Prolidase function in proline metabolism and its medical and biotechnological applications

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.

KLF6 activates Sp1-mediated prolidase transcription during TGF-β1 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 β1 (TGF-β1) signaling, since both KLF6 and Sp1 are key players in TGF-β1 mediated collagen biosynthesis. Mouse and human fibroblasts exposed to TGF-β1 resulted in the induction of PEPD transcription and prolidase expression. Inhibition of TGF-β1 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-β1 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.

Can proline dehydrogenase-a key enzyme involved in proline metabolism-be a novel target for cancer therapy?

Emerging evidence suggests that proline metabolism is important for regulating the survival and death of different types of cancer cells. Proline dehydrogenase (PRODH), an enzyme catalyzing proline catabolism, and the degradation products of proline by PRODH, such as ATP and ROS, are known to play critical roles in cancer progression. Notably, the role of PRODH in cancer is still complicated and unclear, and primarily depends on the cancer type and tumor microenvironment. For instance, PRODH induces apoptosis and senescence through ROS signaling in different types of cancers, while as a protumor factor, PRODH promotes malignant phenotypes of certain tumors under stresses such as hypoxia. In order to assess whether PRODH can serve as a novel target for cancer therapy, we will provide an overview of the biological functions of PRODH and its double-edged role in cancer in this article.

Proline catabolism is a key factor facilitating Candida albicans pathogenicity

Candida albicans, the primary etiology of human mycoses, is well-adapted to catabolize proline to obtain energy to initiate morphological switching (yeast to hyphal) and for growth. We report that put1-/- and put2-/- strains, carrying defective Proline UTilization genes, display remarkable proline sensitivity with put2-/- mutants being hypersensitive due to the accumulation of the toxic intermediate pyrroline-5-carboxylate (P5C), which inhibits mitochondrial respiration. The put1-/- and put2-/- mutations attenuate virulence in Drosophila and murine candidemia models and decrease survival in human neutrophils and whole blood. Using intravital 2-photon microscopy and label-free non-linear imaging, we visualized the initial stages of C. albicans cells infecting a kidney in real-time, directly deep in the tissue of a living mouse, and observed morphological switching of wildtype but not of put2-/- cells. Multiple members of the Candida species complex, including C. auris, are capable of using proline as a sole energy source. Our results indicate that a tailored proline metabolic network tuned to the mammalian host environment is a key feature of opportunistic fungal pathogens.

Hydroxyproline metabolism enhances IFN-γ-induced PD-L1 expression and inhibits autophagic flux

The immune checkpoint protein PD-L1 plays critical roles in both immune system homeostasis and tumor progression. Impaired PD-1/PD-L1 function promotes autoimmunity and PD-L1 expression within tumors promotes immune evasion. If and how changes in metabolism or defined metabolites regulate PD-L1 expression is not fully understood. Here, using a metabolomics activity screening-based approach, we have determined that hydroxyproline (Hyp) significantly and directly enhances adaptive (i.e., IFN-γ-induced) PD-L1 expression in multiple relevant myeloid and cancer cell types. Mechanistic studies reveal that Hyp acts as an inhibitor of autophagic flux, which allows it to regulate this negative feedback mechanism, thereby contributing to its overall effect on PD-L1 expression. Due to its prevalence in fibrotic tumors, these findings suggest that hydroxyproline could contribute to the establishment of an immunosuppressive tumor microenvironment and that Hyp metabolism could be targeted to pharmacologically control PD-L1 expression for the treatment of cancer or autoimmune diseases.

Defective extracellular matrix remodeling in brown adipose tissue is associated with fibro-inflammation and reduced diet-induced thermogenesis

The relevance of extracellular matrix (ECM) remodeling is reported in white adipose tissue (AT) and obesity-related dysfunctions, but little is known about the importance of ECM remodeling in brown AT (BAT) function. Here, we show that a time course of high-fat diet (HFD) feeding progressively impairs diet-induced thermogenesis concomitantly with the development of fibro-inflammation in BAT. Higher markers of fibro-inflammation are associated with lower cold-induced BAT activity in humans. Similarly, when mice are housed at thermoneutrality, inactivated BAT features fibro-inflammation. We validate the pathophysiological relevance of BAT ECM remodeling in response to temperature challenges and HFD using a model of a primary defect in the collagen turnover mediated by partial ablation of the Pepd prolidase. Pepd-heterozygous mice display exacerbated dysfunction and BAT fibro-inflammation at thermoneutrality and in HFD. Our findings show the relevance of ECM remodeling in BAT activation and provide a mechanism for BAT dysfunction in obesity.

Prolidase deficiency: A novel PEPD missense variant in exon 2

Prolidase deficiency is an autosomal recessive disease that causes impaired collagen degradation. Altered collagen homeostasis results in the intracellular accumulation of imidodipeptides, which contain proline and hydroxyproline. The many clinical manifestations of prolidase deficiency include dysmorphic facial features, skeletal deformities, hepatosplenomegaly, necrotizing skin ulcers, and recurrent infections. Current clinical knowledge of this genetic disease relies upon few case reports due to its extreme rarity. Diagnosis is dependent on the detection of a pathologic gene variant. Additional diagnostic confirmation may be provided by urine amino acid quantification or reduced in vitro prolidase activity. We present a case of prolidase deficiency caused by a novel variant manifested by skeletal malformations and lifelong multisystemic infections. Genetic testing revealed a homozygous missense variant in the PEPD gene at nucleotide position 200, whereby adenine was replaced by guanine (c.200A > G). The corresponding amino acid change replaced glutamine with arginine at codon 67 (p.Gln67Arg). After boiling the urine sample for hydrolysis, quantitative urine amino acids demonstrated a markedly elevated proline level, confirming the diagnosis. We also provide a discussion of the pathophysiology, clinical manifestations, diagnostic testing, and clinical management of this disease.

Prolidase as a marker of fibrogenesis in idiopathic primary ovarian insufficiency

OBJECTIVES

To evaluate the serumlevel of prolidase,which isa marker of fibrogenic activity, in women with idiopathic primary ovarian insufficiency (POI).

STUDY DESIGN

This is a prospective case-control study. Serum prolidase level was compared between the study group including 68 women with POI and control group including 65 normally menstruating women. Serum proline and hydroxyproline levels were also compared. Correlation analyses were performed between the prolidase level and POI related parameters including estradiol (E), follicle stimulating hormone (FSH), anti-mullerian hormone (AMH) levels, and presence of POI family history.

RESULTS

Serum prolidase and proline level were significantly increased in women with the diagnosis of POI compared to the control group (1082.57 (147.53) vs 981.13 (223.26) U/L, 233.30 (83.16) vs 218.94 (82.59) µmol/L, respectively). Prolidase level found to have significant correlations with AMH, E, FSH levels, and presence of POI family history (r = -0.49, p = 0.001; r = -0.39, p = 0.001; r = 0.42, p = 0.001; r = 0.22, p = 0.01; respectively). In receiver operating characteristics analysis, prolidase was shown to be a discriminative factor for POI at 1031.14 U/L cut-off value with 75 % sensitivity and 65 % specificity. Thearea under curve was 0.71 [(95 % CI: 0.62-0.79), p = 0.001].

CONCLUSION

The current study revealed increased prolidase level in women withPOI. Serum prolidase level was also negatively correlated with the serum AMH level. Considering the present findings,prolidase may be a candidate molecule in assessment of POI cases.

Next-generation sequencing of prolidase gene identifies novel and common variants associated with low prolidase in coronary artery ectasia

BACKGROUND

Decreased collagen biosynthesis and increased collagenolysis can cause ectasia progression in the arterial walls. Prolidase is a key enzyme in collagen synthesis; a decrease in prolidase activity or level may decrease collagen biosynthesis, which may contribute to ectasia formation. Considering that, the variations in PEPD gene encoding prolidase enzyme were evaluated by analyzing next-generation sequencing (NGS) for the first time together with known risk factors in coronary artery ectasia (CAE) patients.

METHODS

Molecular analysis of the PEPD gene was performed on genomic DNA by NGS in 76 CAE patients and 76 controls. The serum levels of prolidase were measured by the sandwich-ELISA technique.

RESULTS

Serum prolidase levels were significantly lower in CAE group compared to control group, and it was significantly lower in males than females in both groups (p < 0.001). On the other hand, elevated prolidase levels were observed in CAE patients in the presence of diabetes (p < 0.001), hypertension (p < 0.05) and hyperlipidemia (p < 0.05). Logistic regression analysis demonstrated that the low prolidase level (p < 0.001), hypertension (p < 0.02) and hyperlipidemia (p < 0.012) were significantly associated with increased CAE risk. We identified four missense mutations in the PEPD gene, namely G296S, T266A, P365L and S134C (novel) that could be associated with CAE. The pathogenicity of these mutations was predicted to be "damaging" for G296S, S134C and P365L, but "benign" for T266A. We also identified a novel 5'UTR variation (Chr19:34012748 G>A) in one patient who had a low prolidase level. In addition, rs17570 and rs1061338 common variations of the PEPD gene were associated with low prolidase levels in CAE patients, while rs17569 variation was associated with high prolidase levels in both CAE and controls (p < 0.05).

CONCLUSIONS

Our findings indicate that the low serum prolidase levels observed in CAE patients is significantly associated with PEPD gene variations. It was concluded that low serum prolidase level and associated PEPD mutations may be potential biomarkers for the diagnosis of CAE.

Recombinant Human Prolidase (rhPEPD) Induces Wound Healing in Experimental Model of Inflammation through Activation of EGFR Signalling in Fibroblasts

The potential of recombinant human prolidase (rhPEPD) to induce wound healing in an experimental model of IL-1β-induced inflammation in human fibroblasts was studied. It was found that rhPEPD significantly increased cell proliferation and viability, as well as the expression of the epidermal growth factor receptor (EGFR) and downstream signaling proteins, such as phosphorylated PI3K, AKT, and mTOR, in the studied model. Moreover, rhPEPD upregulated the expression of the β1 integrin receptor and its downstream signaling proteins, such as p-FAK, Grb2 and p-ERK 1/2. The inhibition of EGFR signaling by gefitinib abolished rhPEPD-dependent functions in an experimental model of inflammation. Subsequent studies showed that rhPEPD augmented collagen biosynthesis in IL-1β-treated fibroblasts as well as in a wound healing model (wound closure/scratch test). Although IL-1β treatment of fibroblasts increased cell migration, rhPEPD significantly enhanced this process. This effect was accompanied by an increase in the activity of MMP-2 and MMP-9, suggesting extracellular matrix (ECM) remodeling during the inflammatory process. The data suggest that rhPEPD may play an important role in EGFR-dependent cell growth in an experimental model of inflammation in human fibroblasts, and this knowledge may be useful for further approaches to the treatment of abnormalities of wound healing and other skin diseases.

Discovering new peripheral plasma biomarkers to identify cognitive decline in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is an independent risk factor of Alzheimer's disease (AD), and thus identifying who among the increasing T2DM populations may develop into AD is important for early intervention. By using TMT-labeling coupled high-throughput mass spectrometry, we conducted a comprehensive plasma proteomic analysis in none-T2DM people (Ctrl, n = 30), and the age-/sex-matched T2DM patients with mild cognitive impairment (T2DM-MCI, n = 30) or T2DM without MCI (T2DM-nMCI, n = 25). The candidate biomarkers identified by proteomics and bioinformatics analyses were verified by ELISA, and their diagnostic capabilities were evaluated with machine learning. A total of 53 differentially expressed proteins (DEPs) were identified in T2DM-MCI compared with T2DM-nMCI patients. These DEPs were significantly enriched in multiple biological processes, such as amyloid neuropathies, CNS disorders, and metabolic acidosis. Among the DEPs, alpha-1-antitrypsin (SERPINA1), major viral protein (PRNP), and valosin-containing protein (VCP) showed strong correlation with AD high-risk genes APP, MAPT, APOE, PSEN1, and PSEN2. Also, the levels of PP2A cancer inhibitor (CIP2A), PRNP, corticotropin-releasing factor-binding protein (CRHBP) were significantly increased, while the level of VCP was decreased in T2DM-MCI patients compared with that of the T2DM-nMCI, and these changes were correlated with the Mini-Mental State Examination (MMSE) score. Further machine learning data showed that increases in PRNP, CRHBP, VCP, and rGSK-3β(T/S9) (ratio of total to serine-9-phosphorylated glycogen synthase kinase-3β) had the greatest power to identify mild cognitive decline in T2DM patients.

Effectual Endeavors of Silk Protein Sericin against Isoproterenol Induced Cardiac Toxicity and Hypertrophy in Wistar Rats

The silkworm cocoon has been used in the treatment of various ailments in different Asian countries. This research was designed to evaluate the effect of sericin on myocardial necrosis and hypertrophy in isoproterenol-challenged rats. The rats were administered with sericin (500 and 1000 mg/kg, p.o.) for 28 days, followed by administration of isoprenaline (85 mg/kg, s.c.) on the 29th and 30th days. The cardioprotective activity was assessed by various physical, enzymatic, and histopathological parameters along with apoptotic marker expression. The cardioprotective effect showed that pre-treatment of rats with sericin significantly increased the non-enzymatic antioxidants marker in serum and heart tissue (glutathione, vitamin E, and vitamin C). The results were the same in enzymatic antioxidant marker, mitochondrial enzymes, and protein. The grading of heart, heart/body weight ratio, gross morphology, cardiac markers, oxidative stress markers in serum and heart tissue, glucose, serum lipid profiling and Lysosomal hydrolases, heart apoptotic markers such as MHC expression by western blot, apoptosis by flow cytometry, total myocardial collagen content, fibrosis estimation, myocyte size were significantly decreased when compared with isoproterenol (ISG) group however histopathological studies showed normal architecture of heart in both control and treated rats. The pharmacological study reflects that sericin on both doses i.e., 500 mg/kg and 1000 mg/kg have potent cardioprotective action against the experimental model which was confirmed by various physical, biochemical, and histopathological parameters evaluated further research is required to examine the molecular mechanism of cardioprotective effect of sericin.

Peptidomics as a useful tool in the follow-up of food bioactive peptides

There is an intense research activity on bioactive peptides derived from food proteins in view of their health benefits for consumers. However, their identification is quite challenging as a consequence of their small size and low abundance in complex matrices such as foods or hydrolyzates. Recent advances in peptidomics and bioinformatics are getting improved sensitivity and accuracy and therefore such tools are contributing to the development of sophisticated methodologies for the identification and quantification of peptides. These developments are very useful for the follow-up of peptides released through proteolysis either in the food itself through the action of endogenous peptidases during processing stages like fermentation, drying or ripening, or from food proteins hydrolyzed by commercial peptidases or microorganisms with proteolytic activity. This chapter is presenting the latest advances in peptidomics and its use for the identification and quantification of peptides, and as a useful tool for controlling the proteolysis phenomena in foods and protein hydrolyzates.

Dysregulation of macrophage PEPD in obesity determines adipose tissue fibro-inflammation and insulin resistance

Resulting from impaired collagen turnover, fibrosis is a hallmark of adipose tissue (AT) dysfunction and obesity-associated insulin resistance (IR). Prolidase, also known as peptidase D (PEPD), plays a vital role in collagen turnover by degrading proline-containing dipeptides but its specific functional relevance in AT is unknown. Here we show that in human and mouse obesity, PEPD expression and activity decrease in AT, and PEPD is released into the systemic circulation, which promotes fibrosis and AT IR. Loss of the enzymatic function of PEPD by genetic ablation or pharmacological inhibition causes AT fibrosis in mice. In addition to its intracellular enzymatic role, secreted extracellular PEPD protein enhances macrophage and adipocyte fibro-inflammatory responses via EGFR signalling, thereby promoting AT fibrosis and IR. We further show that decreased prolidase activity is coupled with increased systemic levels of PEPD that act as a pathogenic trigger of AT fibrosis and IR. Thus, PEPD produced by macrophages might serve as a biomarker of AT fibro-inflammation and could represent a therapeutic target for AT fibrosis and obesity-associated IR and type 2 diabetes.

Recombinant Prolidase Activates EGFR-Dependent Cell Growth in an Experimental Model of Inflammation in HaCaT Keratinocytes. Implication for Wound Healing

This study was conducted to investigate the proliferative capacity of recombinant human prolidase (rhPEPD) in a human model of inflammation induced by IL-1β in HaCaT keratinocytes. In this report, we provide evidence that IL-1β stimulates keratinocyte proliferation, and rhPEPD significantly augmented this process through activation of epidermal growth factor receptor (EGFR) and downstream signaling proteins as phosphorylated Akt, ERK1/2, and STAT3, which are implicated in keratinocyte migration, proliferation, and epithelialization during the wound healing process. Inhibition of PEPD-dependent EGFR signaling by gefitinib supported the finding. Moreover, during activation of EGFR in the presence of IL-1β the epithelial-to-mesenchymal transition (EMT) occurred via downregulation of E-cadherin and upregulation of N-cadherin. The phenomenon was accompanied by an increase in the activity of matrix metalloproteinase-9 (MMP-9), suggesting extracellular matrix (ECM) remodeling during the inflammatory process. MMP-9 activation may result from nuclear translocation of NF-κB through IKK-mediated IκBα degradation. Interestingly, some mutated variants of PEPD (rhPEPD-G448R, rhPEPD-231delY, and rhPEPD-E412K) evoked the ability to induce EGFR-dependent HaCaT cell proliferation. To the best of our knowledge, this is the first report on the cross-talk between PEPD and IL-1β in the process of keratinocyte proliferation. The data suggest that both enzymatically active and inactive rhPEPD may activate EGFR-dependent cell growth in an experimental model of inflammation in HaCaT keratinocytes and the knowledge may be useful for further approaches for therapy of wound healing disorders.

Genomic Characterization of Parengyodontium torokii sp. nov., a Biofilm-Forming Fungus Isolated from Mars 2020 Assembly Facility

A fungal strain (FJII-L10-SW-P1) was isolated from the Mars 2020 spacecraft assembly facility and exhibited biofilm formation on spacecraft-qualified Teflon surfaces. The reconstruction of a six-loci gene tree (ITS, LSU, SSU, RPB1 and RPB2, and TEF1) using multi-locus sequence typing (MLST) analyses of the strain FJII-L10-SW-P1 supported a close relationship to other known Parengyodontium album subclade 3 isolates while being phylogenetically distinct from subclade 1 strains. The zig-zag rachides morphology of the conidiogenous cells and spindle-shaped conidia were the distinct morphological characteristics of the P. album subclade 3 strains. The MLST data and morphological analysis supported the conclusion that the P. album subclade 3 strains could be classified as a new species of the genus Parengyodontium and placed in the family Cordycipitaceae. The name Parengyodontium torokii sp. nov. is proposed to accommodate the strain, with FJII-L10-SW-P1 as the holotype. The genome of the FJII-L10-SW-P1 strain was sequenced, annotated, and the secondary metabolite clusters were identified. Genes predicted to be responsible for biofilm formation and adhesion to surfaces were identified. Homology-based assignment of gene ontologies to the predicted proteome of P. torokii revealed the presence of gene clusters responsible for synthesizing several metabolic compounds, including a cytochalasin that was also verified using traditional metabolomic analysis.

OUP accepted manuscript

Objective

The aim of the study was to evaluate proline metabolism in patients affected by COVID-19.

Materials and Methods

This case-control study consisted of 116 patients with COVID-19 and 46 healthy individuals. Tests related to proline metabolism (prolidase, proline, hydroxyproline, glutamic acid, manganese) and copper and zinc tests were analyzed.

Results

The levels of proline and hydroxyproline amino acids and the prolidase enzyme were found to be lower and glutamic acid was found to be higher in the COVID-19 group compared to the healthy group (P = .012, P < .001, P < .001, and P < .001, respectively). The copper/zinc ratio was higher in patients with COVID-19 than in healthy individuals (P < .001). Significant correlations were found between proline metabolism tests and inflammatory and hemostatic markers commonly used in COVID-19.

Conclusion

The proline metabolic pathway was affected in COVID-19. Relationships between proline pathway–related tests and inflammatory/hemostatic markers supported the roles of proline metabolism in proinflammatory and immune response processes.

Activation of proline metabolism maintains ATP levels during cocaine-induced polyADP-ribosylation

Cocaine is a commonly abused drug worldwide. Acute as well as repeated exposure to cocaine activates persistent cellular and molecular changes in the brain reward regions. The effects of cocaine are predominantly mediated via alterations in neuronal gene expression by chromatin remodeling. Poly(ADP-ribose) polymerase-1 (PARP-1) catalyzed PARylation of chromatin has been reported as an important regulator of cocaine-mediated gene expression. PARP-1 dependent ADP-ribosylation is an energy-dependent process. In this study, we investigated the cellular energy response to cocaine-induced upregulation of PARP-1 expression. Exposure of differentiated SH-SY5Y cells to varying concentrations of cocaine resulted in the induction of PARP-1 dependent PARylation of p53 tumor suppressor. Further analysis revealed that PARylation of p53 by cocaine treatment resulted in nuclear accumulation of p53. However, induction and nuclear accumulation of p53 did not correlate with neuronal apoptosis/cell death upon cocaine exposure. Interestingly, cocaine-induced p53 PARylation resulted in the induction of proline oxidase (POX)—a p53 responsive gene involved in cellular metabolism. Given that cocaine-induced p53 PARylation is an energy-dependent process, we observed that cocaine-induced PARP-1/p53/POX axes alters cellular energy metabolism. Accordingly, using pharmacological and genetic studies of PARP-1, p53, and POX, we demonstrated the contribution of POX in maintaining cellular energy during neuronal function. Collectively, these studies highlight activation of a novel metabolic pathway in response to cocaine treatment.

Oxidative Stress and Musculoskeletal Pain in University Students with Generalized Joint Hypermobility: A Case-Control Study

Objective

The current case–control study aimed to evaluate generalized joint hypermobility (GJH) and its association with pain intensity, cellular oxidative stress, and collagen-associated disorders in university students aged 18–25 years old.

Background

Joint hypermobility has been recognized in healthy subjects and people who are carriers of cellular disorders in connective tissues. Cellular tissue oxidative stress and collagen-associated disorders were shown to be associated with joint hypermobility (JH).

Materials and Methods

A total of 300 university students aged 18–25 years were randomly invited from different medical and science faculties in Mansoura university, Mansoura, Egypt to participate in this case–control study. Only 280 university students who had no exclusion criteria like chronic health problems, physical disability, musculoskeletal disorders, and body mass index (BMI) of ≥25 underwent an initial clinical interview and Beighton scoring as measures of GJH. Pain intensity, physical activity, oxidative stress parameters; TAC, TOC, OSI, and collagen-associated parameters; cellular prolidase activity and hydroxyproline were evaluated by using a prevalidated questionnaire, colorimetric, and immunoassay techniques.

Results

GJH was significantly reported in 57.1% of the study population, and most of them are females. Compared to men, females with GJH showed poor physical activity, lower TAC, and significantly higher levels of TOC, OSI, cellular prolidase activity, and hydroxyproline. Based on our findings, a high Beighton score is closely related to the tissue levels of prolidase, hydroxyproline, antioxidant activity, pain intensity, and poor physical activity in the female with GJH compared to men.

Conclusion

GJH was significantly reported in 57.1% of the study population, and most of them are females. The incidence of GJH showed to be associated with poor physical activity, abnormal cellular oxidative stress, and collagen abnormalities measured by significant increase in change in cellular prolidase activity and hydroxyproline.

Genetic architecture of 11 organ traits derived from abdominal MRI using deep learning

Cardiometabolic diseases are an increasing global health burden. While socioeconomic, environmental, behavioural, and genetic risk factors have been identified, a better understanding of the underlying mechanisms is required to develop more effective interventions. Magnetic resonance imaging (MRI) has been used to assess organ health, but biobank-scale studies are still in their infancy. Using over 38,000 abdominal MRI scans in the UK Biobank, we used deep learning to quantify volume, fat, and iron in seven organs and tissues, and demonstrate that imaging-derived phenotypes reflect health status. We show that these traits have a substantial heritable component (8-44%) and identify 93 independent genome-wide significant associations, including four associations with liver traits that have not previously been reported. Our work demonstrates the tractability of deep learning to systematically quantify health parameters from high-throughput MRI across a range of organs and tissues, and use the largest-ever study of its kind to generate new insights into the genetic architecture of these traits.

Proline metabolism and transport in retinal health and disease

The retina is one of the most energy-demanding tissues in the human body. Photoreceptors in the outer retina rely on nutrient support from the neighboring retinal pigment epithelium (RPE), a monolayer of epithelial cells that separate the retina and choroidal blood supply. RPE dysfunction or cell death can result in photoreceptor degeneration, leading to blindness in retinal degenerative diseases including some inherited retinal degenerations and age-related macular degeneration (AMD). In addition to having ready access to rich nutrients from blood, the RPE is also supplied with lactate from adjacent photoreceptors. Moreover, RPE can phagocytose lipid-rich outer segments for degradation and recycling on a daily basis. Recent studies show RPE cells prefer proline as a major metabolic substrate, and they are highly enriched for the proline transporter, SLC6A20. In contrast, dysfunctional or poorly differentiated RPE fails to utilize proline. RPE uses proline to fuel mitochondrial metabolism, synthesize amino acids, build the extracellular matrix, fight against oxidative stress, and sustain differentiation. Remarkably, the neural retina rarely imports proline directly, but it uptakes and utilizes intermediates and amino acids derived from proline catabolism in the RPE. Mutations of genes in proline metabolism are associated with retinal degenerative diseases, and proline supplementation is reported to improve RPE-initiated vision loss. This review will cover proline metabolism in RPE and highlight the importance of proline transport and utilization in maintaining retinal metabolism and health.

The Serum Prolidase Enzyme Activity as a Biomarker for Evaluation of the Subclinical Vascular Damage in Children with Epilepsy

Backgroud:

Epilepsy is a chronic medical condition requiring long term or even lifelong therapy. Various researches have shown that epilepsy patients have vascular risk factors such as abnormal lipids, insulin, elevated oxidative stress, chronic inflammation, and subclinical atherosclerosis.

Objectives:

The purpose of the present study was to determine serum prolidase enzyme activity as a biomarker in children taking antiepileptic drug treatment through comparison with control cases.

Materials and Methods:

The present study group consists of 61 children (20 females, 41 males) with epilepsy and a control group was formed of 32 healthy individuals (14 females, 18 males). Aspectrophotometric method was used to measure serum prolidase enzyme activity.

Results:

The epilepsy group demonstrated statistically significantly higher prolidase enzyme activity values when compared with the control group (P = 0.003). It was measured that the serum TOS and OSI values were significantly elevated in patients with epilepsy compared to controls (P < 0.001). However, serum TAS values were significantly lower in the epilepsy group than in the control group (P = 0.032).

Conclusions:

These results supported that epileptic patients taking the antiepileptic treatment had increased serum prolidase enzyme activity, suggesting that it may show an increased risk of subclinical vascular damage related to both chronic inflammation and fibrotic process associated with degenerated collagen turnover. Therefore, serum prolidase enzyme activity could be considered a useful biomarker for evaluation of the subclinical vascular damage in children with epilepsy on some antiepileptic drugs.

Clostridioides difficile exploits toxin-mediated inflammation to alter the host nutritional landscape and exclude competitors from the gut microbiota

Clostridioides difficile is a bacterial pathogen that causes a range of clinical disease from mild to moderate diarrhea, pseudomembranous colitis, and toxic megacolon. Typically, C. difficile infections (CDIs) occur after antibiotic treatment, which alters the gut microbiota, decreasing colonization resistance against C. difficile. Disease is mediated by two large toxins and the expression of their genes is induced upon nutrient depletion via the alternative sigma factor TcdR. Here, we use tcdR mutants in two strains of C. difficile and omics to investigate how toxin-induced inflammation alters C. difficile metabolism, tissue gene expression and the gut microbiota, and to determine how inflammation by the host may be beneficial to C. difficile. We show that C. difficile metabolism is significantly different in the face of inflammation, with changes in many carbohydrate and amino acid uptake and utilization pathways. Host gene expression signatures suggest that degradation of collagen and other components of the extracellular matrix by matrix metalloproteinases is a major source of peptides and amino acids that supports C. difficile growth in vivo. Lastly, the inflammation induced by C. difficile toxin activity alters the gut microbiota, excluding members from the genus Bacteroides that are able to utilize the same essential nutrients released from collagen degradation.

The effects of antibiotics on the gut microbiota can lead to enhanced colonization of Clostridioides difficile (C. difficile) and toxin-mediated pathogenesis. Here, using defined toxin-mutant strains and a murine model, the authors provide insights into how toxin-induced inflammation alters C. difficile metabolism, host tissue gene expression and gut microbiota, together influencing a beneficial niche for infection.

Extracellular Prolidase (PEPD) Induces Anabolic Processes through EGFR, β1-integrin, and IGF-1R Signaling Pathways in an Experimental Model of Wounded Fibroblasts

The role of prolidase (PEPD) as a ligand of the epidermal growth factor receptor (EGFR) was studied in an experimental model of wound healing in cultured fibroblasts. The cells were treated with PEPD (1-100 nM) and analysis of cell viability, proliferation, migration, collagen biosynthesis, PEPD activity, and the expressions of EGFR, insulin-like growth factor 1 (IGF-1), and β₁-integrin receptor including downstream signaling proteins were performed. It has been found that PEPD stimulated proliferation and migration of fibroblasts via activation of the EGFR-downstream PI3K/Akt/mTOR signaling pathway. Simultaneously, PEPD stimulated the expression of β₁-integrin and IGF-1 receptors and proteins downstream to these receptors such as FAK, Grb2, and ERK1/2. Collagen biosynthesis was increased in control and "wounded" fibroblasts under PEPD treatment. The data suggest that PEPD-induced EGFR signaling may serve as a new attempt to therapy wound healing.

PROLIDASE: A Review from Discovery to its Role in Health and Disease

Prolidase (peptidase D), encoded by the PEPD gene, is a ubiquitously expressed cytosolic metalloproteinase, the only enzyme capable of cleaving imidodipeptides containing C-terminal proline or hydroxyproline. Prolidase catalyzes the rate-limiting step during collagen recycling and is essential in protein metabolism, collagen turnover, and matrix remodeling. Prolidase, therefore plays a crucial role in several physiological processes such as wound healing, inflammation, angiogenesis, cell proliferation, and carcinogenesis. Accordingly, mutations leading to loss of prolidase catalytic activity result in prolidase deficiency a rare autosomal recessive metabolic disorder characterized by defective wound healing. In addition, alterations in prolidase enzyme activity have been documented in numerous pathological conditions, making prolidase a useful biochemical marker to measure disease severity. Furthermore, recent studies underscore the importance of a non-enzymatic role of prolidase in cell regulation and infectious disease. This review aims to provide comprehensive information on prolidase, from its discovery to its role in health and disease, while addressing the current knowledge gaps.

Prolidase Stimulates Proliferation and Migration through Activation of the PI3K/Akt/mTOR Signaling Pathway in Human Keratinocytes

Recent reports have indicated prolidase (PEPD) as a ligand of the epidermal growth factor receptor (EGFR). Since this receptor is involved in the promotion of cell proliferation, growth, and migration, we aimed to investigate whether prolidase may participate in wound healing in vitro. All experiments were performed in prolidase-treated human keratinocytes assessing cell vitality, proliferation, and migration. The expression of downstream signaling proteins induced by EGFR, insulin-like growth factor 1 (IGF-1), transforming growth factor β₁ (TGF-β₁), and β₁-integrin receptors were evaluated by Western immunoblotting and immunocytochemical staining. To determine collagen biosynthesis and prolidase activity radiometric and colorimetric methods were used, respectively. Proline content was determined by applying the liquid chromatography coupled with mass spectrometry. We found that prolidase promoted the proliferation and migration of keratinocytes through stimulation of EGFR-downstream signaling pathways in which the PI3K/Akt/mTOR axis was involved. Moreover, PEPD upregulated the expression of β₁-integrin and IGF-1 receptors and their downstream proteins. Proline concentration and collagen biosynthesis were increased in HaCaT cells under prolidase treatment. Since extracellular prolidase as a ligand of EGFR induced cell growth, migration, and collagen biosynthesis in keratinocytes, it may represent a potential therapeutic approach for the treatment of skin wounds.

Enzymatic Degradation of Organophosphorus Pesticides and Nerve Agents by EC: 3.1.8.2

The organophosphorus substances, including pesticides and nerve agents (NAs), represent highly toxic compounds. Standard decontamination procedures place a heavy burden on the environment. Given their continued utilization or existence, considerable efforts are being made to develop environmentally friendly methods of decontamination and medical countermeasures against their intoxication. Enzymes can offer both environmental and medical applications. One of the most promising enzymes cleaving organophosphorus compounds is the enzyme with enzyme commission number (EC): 3.1.8.2, called diisopropyl fluorophosphatase (DFPase) or organophosphorus acid anhydrolase from Loligo Vulgaris or Alteromonas sp. JD6.5, respectively. Structure, mechanisms of action and substrate profiles are described for both enzymes. Wild-type (WT) enzymes have a catalytic activity against organophosphorus compounds, including G-type nerve agents. Their stereochemical preference aims their activity towards less toxic enantiomers of the chiral phosphorus center found in most chemical warfare agents. Site-direct mutagenesis has systematically improved the active site of the enzyme. These efforts have resulted in the improvement of catalytic activity and have led to the identification of variants that are more effective at detoxifying both G-type and V-type nerve agents. Some of these variants have become part of commercially available decontamination mixtures.

Recent Progress in Enzymatic Release of Peptides in Foods of Animal Origin and Assessment of Bioactivity

There is a wide variety of peptides released from food proteins that are able to exert a relevant benefit for human health, such as angiotensin-converting enzyme inhibition, antioxidant, anti-inflammatory, hypoglucemic, or antithrombotic activity, among others. This manuscript is reviewing the recent advances on enzymatic mechanisms for the hydrolysis of proteins from foods of animal origin, including the types of enzymes and mechanisms of action involved, the strategies followed for the isolation and identification of bioactive peptides through advanced proteomic tools, and the assessment of bioactivity and its beneficial effects. Specific applications in fermented and/or ripened foods where a significant number of bioactive peptides have been reported with relevant in vivo physiological effects on laboratory rats and humans as well as the hydrolysis of animal food proteins for the production of bioactive peptides are also reviewed.

Prolidase - A protein with many faces

Prolidase is a metal-dependent peptidase specialized in the cleavage of dipeptides containing proline or hydroxyproline on their C-termini. Prolidase homologues are found in all kingdoms of life. The importance of prolidase in human health is underlined by a rare hereditary syndrome referred to as Prolidase Deficiency. A growing number of studies highlight the importance of prolidase in various other human conditions, including cancer. Some recent studies link prolidase's activity-independent regulatory role to tumorigenesis. Furthermore, the enzyme or engineered variants have some applications in biotechnology. In this short review, we aim to highlight different aspects of the protein the importance of which is increasingly recognized over the last years.

Current Understanding of the Emerging Role of Prolidase in Cellular Metabolism

Prolidase [EC 3.4.13.9], known as PEPD, cleaves di- and tripeptides containing carboxyl-terminal proline or hydroxyproline. For decades, prolidase has been thoroughly investigated, and several mechanisms regulating its activity are known, including the activation of the β₁-integrin receptor, insulin-like growth factor 1 receptor (IGF-1) receptor, and transforming growth factor (TGF)-β₁ receptor. This process may result in increased availability of proline in the mitochondrial proline cycle, thus making proline serve as a substrate for the resynthesis of collagen, an intracellular signaling molecule. However, as a ligand, PEPD can bind directly to the epidermal growth factor receptor (EGFR, epidermal growth factor receptor 2 (HER2)) and regulate cellular metabolism. Recent reports have indicated that PEPD protects p53 from uncontrolled p53 subcellular activation and its translocation between cellular compartments. PEPD also participates in the maturation of the interferon α/β receptor by regulating its expression. In addition to the biological effects, prolidase demonstrates clinical significance reflected in the disease known as prolidase deficiency. It is also known that prolidase activity is affected in collagen metabolism disorders, metabolic, and oncological conditions. In this article, we review the latest knowledge about prolidase and highlight its biological function, and thus provide an in-depth understanding of prolidase as a dipeptidase and protein regulating the function of key biomolecules in cellular metabolism.

Clinical Genetics of Prolidase Deficiency: An Updated Review

Prolidase is a ubiquitous enzyme that plays a major role in the metabolism of proline-rich proteins. Prolidase deficiency is a rare autosomal recessive inborn metabolic and multisystemic disease, characterized by a protean association of symptoms, namely intellectual disability, recurrent infections, splenomegaly, skin lesions, auto-immune disorders and cytopenia. To our knowledge, no published review has assembled the different clinical data and research studies over prolidase deficiency. The aim of this study is to summarize the actual state of the art from the descriptions of all the patients with a molecular diagnosis of prolidase deficiency reported to date regarding the clinical, biological, histopathological features, therapeutic options and functional studies.

Prolidase deficiency in two dermatological patients in western Sicily

Prolidase deficiency is a rare disorder inherited through an autosomal recessive gene. The hallmark of the disorder are iminodipeptiduria, chronic skin ulcers, recurring infections, mental retardation and characteristic facial appearance, although prolidase deficiency can occur with no clinical manifestation. The primary biological function of the enzyme involves the metabolism of collagen degradation products and the recycling of proline for collagen resynthesis. We describe two patients with prolidase deficiency and review the different clinical manifestations suggesting the pathogenetic mechanism through few hypotheses.

Deiminated proteins and extracellular vesicles - Novel serum biomarkers in whales and orca

Peptidylarginine deiminases (PADs) are a family of phylogenetically conserved calcium-dependent enzymes which cause post-translational protein deimination. This can result in neoepitope generation, affect gene regulation and allow for protein moonlighting via functional and structural changes in target proteins. Extracellular vesicles (EVs) carry cargo proteins and genetic material and are released from cells as part of cellular communication. EVs are found in most body fluids where they can be useful biomarkers for assessment of health status. Here, serum-derived EVs were profiled, and post-translationally deiminated proteins and EV-related microRNAs are described in 5 ceataceans: minke whale, fin whale, humpback whale, Cuvier's beaked whale and orca. EV-serum profiles were assessed by transmission electron microscopy and nanoparticle tracking analysis. EV profiles varied between the 5 species and were identified to contain deiminated proteins and selected key inflammatory and metabolic microRNAs. A range of proteins, critical for immune responses and metabolism were identified to be deiminated in cetacean sera, with some shared KEGG pathways of deiminated proteins relating to immunity and physiology, while some KEGG pathways were species-specific. This is the first study to characterise and profile EVs and to report deiminated proteins and putative effects of protein-protein interaction networks via such post-translationald deimination in cetaceans, revealing key immune and metabolic factors to undergo this post-translational modification. Deiminated proteins and EVs profiles may possibly be developed as new biomarkers for assessing health status of sea mammals.

Deiminated proteins in extracellular vesicles and serum of llama (Lama glama)-Novel insights into camelid immunity

Peptidylarginine deiminases (PADs) are phylogenetically conserved calcium-dependent enzymes which post-translationally convert arginine into citrulline in target proteins in an irreversible manner, causing functional and structural changes in target proteins. Protein deimination causes generation of neo-epitopes, affects gene regulation and also allows for protein moonlighting. Furthermore, PADs have been found to be a phylogenetically conserved regulator for extracellular vesicle (EVs) release. EVs are found in most body fluids and participate in cellular communication via transfer of cargo proteins and genetic material. In this study, post-translationally deiminated proteins in serum and serum-EVs are described for the first time in camelids, using the llama (Lama glama L. 1758) as a model animal. We report a poly-dispersed population of llama serum EVs, positive for phylogenetically conserved EV-specific markers and characterised by TEM. In serum, 103 deiminated proteins were overall identified, including key immune and metabolic mediators including complement components, immunoglobulin-based nanobodies, adiponectin and heat shock proteins. In serum, 60 deiminated proteins were identified that were not in EVs, and 25 deiminated proteins were found to be unique to EVs, with 43 shared deiminated protein hits between both serum and EVs. Deiminated histone H3, a marker of neutrophil extracellular trap formation, was also detected in llama serum. PAD homologues were identified in llama serum by Western blotting, via cross reaction with human PAD antibodies, and detected at an expected 70 kDa size. This is the first report of deiminated proteins in serum and EVs of a camelid species, highlighting a hitherto unrecognized post-translational modification in key immune and metabolic proteins in camelids, which may be translatable to and inform a range of human metabolic and inflammatory pathologies.

Diminished Prolinemia in Chronic Chagasic Patients: A New Clue for Disease Pathology?

Trypanosoma cruzi, the etiological agent of Chagas disease, is dependent on proline for a variety of processes, such as energy metabolism, host cell invasion, differentiation, and resistance to osmotic, metabolic, and oxidative stress. On this basis, we investigated a possible relationship between prolinemia and severity of T. cruzi infection in chronic patients, as reported here. The study population consisted of 112 subjects, separated into 83 chronically T. cruzi-infected patients and 29 age-matched healthy volunteers (control) of both sexes, recruited at the Chagas Disease Service from the Department of Cardiology, Hospital Provincial del Centenario de Rosario (Rosario, Argentina). Chagasic patients were separated into three groups: chronic asymptomatic, mild/moderate, and severe chronic chagasic cardiomyopathy (CCC) subjects. We observed a significant decrease of 11.7% in prolinemia in chagasic patients when compared to controls. Further analysis within the three groups of chagasic patients also revealed a statistically significant decrease of prolinemia in severe CCC patients compared to controls, showing a relative difference of 13.6% in proline concentrations. These data point to the possibility that collagen—which participates in the healing process of cardiac tissue—and proline metabolism in the myocardium could constitute new factors affecting the evolution of Chagas disease.

Affinity Immobilization of a Bacterial Prolidase onto Metal-Ion-Chelated Magnetic Nanoparticles for the Hydrolysis of Organophosphorus Compounds

In this study, silica-coated magnetic nanoparticles (SiMNPs) with isocyanatopropyltriethoxysilane as a metal-chelating ligand were prepared for the immobilization of His6-tagged Escherichia coli prolidase (His6-EcPepQ). Under one-hour coupling, the enzyme-loading capacity for the Ni2+-functionalized SiMNPs (NiNTASiMNPs) was 1.5 mg/mg support, corresponding to about 58.6% recovery of the initial activity. Native and enzyme-bound NiNTASiMNPs were subsequently characterized by transmission electron microscopy (TEM), superparamagnetic analysis, X-ray diffraction, and Fourier transform infrared (FTIR) spectroscopy. As compared to free enzyme, His6-EcPepQ@NiNTASiMNPs had significantly higher activity at 70 °C and pH ranges of 5.5 to 10, and exhibited a greater stability during a storage period of 60 days and could be recycled 20 times with approximately 80% retention of the initial activity. The immobilized enzyme was further applied in the hydrolysis of two different organophosphorus compounds, dimethyl p-nitrophenyl phosphate (methyl paraoxon) and diethyl p-nitrophenyl phosphate (ethyl paraoxon). The experimental results showed that methyl paraoxon was a preferred substrate for His6-EcPepQ and the kinetic behavior of free and immobilized enzymes towards this substance was obviously different. Taken together, the immobilization strategy surely provides an efficient means to deposit active enzymes onto NiNTASiMNPs for His6-EcPepQ-mediated biocatalysis.

Formation of Unstable and very Reactive Chemical Species Catalyzed by Metalloenzymes: A Mechanistic Overview

Nature has tailored a wide range of metalloenzymes that play a vast array of functions in all living organisms and from which their survival and evolution depends on. These enzymes catalyze some of the most important biological processes in nature, such as photosynthesis, respiration, water oxidation, molecular oxygen reduction, and nitrogen fixation. They are also among the most proficient catalysts in terms of their activity, selectivity, and ability to operate at mild conditions of temperature, pH, and pressure. In the absence of these enzymes, these reactions would proceed very slowly, if at all, suggesting that these enzymes made the way for the emergence of life as we know today. In this review, the structure and catalytic mechanism of a selection of diverse metalloenzymes that are involved in the production of highly reactive and unstable species, such as hydroxide anions, hydrides, radical species, and superoxide molecules are analyzed. The formation of such reaction intermediates is very difficult to occur under biological conditions and only a rationalized selection of a particular metal ion, coordinated to a very specific group of ligands, and immersed in specific proteins allows these reactions to proceed. Interestingly, different metal coordination spheres can be used to produce the same reactive and unstable species, although through a different chemistry. A selection of hand-picked examples of different metalloenzymes illustrating this diversity is provided and the participation of different metal ions in similar reactions (but involving different mechanism) is discussed.

High-level expression and molecular characterization of a recombinant prolidase from Escherichia coli NovaBlue

Long-term use of organophosphorus (OP) compounds has become an increasing global problem and a major threat to sustainability and human health. Prolidase is a proline-specific metallopeptidase that can offer an efficient option for the degradation of OP compounds. In this study, a full-length gene from Escherichia coli NovaBlue encoding a prolidase (EcPepQ) was amplified and cloned into the commercially-available vector pQE-30 to yield pQE-EcPepQ. The overexpressed enzyme was purified from the cell-free extract of isopropyl thio-β-D-galactoside IPTG-induced E. coli M15 (pQE-EcPepQ) cells by nickel-chelate chromatography. The molecular mass of EcPepQ was determined to be about 57 kDa by 12% sodium dodecyl sulfate–polyacrylamide gel electrophoresis and the result of size-exclusion chromatography demonstrated that the enzyme was mainly present in 25 mM Tris–HCl buffer (pH 8.0) as a dimeric form. The optimal conditions for EcPepQ activity were 60 °C, pH 8.0, and 0.1 mM Mn²⁺ ion. Kinetic analysis with Ala-Pro as the substrate showed that the K_m and k_cat values of EcPepQ were 8.8 mM and 926.5 ± 2.0 s⁻¹, respectively. The thermal unfolding of EcPepQ followed a two-state process with one well-defined unfolding transition of 64.2 °C. Analysis of guanidine hydrochloride (GdnHCl)-induced denaturation by tryptophan emission fluorescence spectroscopy revealed that the enzyme had a [GdnHCl]_0.5,N-U value of 1.98 M. The purified enzyme also exhibited some degree of tolerance to various water/organic co-solvents. Isopropanol and tetrahydrofuran were very detrimental to the enzymatic activity of EcPepQ; however, other more hydrophilic co-solvents, such as formamide, methanol, and ethylene glycol, were better tolerated. Eventually, the non-negative influence of some co-solvents on both catalytic activity and structural stability of EcPepQ allows to adjust the reaction conditions more suitable for EcPepQ-catalyzed bioprocess.

Plasma prolidase levels as a biomarker for polycystic ovary syndrome

Aim: Assessment of plasma prolidase levels in polycystic ovary syndrome (PCOS). Patients & methods: PCOS patients were screened according to Rotterdam Criterion and prolidase levels were measured. Results: A total of 170 patients and 160 controls were recruited for the study and it was found that prolidase levels were significantly higher in PCOS group (991.10 ± 39.52) than control (621.89 ± 23.94). Furthermore it has been found that prolidase levels increase with the number of cysts in ovaries. Conclusion: Significant difference between prolidase levels in PCOS and control shows that it may be used as a diagnostic marker for disease. In addition to this, there is a positive correlation found between prolidase levels and number of cysts, hence may be used as a prognostic marker to monitor disease status.

Global Metabolic Profiling Identifies a Pivotal Role of Proline and Hydroxyproline Metabolism in Supporting Hypoxic Response in Hepatocellular Carcinoma

Purpose: Metabolic reprogramming is frequently identified in hepatocellular carcinoma (HCC), which is the most common type of liver malignancy. The reprogrammed cellular metabolisms promote tumor cell survival, proliferation, angiogenesis, and metastasis. However, the mechanisms of this process remain unclear in HCC.Experimental Design: The global nontargeted metabolic study in 69 paired hepatic carcinomas and adjacent tissue specimens was performed using capillary electrophoresis-time of flight mass spectrometry-based approach. Key findings were validated by targeted metabolomic approach. Biological studies were also performed to investigate the role of proline biosynthesis in HCC pathogenesis.Results: Proline metabolism was markedly changed in HCC tumor tissue, characterized with accelerated consumption of proline and accumulation of hydroxyproline, which significantly correlated with α-fetoprotein levels and poor prognosis in HCC. In addition, we found that hydroxyproline promoted hypoxia- and HIF-dependent phenotype in HCC. Moreover, we demonstrated that hypoxia activated proline biosynthesis via upregulation of ALDH18A1, subsequently leading to accumulation of hydroxyproline via attenuated PRODH2 activity. More importantly, we showed that glutamine, proline, and hydroxyproline metabolic axis supported HCC cell survival through modulating HIF1α stability in response to hypoxia. Finally, inhibition of proline biosynthesis significantly enhanced cytotoxicity of sorafenib in vitro and in vivoConclusions: Our results demonstrate that hypoxic microenvironment activates proline metabolism, resulting in accumulation of hydroxyproline that promotes HCC tumor progression and sorafenib resistance through modulating HIF1α. These findings provide the proof of concept for targeting proline metabolism as a potential therapeutic strategy for HCC. Clin Cancer Res; 24(2); 474-85. ©2017 AACR.

PEPD is a pivotal regulator of p53 tumor suppressor

p53 tumor suppressor responds to various cellular stresses and regulates cell fate. Here, we show that peptidase D (PEPD) binds and suppresses over half of nuclear and cytoplasmic p53 under normal conditions, independent of its enzymatic activity. Eliminating PEPD causes cell death and tumor regression due to p53 activation. PEPD binds to the proline-rich domain in p53, which inhibits phosphorylation of nuclear p53 and MDM2-mediated mitochondrial translocation of nuclear and cytoplasmic p53. However, the PEPD-p53 complex is critical for p53 response to stress, as stress signals doxorubicin and H₂O₂ each must free p53 from PEPD in order to achieve robust p53 activation, which is mediated by reactive oxygen species. Thus, PEPD stores p53 for the stress response, but this also renders cells dependent on PEPD for survival, as it suppresses p53. This finding provides further understanding of p53 regulation and may have significant implications for the treatment of cancer and other diseases.

p53 is a pivotal tumour suppressor that is activated by various cellular stress inducers. Here, the authors show that peptidase D (PEPD) promotes the growth of cancer cells by suppressing p53 and that the complex PEPD-p53 is critical for robust p53 activation in response to stress signals.

Generation of bioactive peptides during food processing

Large amounts of peptides are naturally generated in foods through the proteolysis phenomena taking place during processing. Such proteolysis is carried out either by endogenous enzymes in ripened foods or by the combined action of endogenous and microbial enzymes when fermented. Food proteins can also be isolated and hydrolysed by peptidases to produce hydrolysates. endo-peptidases act first followed by the successive action of exo-peptidases (mainly, tri- and di-peptidylpeptidases, aminopeptidases and carboxypeptidases). The generated peptides may be further hydrolysed through the gastrointestinal digestion resulting in a pool of peptides with different sequences and lengths, some of them with relevant bioactivity. However, these peptides should be absorbed intact through the intestinal barrier and reach the blood stream to exert their physiological action. This manuscript is reporting the enzymatic routes and strategies followed for the generation of bioactive peptides.

Serum Prolidase Activity as a Biomarker for Choroid Plexus Calcification

The choroid plexus (CP) performs multiple functions such as secretion and reabsorption. CP also acts as the blood-cerebrospinal fluid barrier. Prolidase plays an important role in collagen metabolism by degrading imidodipeptides, in which proline or hydroxyproline residue is located at the C-terminal end. Serum prolidase activity (SPA) may reflect the degree of fibrosis and inflammation. Choroid plexus calcification (CPC) is considered as the physiological calcification of the brain, and CPC is diagnosed by the presence of calcification in the anatomical region on computed tomography (CT). Here, CPC and non-calcified CP were defined by Hounsfield Units (HU) values of > 150 and < 50, respectively. We aimed to measure SPA in subjects with CPC and those with non-calcified CP. This study included 89 subjects who were admitted to the neurology clinic and underwent CT: 44 subjects with CPC and 45 subjects with non-calcified CP. The neurological examination of all subjects was normal; namely, the subjects with CPC were asymptomatic. The SPA level was significantly higher in the CPC group than that in the non-calcified CP group (p < 0.002), and there was a significant positive correlation between vitamin D and SPA levels in the CPC group. In contrast, the vitamin D and parathyroid hormone levels were higher in the CPC group, but the difference was not statically significant (p > 0.05). These findings indicate that SPA is a biomarker for CPC that may be predictive of future brain disease.