attenuates the TGF-ß1-induced excessive deposition of extracellular matrix (ECM) in human mesangial cells via Smad and Akt signaling pathways.

The pathogenesis of glomerular diseases is strongly influenced by abnormal extracellular matrix (ECM) deposition in mesangial cells. Dipeptidyl peptidase IV (DPPIV) enzyme family contains DPP8 and DPP9, which are involved in multiple diseases. However, the pathogenic roles of DPP8 and DPP9 in mesangial cells ECM deposition remain unclear. In this study, we observed that DPP8 and DPP9 were significantly increased in glomerular mesangial cells and podocytes in CKD patients compared with healthy individuals, and DPP9 levels were higher in the urine of IgA nephropathy (IgAN) patients than in control urine. Therefore, we further explored the mechanism of DPP8 and DPP9 in mesangial cells and revealed a significant increase in the expression of DPP8 and DPP9 in human mesangial cells (HMCs) following TGF-ß1 stimulation. Silencing DPP8 and DPP9 by siRNAs alleviated the expression of ECM-related proteins including collagen Ⅲ, collagen Ⅳ, fibronectin, MMP2, in TGF-ß1-treated HMCs. Furthermore, DPP8 siRNA and DPP9 siRNA inhibited TGF-ß1-induced phosphorylation of Smad2 and Smad3, as well as the phosphorylation of Akt in HMCs. The findings suggested the inhibition of DPP8/9 may alleviate HMCs ECM deposition induced by TGF-ß1 via suppressing TGF-ß1/Smad and AKT signaling pathways.

Prolidase activity assays. A survey of the reported literature methodologies.

Prolidase (EC.3.4.13.9) is a dipeptidase known nowadays to play a pivotal role in several physiological and pathological processes. More in particular, this enzyme is involved in the cleavage of proline- and hydroxyproline-containing dipeptides (imidodipeptides), thus finely regulating the homeostasis of free proline and hydroxyproline. Abnormally high or low levels of prolidase have been found in numerous acute and chronic syndromes affecting humans (chronic liver fibrosis, viral and acute hepatitis, cancer, neurological disorders, inflammation, skin diseases, intellectual disability, respiratory infection, and others) for which the content of proline is well recognized as a clinical marker. As a consequence, the accurate analytical determination of prolidase activity is of greatly significant importance in clinical diagnosis and therapy. Apart from the Chinard's assay, some other more sensitive and well validated methodologies have been published. These include colorimetric and spectrophotometric determinations of free proline produced by enzymatic reactions, capillary electrophoresis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, electrochemoluminescence, thin layer chromatography, and HPLC. The aim of this comprehensive review is to make a detailed survey of the in so far reported analytical techniques, highlighting their general features, as well as their advantages and possible drawbacks, providing in the meantime suggestions to stimulate further research in this intriguing field.

Serum prolidase activity, oxidative stress, and antioxidant enzyme levels in patients with prostate cancer.

OBJECTIVES: We aimed to identify serum prolidase activity, oxidative stress, and antioxidant enzyme levels in patients with prostate cancers and to evaluate their relationships with each other. MATERIALS AND METHODS: A total of 34 male patients with prostate cancer and with a mean age of 64.2 ± 4.4 were included in the study. The control group comprising 36 male patients (mean age 61.2 ± 3.4) was randomly selected among the volunteers. Serum samples for measurement of superoxide dismutase (SOD), glutathione peroxidase (GPx), Catalase (CAT), malondialdehyde (MDA), glutathione (GSH), and prolidase levels were kept at -20°C until they were used. RESULTS: Serum prolidase activity and MDA levels were significantly higher in prostate cancer patients than in controls (all, P < 0.05), while SOD, GPx, and CAT levels were significantly lower (P < 0.05). CONCLUSION: Our results indicate that increased prolidase seems to be related to increased oxidative stress along with decreased antioxidant levels in prostate cancer.

Structural basis for the allosteric behaviour and substrate specificity of Lactococcus lactis Prolidase.

Prolidase (EC 3.4.13.9) is an enzyme that specifically hydrolyzes Xaa-Pro dipeptides into free amino acids. We previously studied kinetic behaviours and solved the crystal structure of wild-type (WT) Lactococcus lactis prolidase (Llprol), showing that this homodimeric enzyme has unique characteristics: allosteric behaviour and substrate inhibition. In this study, we focused on solving the crystal structures of three Llprol mutants (D36S, H38S, and R293S) which behave differently in v-S plots. The D36S and R293S Llprol mutants do not show allosteric behaviour, and the Llprol mutant H38S has allosteric behaviour comparable to the WT enzyme (Hill constant 1.52 and 1.58, respectively). The crystal structures of Llprol variants suggest that the active site of Llprol formed with amino acid residues from both monomers, i.e., located in an interfacial area of dimer. The comparison between the structure models of Llprol indicated that the two monomers in the dimers of Llprol variants have different relative positions among Llprol variants. They showed different interatomic distances between the amino acid residues bridging the two monomers and varied sizes of the solvent-accessible interface areas in each Llprol variant. These observations indicated that Llprol could adapt to different conformational states with distinctive substrate affinities. It is strongly speculated that the domain movements required for productive substrate binding are restrained in allosteric Llprol (WT and H38S). At low substrate concentrations, only one out of the two active sites at the dimer interface could accept substrate; as a result, the asymmetrical activated dimer leads to allosteric behaviour.

KLF6 activates Sp1-mediated prolidase transcription during TGF-ß1 signaling.

Prolidase (PEPD) is the only hydrolase that cleaves the dipeptides containing C-terminal proline or hydroxyproline-the rate-limiting step in collagen biosynthesis. However, the molecular regulation of prolidase expression remains largely unknown. In this study, we have identified overlapping binding sites for the transcription factors Krüppel-like factor 6 (KLF6) and Specificity protein 1 (Sp1) in the PEPD promoter and demonstrate that KLF6/Sp1 transcriptionally regulate prolidase expression. By cloning the PEPD promoter into a luciferase reporter and through site-directed deletion, we pinpointed the minimal sequences required for KLF6 and Sp1-mediated PEPD promoter-driven transcription. Interestingly, Sp1 inhibition abrogated KLF6-mediated PEPD promoter activity, suggesting that Sp1 is required for the basal expression of prolidase. We further studied the regulation of PEPD by KLF6 and Sp1 during transforming growth factor ß1 (TGF-ß1) signaling, since both KLF6 and Sp1 are key players in TGF-ß1 mediated collagen biosynthesis. Mouse and human fibroblasts exposed to TGF-ß1 resulted in the induction of PEPD transcription and prolidase expression. Inhibition of TGF-ß1 signaling abrogated PEPD promoter-driven transcriptional activity of KLF6 and Sp1. Knock-down of KLF6 as well as Sp1 inhibition also reduced prolidase expression. Chromatin immunoprecipitation assay supported direct binding of KLF6 and Sp1 to the PEPD promoter and this binding was enriched by TGF-ß1 treatment. Finally, immunofluorescence studies showed that KLF6 co-operates with Sp1 in the nucleus to activate prolidase expression and enhance collagen biosynthesis. Collectively, our results identify functional elements of the PEPD promoter for KLF6 and Sp1-mediated transcriptional activation and describe the molecular mechanism of prolidase expression.

Human carnosinases: A brief history, medicinal relevance, and in silico analyses.

Carnosine, an endogenous dipeptide, has been found to have a plethora of medicinal properties, such as antioxidant, antiageing, and chelating effects, but with one downside: a short half-life. Carnosinases and two hydrolytic enzymes, which remain enigmatic, are responsible for these features. Hence, here we emphasize why research is valuable for better understanding crucial concepts like ageing, neurodegradation, and cancerogenesis, given that inhibition of carnosinases might significantly prolong carnosine bioavailability and allow its further use in medicine. Herein, we explore the literature regarding carnosinases and present a short in silico analysis aimed at elucidating the possible recognition pattern between CN1 and its ligands.

Dipeptidase­2 is a prognostic marker in lung adenocarcinoma that is correlated with its sensitivity to cisplatin.

Lung cancer accounts for the highest percentage of cancer morbidity and mortality worldwide, and lung adenocarcinoma (LUAD) is the most prevalent subtype. Although numerous therapies have been developed for lung cancer, patient prognosis is limited by tumor metastasis and more effective treatment targets are urgently required. In the present study, gene expression profiles were extracted from the Gene Expression Omnibus database and mRNA expression data were downloaded from The Cancer Genome Atlas database. In addition, TIMER 2.0 database was used to analyze the expression of genes in normal and multiple tumor tissues. Protein expression was confirmed using the Human Protein Atlas database and LUAD cell lines, sphere formation assay, western blotting, and a xenograft mouse model were used to confirm the bioinformatics analysis. Dipeptidase­2 (DPEP2) expression was significantly decreased in LUAD and was negatively associated with prognosis. DPEP2 overexpression substantially inhibited epithelial­mesenchymal transition (EMT) as well as LUAD cell metastasis, and limited the expression of the cancer stem cell transformation markers, CD44 and CD133. In addition, DPEP2 improved LUAD sensitivity to cisplatin by inhibiting EMT; this was verified in vitro and in vivo. These data indicated that DPEP2 upregulates E­cadherin, thereby regulating cell migration, cancer stem cell transformation, and cisplatin resistance, ultimately affecting the survival of patients with LUAD. Overall, the findings of the present suggest that DPEP2 is important in the development of LUAD and can be used both as a prognostic marker and a target for future therapeutic research.

Association of Metformin, Dipeptidyl Dipeptidase-4 Inhibitors, and Insulin with Coronavirus Disease 2019-Related Hospital Outcomes in Patients with Type 2 Diabetes.

OBJECTIVE: The effects of diabetes medications on COVID-19 hospitalization outcomes have not been consistent. We sought to determine the effect of metformin, dipeptidyl peptidase-4 inhibitors (DPP-4i), and insulin on admission to the intensive care unit (ICU), need for assisted ventilation, development of renal insufficiency, and mortality in patients admitted with COVID-19 infection after controlling for clinical variables and other relevant diabetes-related medications in patients with type 2 diabetes mellitus (DM). METHODS: This was a retrospective study of patients hospitalized with COVID-19 from a single hospital system. Univariate and multivariate analyses were performed that included demographic data, glycated hemoglobin, kidney function, smoking status, insurance, Charlson comorbidity index, number of diabetes medications, and use of angiotensin-converting enzyme inhibitors and statin prior to admission and glucocorticoids during admission. RESULTS: A total of 529 patients with type 2 DM were included in our final analysis. Neither metformin nor DPP4i prescription was associated with ICU admission, need for assisted ventilation, or mortality. Insulin prescription was associated with increased ICU admission but not with need for assisted ventilation or mortality. There was no association of any of these medications with development of renal insufficiency. CONCLUSIONS: In this population, limited to type 2 DM and controlled for multiple variables that have not been consistently studied (such as a measure of general health, glycated hemoglobin, and insurance status), insulin prescription was associated with increased ICU admission. Metformin and DPP4i prescriptions did not have an association with the outcomes.