Proline specific peptidases

Characterization of a multimeric, eukaryotic prolyl aminopeptidase: an inducible and highly specific intracellular peptidase from the non-pathogenic fungus Talaromyces emersonii

Fungi are capable of degrading proteins in their environment by secreting peptidases. However, the link between extracellular digestion and intracellular proteolysis has scarcely been investigated. Mycelial lysates of the filamentous fungus Talaromyces emersonii were screened for intracellular peptidase production. Five distinct proteolytic activities with specificity for the p-nitroanilide (pNA) peptides Suc-AAPF-pNA, Suc-AAA-pNA, K-pNA, F-pNA and P-pNA were identified. The native enzyme responsible for the removal of N-terminal proline residues was purified to homogeneity by ammonium sulfate fractionation followed by five successive chromatographic steps. The enzyme, termed Talaromyces emersonii prolyl aminopeptidase (TePAP), displayed a 50-fold specificity for cleaving N-terminal Pro-X (k(cat)/K(m)=2.1 x 10(6) M(-1) s(-1)) compared with Ala-X or Val-X bonds. This intracellular aminopeptidase was optimally active at pH 7.4 and 50 degrees C. Peptide sequencing facilitated the design of degenerate oligonucleotides from homologous sequences encoding putative fungal proline aminopeptidases, enabling subsequent cloning of the gene. TePAP was shown to be relatively uninhibited by classical serine peptidase inhibitors and to be sensitive to selected cysteine- and histidine-modifying reagents, yet gene sequence analysis identified the protein as a serine peptidase with an alpha/beta hydrolase fold. Northern analysis indicated that Tepap mRNA levels were regulated by the composition of the growth medium. Highest Tepap transcript levels were observed when the fungus was grown in medium containing glucose and the protein hydrolysate casitone. Interestingly, both the induction profile and substrate preference of this enzyme suggest potential co-operativity between extracellular and intracellular proteolysis in this organism. Gel filtration chromatography suggested that the enzyme exists as a 270 kDa homo-hexamer, whereas most bacterial prolyl aminopeptidases (PAPs) are monomers. Phylogenetic analysis of known PAPs revealed two diverse subfamilies that are distinguishable on the basis of primary and secondary structure and appear to correlate with the subunit composition of the native enzymes. Sequence comparisons revealed that PAPs with key conserved topological features are widespread in bacterial and fungal kingdoms, and this study identified many putative PAP candidates within sequenced genomes. This work represents, to our knowledge, the first detailed biochemical and molecular analysis of an inducible PAP from a eukaryote and the first intracellular peptidase isolated from the thermophilic fungus T. emersonii.

Characterization of two proline dipeptidases (prolidases) from the hyperthermophilic archaeon Pyrococcus horikoshii

Prolidases hydrolyze the unique bond between X-Pro dipeptides and can also cleave the P-F and P-O bonds found in organophosphorus compounds, including the nerve agents, soman and sarin. The advantages of using hyperthermophilic enzymes in biodetoxification strategies are based on their enzyme stability and efficiency. Therefore, it is advantageous to examine new thermostable prolidases for potential use in biotechnological applications. Two thermostable prolidase homologs, PH1149 and PH0974, were identified in the genome of Pyrococcus horikoshii based on their sequences having conserved metal binding and catalytic amino acid residues that are present in other known prolidases, such as the previously characterized Pyrococcus furiosus prolidase. These P. horikoshii prolidases were expressed recombinantly in the Escherichia coli strain BL21 (lambdaDE3), and both were shown to function as proline dipeptidases. Biochemical characterization of these prolidases shows they have higher catalytic activities over a broader pH range, higher affinity for metal and are more stable compared to P. furiosus prolidase. This study has important implications for the potential use of these enzymes in biotechnological applications and provides further information on the functional traits of hyperthermophilic proteins, specifically metalloenzymes.

Biotechnological applications of recombinant microbial prolidases

Prolidase is a metallopeptidase that is ubiquitous in nature and has been isolated from mammals, bacteria and archaea. Prolidase specifically hydrolyzes dipeptides with a prolyl residue in the carboxy terminus (NH(2)-X-/-Pro-COOH). Currently, the only solved structure of prolidase is from the hyperthermophilic archaeon Pyrococcus furiosus. This enzyme is of particular interest because it can be used in many biotechnological applications. Prolidase is able to degrade toxic organophosphorus (OP) compounds, namely, by cleaving the P-F and P-O bonds in the nerve agents, sarin and soman. Applications using prolidase to detoxify OP nerve agents include its incorporation into fire-fighting foams and as biosensors for OP compound detection. Prolidases are also employed in the cheese-ripening process to improve cheese taste and texture. In humans, prolidase deficiency (PD) is a rare autosomal recessive disorder that affects the connective tissue. Symptoms of PD include skin lesions, mental retardation and recurrent respiratory infections. Enzyme replacement therapies are currently being studied in an effort to optimize enzyme delivery and stability for this application. Previously, prolidase has been linked to collagen metabolism and more recently is being associated with melanoma. Increased prolidase activity in melanoma cell lines has lead investigators to create cancer prodrugs targeting this enzyme. Thus, there are many biotechnological applications using recombinant and native forms of prolidase and this review will describe the biochemical and structural properties of prolidases as well as discuss their most current applications.

Processing of the phalloidin proprotein by prolyl oligopeptidase from the mushroom Conocybe albipes

The peptide toxins of poisonous Amanita mushrooms are bicyclic octapeptides (amatoxins) or heptapeptides (phallotoxins). In Amanita bisporigera, alpha-amanitin and phallacidin are synthesized as 35- and 34-amino acid proproteins, respectively, in which the amino acid sequences found in the mature toxins are flanked by conserved amino acid sequences. The presence of invariant Pro residues immediately upstream of the toxin regions and as the last predicted amino acid in the toxin regions themselves suggests that a Pro-specific peptidase is responsible for the initial post-translational processing of the Amanita toxin proproteins. We purified an enzyme from the phalloidin-producing mushroom Conocybe albipes that cleaves a synthetic 22-mer phalloidin peptide to release the mature toxin peptide (AWLATCP). Mass spectrometric analysis of the purified protein combined with isolation and sequencing of the encoding gene indicates that the responsible processing enzyme is a member of the prolyl oligopeptidase (POP) subfamily of proteases (EC 3.4.21.26). The processing enzyme was able to use the chromogenic POP substrate benzyloxycarbonyl-Gly-Pro-p-nitroanilide and was inhibited by the specific POP inhibitor benzyloxycarbonyl-Pro-prolinal. Both Pro bonds in the proprotein are cleaved by the same enzyme, with the C-terminal Pro bond cleaved first or much faster than the N-terminal Pro bond. Transient accumulation of the N-terminal intermediate indicates that cleavage is not strongly processive. A synthetic peptide representing the phallacidin proprotein was also cleaved by the POP of C. albipes, but a precursor of amanitin (which is not made by C. albipes) was cleaved inefficiently.

Evidence for catalytic roles for Plasmodium falciparum aminopeptidase P in the food vacuole and cytosol

The metalloenzyme aminopeptidase P catalyzes the hydrolysis of amino acids from the amino termini of peptides with a prolyl residue in the second position. The human malaria parasite Plasmodium falciparum expresses a homolog of aminopeptidase P during its asexual intraerythrocytic cycle. P. falciparum aminopeptidase P (PfAPP) shares with mammalian cytosolic aminopeptidase P a three-domain, homodimeric organization and is most active with Mn(II) as the cofactor. A distinguishing feature of PfAPP is a 120-amino acid amino-terminal extension that appears to be removed from the mature protein. PfAPP is present in the food vacuole and cytosol of the parasite, a distribution that suggests roles in vacuolar hemoglobin catabolism and cytosolic peptide turnover. To evaluate the plausibility of these putative functions, the stability and kinetic properties of recombinant PfAPP were evaluated at the acidic pH of the food vacuole and at the near-neutral pH of the cytosol. PfAPP exhibited high stability at 37 degrees C in the pH range 5.0-7.5. In contrast, recombinant human cytosolic APP1 was unstable and formed a high molecular weight aggregate at acidic pH. At both acidic and slightly basic pH values, PfAPP efficiently hydrolyzed the amino-terminal X-Pro bond of the nonapeptide bradykinin and of two globin pentapeptides that are potential in vivo substrates. These results provide support for roles for PfAPP in peptide catabolism in both the food vacuole and the cytosol and suggest that PfAPP has evolved a dual distribution in response to the metabolic needs of the intraerythrocytic parasite.

In vivo multiplex quantitative analysis of 3 forms of alpha melanocyte stimulating hormone in pituitary of prolyl endopeptidase deficient mice

Background

In vitro reactions are useful to identify putative enzyme substrates, but in vivo validation is required to identify actual enzyme substrates that have biological meaning. To investigate in vivo effects of prolyl endopeptidase (PREP), a serine protease, on alpha melanocyte stimulating hormone (α-MSH), we developed a new mass spectrometry based technique to quantitate, in multiplex, the various forms of α-MSH.

Methods

Using Multiple Reaction Monitoring (MRM), we analyzed peptide transitions to quantify three different forms of α-MSH. Transitions were first confirmed using standard peptides. Samples were then analyzed by mass spectrometry using a triple quadrupole mass spectrometer, after elution from a reverse phase C18 column by a gradient of acetonitrile.

Results

We first demonstrate in vitro that PREP digests biological active alpha melanocyte stimulating hormone (α-MSH_1–13), by cleaving the terminal amidated valine and releasing a truncated alpha melanocyte stimulating hormone (α-MSH_1–12) product – the 12 residues α-MSH form. We then use the technique in vivo to analyze the MRM transitions of the three different forms of α-MSH: the deacetylated α-MSH_1–13, the acetylated α-MSH_1–13 and the truncated form α-MSH_1–12. For this experiment, we used a mouse model (PREP-GT) in which the serine protease, prolyl endopeptidase, is deficient due to a genetrap insertion. Here we report that the ratio between acetylated α-MSH_1–13 and α-MSH_1–12 is significantly increased (P-value = 0.015, N = 6) in the pituitaries of PREP-GT mice when compared to wild type littermates. In addition no significant changes were revealed in the relative level of α-MSH_1–13 versus the deacetylated α-MSH_1–13. These results combined with the demonstration that PREP digests α-MSH_1–13 in vitro, strongly suggest that α-MSH_1–13 is an in vivo substrate of PREP.

Conclusion

The multiplex targeted quantitative peptidomics technique we present in this study will be decidedly useful to monitor several neuropeptide enzymatic reactions in vivo under varying conditions.

Issues about the physiological functions of prolyl oligopeptidase based on its discordant spatial association with substrates and inconsistencies among mRNA, protein levels, and enzymatic activity

Prolyl oligopeptidase (POP) is a serine endopeptidase that hydrolyses proline-containing peptides shorter than 30 amino acids. POP may be associated with cognitive functions, possibly via the cleavage of neuropeptides. Recent studies have also suggested novel non-hydrolytic and non-catalytic functions for POP. Moreover, POP has also been proposed as a regulator of inositol 1,4,5-triphosphate signaling and several other functions such as cell proliferation and differentiation, as well as signal transduction in the central nervous system, and it is suspected to be involved in pathological conditions such as Parkinson's and Alzheimer's diseases and cancer. POP inhibitors have been developed to restore the depleted neuropeptide levels encountered in aging or in neurodegenerative disorders. These compounds have shown some antiamnesic effects in animal models. However, the mechanisms of these hypothesized actions are still far from clear. Moreover, the physiological role of POP has remained unknown, and a lack of basic studies, including its distribution, is obvious. The aim of this review is to gather information about POP and to propose some novel roles for this enzyme based on its distribution and its discordant spatial association with its best known substrates.

Attacking the multi-tiered proteolytic pathology of COPD: new insights from basic and translational studies

Protease activity in inflammation is complex. Proteases released by cells in response to infection, cytokines, or environmental triggers like cigarette smoking cause breakdown of the extracellular matrix (ECM). In chronic inflammatory diseases like chronic obstructive pulmonary disease (COPD), current findings indicate that pathology and morbidity are driven by dysregulation of protease activity, either through hyperactivity of proteases or deficiency or dysfunction their antiprotease regulators. Animal studies demonstrate the accuracy of this hypothesis through genetic and pharmacologic tools. New work shows that ECM destruction generates peptide fragments active on leukocytes via neutrophil or macrophage chemotaxis towards collagen and elastin derived peptides respectively. Such fragments now have been isolated and characterized in vivo in each case. Collectively, this describes a biochemical circuit in which protease activity leads to activation of local immunocytes, which in turn release cytokines and more proteases, leading to further leukocyte infiltration and cyclical disease progression that is chronic. This circuit concept is well known, and is intrinsic to the protease-antiprotease hypothesis; recently analytic techniques have become sensitive enough to establish fundamental mechanisms of this hypothesis, and basic and clinical data now implicate protease activity and peptide signaling as pathologically significant pharmacologic targets. This review discusses targeting protease activity for chronic inflammatory disease with special attention to COPD, covering important basic and clinical findings in the field; novel therapeutic strategies in animal or human studies; and a perspective on the successes and failures of agents with a focus on clinical potential in human disease.

Enzymatic degradation of endomorphins

Centrally acting plant opiates, such as morphine, are the most frequently used analgesics for the relief of severe pain, even though their undesired side effects are serious limitation to their usefulness. The search for new therapeutics that could replace morphine has been mainly focused on the development of peptide analogs or peptidomimetics with high selectivity for one receptor type and high bioavailability, that is good blood-brain barrier permeability and enzymatic stability. Drugs, in order to be effective, must be able to reach the target tissue and to remain metabolically stable to produce the desired effects. The study of naturally occurring peptides provides a rational and powerful approach in the design of peptide therapeutics. Endogenous opioid peptides, endomorphin-1 and endomorphin-2, are two potent and highly selective mu-opioid receptor agonists, discovered only a decade ago, which display potent analgesic activity. However, extensive studies on the possible use of endomorphins as analgesics instead of morphine met with failure due to their instability. This review deals with the recent investigations that allowed determine degradation pathways of endomorphins in vitro and in vivo and propose modifications that will lead to more stable analogs.

A possible role of prolyl oligopeptidase during Linum usitatissimum (flax) seed development

Involvement of prolyl oligopeptidases (POPs) in the control of several mammalian peptide hormone signalling pathways has been studied extensively in recent years. POPs are ubiquitous enzymes, but little attention has been paid to understanding their function in plants. Using a cDNA-AFLP approach, two flax (Linum usitatissimum) POP ESTs were identified as being specifically expressed in the early stages of flax seed development. This specific expression was confirmed using real time RT-PCR and in situ hybridisation approaches. Seed expression of Arabidopsis POP genes was measured and showed no specificity. Comparison between results obtained with flax and Arabidopsis is discussed in order to address a hypothetic function for POPs during seed formation. These results provide the first insights into POP gene expression and hypothetical function in plants.

Methotrexate and cyclosporine treatments modify the activities of dipeptidyl peptidase IV and prolyl oligopeptidase in murine macrophages

Analysis of the effects of cyclosporine A (25–28 mgkg⁻¹) and/or methotrexate (0.1 mgkg⁻¹) treatments on dipeptidyl peptidase IV (DPPIV) and prolyl oligopeptidase (POP) activities and on algesic response in two distinct status of murine macrophages (Mφs) was undertaken. In resident Mφs, DPPIV and POP were affected by neither individual nor combined treatments. In thioglycolate-elicited Mφs, methotrexate increased DPPIV (99–110%) and POP (60%), while cyclosporine inhibited POP (21%). Combined treatment with both drugs promoted a rise (51–84%) of both enzyme activities. Only cyclosporine decreased (42%) the tolerance to algesic stimulus. Methotrexate was revealed to exert prevalent action over that of cyclosporine on proinflammatory Mφ POP. The opposite effects of methotrexate and cyclosporine on POP activity might influence the availability of the nociceptive mediators bradykinin and substance P in proinflammatory Mφs. The exacerbated response to thermally induced algesia observed in cyclosporine-treated animals could be related to upregulation of those mediators.

Cloning, expression and characterization of insulin-degrading enzyme from tomato (Solanum lycopersicum)

A cDNA encoding insulin-degrading enzyme (IDE) was cloned from tomato (Solanum lycopersicum) and expressed in Escherichia coli in N-terminal fusion with glutathione S-transferase. GST-SlIDE was characterized as a neutral thiol-dependent metallopeptidase with insulinase activity: the recombinant enzyme cleaved the oxidized insulin B chain at eight peptide bonds, six of which are also targets of human IDE. Despite a certain preference for proline in the vicinity of the cleavage site, synthetic peptides were cleaved at apparently stochastic positions indicating that SlIDE, similar to IDEs from other organisms, does not recognize any particular amino acid motif in the primary structure of its substrates. Under steady-state conditions, an apparent K(m) of 62+/-7 microm and a catalytic efficiency (k(cat)/K(m)) of 62+/-15 mm(-1) s(-1) were determined for Abz-SKRDPPKMQTDLY(NO(3))-NH(2) as the substrate. GST-SlIDE was effectively inhibited by ATP at physiological concentrations, suggesting regulation of its activity in response to the energy status of the cell. While mammalian and plant IDEs share many of their biochemical properties, this similarity does not extend to their function in vivo, because insulin and the beta-amyloid peptide, well-established substrates of mammalian IDEs, as well as insulin-related signaling appear to be absent from plant systems.

Gene family encoding the major toxins of lethal Amanita mushrooms

Amatoxins, the lethal constituents of poisonous mushrooms in the genus Amanita, are bicyclic octapeptides. Two genes in A. bisporigera, AMA1 and PHA1, directly encode alpha-amanitin, an amatoxin, and the related bicyclic heptapeptide phallacidin, a phallotoxin, indicating that these compounds are synthesized on ribosomes and not by nonribosomal peptide synthetases. alpha-Amanitin and phallacidin are synthesized as proproteins of 35 and 34 amino acids, respectively, from which they are predicted to be cleaved by a prolyl oligopeptidase. AMA1 and PHA1 are present in other toxic species of Amanita section Phalloidae but are absent from nontoxic species in other sections. The genomes of A. bisporigera and A. phalloides contain multiple sequences related to AMA1 and PHA1. The predicted protein products of this family of genes are characterized by a hypervariable "toxin" region capable of encoding a wide variety of peptides of 7-10 amino acids flanked by conserved sequences. Our results suggest that these fungi have a broad capacity to synthesize cyclic peptides on ribosomes.

Roles for two aminopeptidases in vacuolar hemoglobin catabolism in Plasmodium falciparum

During the erythrocytic stage of its life cycle, the human malaria parasite Plasmodium falciparum catabolizes large quantities of host-cell hemoglobin in an acidic organelle, the food vacuole. A current model for the catabolism of globin-derived oligopeptides invokes peptide transport out of the food vacuole followed by hydrolysis to amino acids by cytosolic aminopeptidases. To test this model, we have examined the roles of four parasite aminopeptidases during the erythrocytic cycle. Localization of tagged aminopeptidases, coupled with biochemical analysis of enriched food vacuoles, revealed the presence of amino acid-generating pathways in the food vacuole as well as the cytosol. Based on the localization data and in vitro assays, we propose a specific role for one of the plasmodial enzymes, aminopeptidase P, in the catabolism of proline-containing peptides in both the vacuole and the cytosol. We establish an apparent requirement for three of the four aminopeptidases (including the two food vacuole enzymes) for efficient parasite proliferation. To gain insight into the impact of aminopeptidase inhibition on parasite development, we examined the effect of the presence of amino acids in the culture medium of the parasite on the toxicity of the aminopeptidase inhibitor bestatin. The ability of bestatin to block parasite replication was only slightly affected when 19 of 20 amino acids were withdrawn from the medium, indicating that exogenous amino acids cannot compensate for the loss of aminopeptidase activity. Together, these results support the development of aminopeptidase inhibitors as novel chemotherapeutics directed against malaria.

Plant phenolics as prolyl endopeptidase inhibitors

Prolyl endopeptidase (PEP, EC 3.4.21.26), a serine protease, is widely distributed in various organs, particularly in the brains of Alzheimer's disease patients. The expression of PEP in Alzheimer's patients has been found to be significantly higher than that of the normal person, suggesting that a specific PEP inhibitor can be a good candidate for an anti-amnestic drug. In the current study, thirty-nine plant phenolics were investigated to determine their roles as prolyl endopeptidase (PEP) inhibitors. Nineteen compounds such as 1,2,3-trigalloyl glucopyranoside, 1,2,6-trigalloyl glucopyranoside, 1,2,3,4,6-pentagalloyl gluco-pyranoside, 1,2,6-trigalloyl alloside, 1,3,6-trigalloyl alloside, 1,2,3,6-tetragalloyl alloside, acetonyl geraniin, corilagin, elaeocarpusin, euphorscopin, geraniin, helioscopin B, helioscopinin A, helioscopinin B, jolkinin, macranganin, rugosin E, supinanin, and teracatain exhibited strong inhibition against PEP (IC50 26.7 - 443.7 x 10(-9) M). Rugosin E (IC50 26.7 x 10(-9) M) showed the most effective inhibition followed by 1,2,6-trigalloyl glucopyranoside (IC5031.4 x 10(-9) M) and macranganin (IC5042.6 x 10(-9) M). No significant structure-activity relationship was found; however, at least, three pyrogallol groups seem to be a minimal requirement for stronger activity against PEP All 19 active compounds inhibited PEP in a non-competitive mode with a substrate in Dixon plots. They did not show significant effects against other serine proteases such as trypsin, chymotrypsin and elastase, indicating that they were relatively specific PEP inhibitors.

Human dipeptidyl peptidase III acts as a post-proline-cleaving enzyme on endomorphins

Dipeptidyl peptidase III (DPP III) is a zinc exopeptidase with an implied role in the mammalian pain-modulatory system owing to its high affinity for enkephalins and localisation in the superficial laminae of the spinal cord dorsal horn. Our study revealed that this human enzyme hydrolyses opioid peptides belonging to three new groups, endomorphins, hemorphins and exorphins. The enzymatic hydrolysis products of endomorphin-1 were separated and quantified by capillary electrophoresis and the kinetic parameters were determined for human DPP III and rat DPP IV. Both peptidases cleave endomorphin-1 at comparable rates, with liberation of the N-terminal Tyr-Pro. This is the first evidence of DPP III acting as an endomorphin-cleaving enzyme.

2(S)-(Cycloalk-1-enecarbonyl)-1-(4-phenyl-butanoyl)pyrrolidines and 2(S)-(aroyl)-1-(4-phenylbutanoyl)pyrrolidines as prolyl oligopeptidase inhibitors

In order to replace the P2-P1 amide group, different 1-cycloalkenyls and 2-aryls were studied in the place of the P1 pyrrolidine group of a 4-phenylbutanoyl-L-Pro-pyrrolidine structure, which is a well-known prolyl oligopeptidase inhibitor SUAM-1221. The 1-cyclopentenyl and the 2-thienyl groups gave novel compounds, which were equipotent with the corresponding pyrrolidine-analog SUAM-1221. It was shown that the P2-P1 amide group of POP inhibitors can be replaced by an alpha,beta-unsaturated carbonyl group or the aryl conjugated carbonyl group.

On the role of prolyl oligopeptidase in health and disease

Prolyl oligopeptidase (POP) is a serine peptidase which digests small peptide-like hormones, neuroactive peptides, and various cellular factors. Therefore, this peptidase has been implicated in many physiological processes as well as in some psychiatric disorders, most probably through interference in inositol cycle. Intense research has been performed to elucidate, on the one hand, the basic structure, ligand binding, and kinetic properties of POP, and on the other, the pharmacology of its inhibitors. There is fairly strong evidence of in vivo importance of POP on substance P, arginine vasopressin, thyroliberin and gonadoliberin metabolism. However, information about the biological relevance of POP is not yet conclusive. Evidence regarding the physiological role of POP is lacking, which is surprising considering that peptidase inhibitors have been exploited for drug development, some of which are currently in clinical trials as memory enhancers for the aged and in a variety of neurological disorders. Here we review the recent progress on POP research and evaluate the relevance of the peptidase in the metabolism of various neuropeptides. The recognition of novel forms and relatives of POP may improve our understanding of how this family of proteins functions in normal and in neuropathological conditions.

Identification of neuropeptide Y cleavage products in human blood to improve metabolic stability

Regulatory, receptor-binding peptides are considered as the agents of choice for diagnostic imaging and therapy of cancers, because their receptors are overexpressed in various human cancer cells. It has been recently indicated that there is a putative role of NPY in breast tumors. The expression of the two best-investigated NPY receptor subtypes, Y1 and Y2, in breast tissue shows predominant occurrence of the Y1 receptor subtype in tumors, whereas Y2 receptors are found in nonproliferative tissue. To investigate the usefulness of NPY analogs for tumor diagnosis and therapy, we investigated the metabolic stability of receptor-selective NPY analogs in human blood plasma. NPY analogs were synthesized by Fmoc/t-Bu solid-phase strategy. Prior to the cleavage of peptides from the resin, they were labeled with 5(6)-carboxyfluorescein (CF) either at the N-terminus or at the side chain of Lys4. For the metabolic stability study, the digestion of peptides was monitored by HPLC and the cleavage products were identified by MALDI-ToF mass spectrometry. The data showed that full-length [Phe7, Pro34]NPY analogs, which show high binding affinity to Y1 receptors are enzymatically more stable than centrally truncated analogs, which show high binding affinity to Y2 receptors. Furthermore, the N-terminally CF-labeled Y1 and Y2 receptor-selective peptides were found to be enzymatically more resistant than their counterparts containing the CF label at Lys4 side chain.

Beneficial Effect of Prolyl Oligopeptidase Inhibition on Spatial Memory in Young but Not in Old Scopolamine-Treated Rats

The effects of a novel prolyl oligopeptidase (POP) inhibitor KYP-2047 on spatial memory of young (3-month-old) and old (8- to 9-month-old) scopolamine-treated rats (0.4 mg/kg intraperitoneally) was investigated in the Morris water maze. In addition, the concentrations of promnesic neuropeptide substrates of POP, substance P and neurotensin in various brain areas after acute and chronic POP inhibition were measured in young rats. In addition, inositol-1,4,5-trisphosphate (IP(3)) levels were assayed in rat cortex and hippocampus after effective 2.5-day POP inhibition. KYP-2047 (1 or 5 mg/kg 30 min. before daily testing) dose-dependently improved the escape performance (i.e. latency to find the hidden platform and swimming path length) of the young but not the old rats in the water maze. POP inhibition had no consistent effect on substance P levels in cortex, hippocampus or hypothalamus, and only a modest increase in neurotensin concentration was observed in the hypothalamus after a single dose of KYP-2047. Moreover, IP(3) concentrations remained unaffected in cortex and hippocampus after POP inhibition. In conclusion, the behavioural data support the earlier findings of the promnesic action of POP inhibitors, but the mechanism of the memory-enhancing action remains unclear.

Molecular characterisation of six patients with prolidase deficiency: identification of the first small duplication in the prolidase gene and of a mutation generating symptomatic and asymptomatic outcomes within the same family

Prolidase deficiency (PD) is a rare autosomal recessive connective tissue disorder caused by mutations in the prolidase gene. The PD patients show a wide range of clinical outcomes characterised mainly by intractable skin ulcers, mental retardation and recurrent respiratory infections. Here we describe five different PEPD mutations in six European patients. We identified two new PEPD mutant alleles: a 13 bp duplication in exon 8, which is the first reported duplication in the prolidase gene and a point mutation resulting in a change in amino acid E412, a highly conserved residue among different species. The E412K substitution is responsible for the first reported phenotypic variability within a family with severe and asymptomatic outcomes.

Ontogeny of prolyl endopeptidase and pyroglutamyl peptidase I in rat tissues

Prolyl endopeptidase and pyroglutamyl peptidase I are enzymes which participate in the degradation of thyrotropin-releasing hormone (TRH), a hormone which is thought to play an important role in the development of organs and tissues. Here, we have characterized the ontogeny of TRH degrading enzyme activity in the brain cortex, lung, heart, kidney and liver. Overall, prolyl endopeptidase activity was found to be 2 to 5 fold higher in newborn vs. adult rat tissues, with the exception of the soluble form in the liver and the particulate form in the lung. In contrast, the developmental profile of pyroglutamyl peptidase I activity was found to be more variable and tissue dependent. These results corroborate the idea that both enzymes play important, tissue-specific roles during the development and maturation of rat organs.

Ontogeny of prolyl endopeptidase and pyroglutamyl peptidase I in rat tissues

Prolyl endopeptidase and pyroglutamyl peptidase I are enzymes which participate in the degradation of thyrotropin-releasing hormone (TRH), a hormone which is thought to play an important role in the development of organs and tissues. Here, we have characterized the ontogeny of TRH degrading enzyme activity in the brain cortex, lung, heart, kidney and liver. Overall, prolyl endopeptidase activity was found to be 2 to 5 fold higher in newborn vs. adult rat tissues, with the exception of the soluble form in the liver and the particulate form in the lung. In contrast, the developmental profile of pyroglutamyl peptidase I activity was found to be more variable and tissue dependent. These results corroborate the idea that both enzymes play important, tissue-specific roles during the development and maturation of rat organs.

Gene expression analysis of bipolar disorder reveals downregulation of the ubiquitin cycle and alterations in synaptic genes

Bipolar affective disorder is a severe psychiatric disorder with a strong genetic component but unknown pathophysiology. We used microarray technology to determine the expression of approximately 22,000 mRNA transcripts in post-mortem tissue from two brain regions in patients with bipolar disorder and matched healthy controls. Dorsolateral prefrontal cortex tissue from a cohort of 70 subjects and orbitofrontal cortex tissue from a separate cohort of 30 subjects was investigated. The final analysis included 30 bipolar and 31 control subjects for the dorsolateral prefrontal cortex and 10 bipolar and 11 control subjects for the orbitofrontal cortex. Differences between disease and control groups were identified using a rigorous statistical analysis with correction for confounding variables and multiple testing. In the orbitofrontal cortex, 393 differentially expressed transcripts were identified by microarray analysis and a representative subset was validated by quantitative real-time PCR. Pathway analysis revealed significant upregulation of genes involved in G-protein coupled receptor signalling and response to stimulus (in particular the immune response), while genes relating to the ubiquitin cycle and intracellular transport showed coordinated downregulation in bipolar disorder. Additionally, several genes involved in synaptic function were significantly downregulated in bipolar disorder. No significant changes in gene expression were observed in the dorsolateral prefrontal cortex using microarray analysis or quantitative real-time PCR. Our findings implicate the orbitofrontal cortex as a region prominently involved in bipolar disorder and indicate that diverse processes are affected. Overall, our results suggest that dysregulation of the ubiquitin pathway and synaptic function may be central to the disease process.

Catabolism of the octadecaneuropeptide ODN by prolyl endopeptidase: identification of an unusual cleavage site

The octadecaneuropeptide ODN (QATVGDVNTDRPGLLDLK), a biologically active fragment of diazepam-binding inhibitor, exerts a number of behavioral and neurophysiological activities. The presence of a proline residue in the sequence of ODN led us to investigate the role of proline endopeptidase (PEP) in the catabolism of this neuropeptide. The effect of PEP on the breakdown of ODN and related analogs was studied by combining RP-HPLC analysis and MALDI-TOF MS characterization. Incubation of ODN with PEP generated two products, i.e. ODN3-18 and ODN5-18 which resulted from cleavage of the Ala-Thr and Val-Gly peptide bonds. S 17092, a specific PEP inhibitor, significantly reduced the PEP-induced cleavages of ODN. Similarly, [Ala2]OP showed S 17092-sensitive post-alanine cleavage, while [pGlu1]ODN and OP (ODN11-18) were not catabolized by the enzyme. For all these peptides, cleavage of the Pro-Gly peptide bond by PEP was never observed, even after prolonged incubation times. In contrast, PEP hydrolyzed human urotensin II at the canonical post-proline site. Collectively, these data suggest that the Ala2 residue is the preferential cleavage site of ODN and that the Pro-Gly bond of ODN is not hydrolyzed by PEP. In addition, this study reveals for the first time that the endoproteolytic activity of PEP can specifically take place after a valine moiety.

Dipeptidyl peptidase II and leukocyte cell death

Dipeptidyl peptidase (DPP) II (E.C. 3.4.14.2) is an intracellular protease that releases, preferably at acidic pH, N-terminal dipeptides from oligopeptides with Pro or Ala in the penultimate position. The natural substrates and the physiological role of DPPII remain unclear. The aim of the present study was to investigate the involvement of DPPII activity in different forms of cell death (apoptosis, necrosis and autophagy) in human leukocytes. We determined specific DPP activities in leukocytes. Compared to other subpopulations of peripheral blood mononuclear cells (PBMC), we observed relatively high DPPII specific activity in monocytic cells, opening new perspectives for further investigation of the DPPII functions. A second intriguing finding was that DPPII specific activity increased during necrosis, whereas induction of apoptosis or autophagy did not affect any of the dipeptidyl peptidase activities. Finally, we showed that inhibition of DPPII (>90%) using the in vitro applicable, highly potent (K(i) of 0.082+/-0.048 nM) and selective DPPII inhibitor UAMC00039, did not induce any form of cell death in leukocytes. These data are of importance for a more precise interpretation of the in vitro and in vivo effects of other dipeptidyl peptidase inhibitors.

Cloning, expression, and characterization of aminopeptidase P from the hyperthermophilic archaeon Thermococcus sp. strain NA1

Genomic analysis of a hyperthermophilic archaeon, Thermococcus sp. strain NA1, revealed the presence of a 1,068-bp open reading frame encoding a protein consisting of 356 amino acids with a calculated molecular mass of 39,714 Da (GenBank accession no. DQ144132). Sequence analysis showed that it was similar to the putative aminopeptidase P (APP) of Thermococcus kodakaraensis KOD1. Amino acid residues important for catalytic activity and the metal binding ligands conserved in bacterial, nematode, insect, and mammalian APPs were also conserved in the Thermococcus sp. strain NA1 APP. The archaeal APP, designated TNA1_APP (Thermococcus sp. strain NA1 APP), was cloned and expressed in Escherichia coli. The recombinant enzyme hydrolyzed the amino-terminal Xaa-Pro bond of Lys(Nepsilon-Abz)-Pro-Pro-pNA and the dipeptide Met-Pro (Km, 0.96 mM), revealing its functional identity. Further enzyme characterization showed the enzyme to be a Co2+-, Mn2+-, or Zn2+-dependent metallopeptidase. Optimal APP activity with Met-Pro as the substrate occurred at pH 5 and a temperature of 100 degrees C. The APP was thermostable, with a half-life of >100 min at 80 degrees C. This study represents the first characterization of a hyperthermophilic archaeon APP.

Tyrosine 387 and arginine 404 are critical in the hydrolytic mechanism of Escherichia coli aminopeptidase P

Analysis of the pH-rate profile for catalysis of bradykinin cleavage by aminopeptidase P (AMPP), a manganese-containing hydrolase from Escherichia coli, was carried out to show that optimal catalytic function is obtained at neutral pH. On the basis of information derived from the crystal structure, peptidase sequence alignments, and the hydrolysis of organophosphate triesters, active site residues Arg153, Arg370, Trp88, Tyr387, and Arg404 were identified as potential catalytic residues. Site-directed mutagenesis was used to substitute these residues with Leu, Ala, Trp, Lys, or Phe. The kcat values for the Arg153, Arg370, and Trp88 mutants were nearly the same as that for the wild-type enzyme. The kcat values of the R404K, R404A, and Y387A mutants were lower by factors of 285, 400, and 16, respectively. Inductively coupled plasma mass spectrometry and circular dichroism spectroscopy showed that Arg404 is not required for metal chelation or stabilization of protein secondary structure. The hydrogen bond network observed between the side chains of conserved residues Asp260, Arg404, and Tyr387 indicated that Arg404 participates in proton relay. This was further evidenced by the return of activity in the R404A mutant by the addition of guanidine. Also, reduced catalytic efficiency in the R404K mutant, which conserves the positive charge at the bridge site, shows that only the arginine group of Arg404 (not the ammonium group of Lys404) can participate in the hydrogen bond network. The hydrogen bond interaction between the Arg404 and the Tyr387 ring hydroxyl group is suggested by the reduced catalytic efficiency of the Y387F mutant.

Proteolytic activity and reduction of gliadin-like fractions by sourdough lactobacilli

AIMS

To characterize the peptide hydrolase system of Lactobacillus plantarum CRL 759 and CRL 778 and evaluate their proteolytic activity in reducing gliadin-like fractions.

METHODS AND RESULTS

The intracellular peptide hydrolase system of Lact. plantarum CRL 759 and CRL 778 involves amino-, di- (DP), tri- (TP) and endopeptidase activities. These peptidases are metalloenzymes inhibited by EDTA and 1,10-phenanthroline and stimulated by Co2+. DP and TP activities of Lact. plantarum CRL 759 and CRL 778, respectively, were completely inhibited by Cu2+. Lactobacillus plantarum CRL 778 showed the highest proteolytic activity and amino acids release in fermented dough. The synthetic 31-43 alpha-gliadin fragment was hydrolysed to 36% and 73% by Lact. plantarum CRL 778 and CRL 759 respectively.

CONCLUSIONS

Lactobacillus plantarum CRL 759 and CRL 778 have an active proteolytic system, which is responsible for the high amino acid release during sourdough fermentation and the hydrolysis of the 31-43 alpha-gliadin-like fragment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides new information of use when obtaining sourdough starters for bread making. Moreover, knowledge regarding lactobacilli capable of reducing the level of gliadin-like fractions, a toxic peptide for coeliac patients, has a beneficial health impact.

Renal and macrophage aminopeptidase activities in cyclosporin-treated mice

Cyclosporin, an immunosuppressive drug, is known to affect macrophage and to exert a nephrotoxic effect. Aminopeptidases play important roles for renal and macrophage functions. In this work, we attempt to test the hypothesis that the aminopeptidases participate within macrophage and renal effects induced by cyclosporin. Macrophage and renal aminopeptidase activities of cyclosporin-treated and control mice were evaluated, as well as renal caspase 3 activity, hematocrit, urinary protein and plasma osmolality, creatinine and uric acid concentrations. Cyclosporin treatment increased caspase 3 activity, hematocrit and osmolality, while urinary protein, creatinine and uric acid were unaltered. Soluble and particulate aminopeptidases in resident and elicited macrophages were unaffected by cyclosporin. The treatment with cyclosporin increased neutral, basic, cystyl, prolyl imino and pyroglutamyl soluble aminopeptidase activities in the renal cortex. Acid and basic soluble aminopeptidase activities increased in the renal medulla. Increased levels of particulate form in the cortex were detected for acid and pyroglutamyl aminopeptidase activities. Cyclosporin increased cortical soluble while decreased medullar particulate prolyl dipeptidyl aminopeptidase IV activity. With the exception of prolyl dipeptidyl aminopeptidase IV, particulate aminopeptidase activities returned to levels similar to controls after fifteen days of cyclosporin withdrawal, and soluble aminopeptidase activities did not regress. Our data indicate that the adopted regimen of cyclosporin treatment produced mild renal impairment with consistent changes on the levels of renal but not macrophage aminopeptidase activities. The obtained profiles of macrophage and renal aminopeptidase activities should be considered into the elaboration of new potential strategies for preventing nephrotoxicity during the treatment with cyclosporin.

Prolyl endopeptidase inhibitory activity of unsaturated fatty acids

Prolyl endopeptidase (PEP, EC 3.4.21.26) is widely distributed in various organs, particularly in the brains of amnestic patients. Evaluation of PEP levels in postmortem brains of Alzheimer's disease patients revealed significant increases in PEP activity, suggesting that a specific PEP inhibitor can be a good candidate for an antiamnestic drug. In this study, mono- and polyunsaturated fatty acids were investigated to determine their role as PEP inhibitors. Oleic, linoleic, and arachidonic acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) showed PEP inhibitory activities (IC50 values of 23.6 +/- 0.4, 43.8 +/- 1.8, 53.4 +/- 1.2, 99.4 +/- 1.2, and 46.2 +/- 1.0 microM, respectively), indicating that they were effective PEP inhibitors, with inhibition constant (Ki) values of 26.7 +/- 0.3, 51.0 +/- 0.7, 91.3 +/- 3.1, 247.5 +/- 2.6, and 89.0 +/- 2.3 microM, respectively. Oleic acid showed the highest PEP inhibitory activity. Dixon plots of PEP inhibition showed oleic, linoleic, and arachidonic acids, EPA, and DHA are noncompetitive inhibitors; despite higher IC50 values of these unsaturated fatty acids than strong natural inhibitors, they may have potential use in preventing memory loss.

Identification of mature nocistatin and nociceptin in human brain and cerebrospinal fluid by mass spectrometry combined with affinity chromatography and HPLC

Nocistatin (NST) and nociceptin/orphanin FQ (NCP) are two important bio-peptides derived from the precursor protein prepronociceptin (ppNCP), involved in several central nervous system (CNS) functions including pain transmission. Since the actual form of human NST in CNS is not fully characterized, we studied the structure of NST from human brain tissue and cerebrospinal fluid (CSF) samples. NST and NCP were isolated from human brain and CSF samples by affinity chromatography combined with HPLC. Mass spectrometry was used for the identification and characterization of the peptides. The total NST immunoreactivity was detected as 11.5+/-2.3 pmol/g tissue for the brain and 0.44 pmol/ml for the pooled CSF sample after the HPLC purification by radioimmunoassay. The presence of two different forms of mature nocistatin (NST-17 and NST-30) and a possible N-terminal methionine cleaved NST-29 were confirmed by both radioimmunoassay and mass spectrometry. Affinity chromatography, HPLC and mass spectrometry methods used in this study were highly sensitive and suitable for identification of actual chemical structures and quantification of very small amounts of peptides in biological samples. The present findings may help further for search for new treatment of neuropathic pain, which is often poorly managed by current therapies.

Rigidity and Flexibility of Dipeptidyl Peptidase IV: Crystal Structures of and Docking Experiments with DPIV

Dipeptidyl peptidase IV (DPIV) is an alpha,beta-hydrolase-like serine exopeptidase, which removes dipeptides, preferentially with a C-terminal l-Pro residue, from the N terminus of longer peptide substrates. Previously, we determined the tetrameric 1.8A crystal structure of native porcine DPIV. Each monomer is composed of a beta-propeller and a catalytic domain, which together embrace an internal cavity housing the active centre. This cavity is connected to the bulk solvent by a "propeller opening" and a "side opening". Here, we analyse DPIV complexes with a t-butyl-Gly-Pro-Ile tripeptide, Pro-boroPro, a piperazine purine compound, and aminoethyl phenyl sulfonylfluoride. The latter two compounds bind to the active-site groove in a compact and a quite bulky manner, respectively, causing considerable shifts of the catalytic Ser630 side-chain and of the Tyr547 phenolic group, which forms the oxyanion hole. The tripeptide, mimicking a peptide substrate, is clamped to the active site through tight interactions via its N-terminal alpha-ammonium group, the P2 carbonyl group, the P1-l-Pro side-chain, the C-terminal carboxylate group, and the stable orthoacid ester amide formed between the scissile peptide carbonyl group and Ser630 O(gamma). This stable trapping of the tripeptide could be due to stabilization of the protonated His740 imidazolium cation by the adjacent negatively charged C-terminal carboxylate group, preventing proton transfer to the leaving group nitrogen atom. Docking experiments with the compact rigid 58 residue protein aprotinin, which had been shown to be processed by DPIV, indicate that the Arg1-Pro2 N terminus can access the DPIV active site only upon widening of its side openings, probably by separation of the first and the last propeller blades, and/or of the catalytic and the propeller domain.

2-[3-[2-[(2S)-2-Cyano-1-pyrrolidinyl]-2-oxoethylamino]-3-methyl-1-oxobutyl]- 1,2,3,4-tetrahydroisoquinoline: A Potent, Selective, and Orally Bioavailable Dipeptide-Derived Inhibitor of Dipeptidyl Peptidase IV

Dipeptidyl peptidase IV (DPP-IV) inhibitors are expected to become a new type of antidiabetic drugs. Most known DPP-IV inhibitors often resemble the dipeptide cleavage products, with a proline mimic at the P1 site. As off-target inhibitions of DPP8 and/or DPP9 have shown profound toxicities in the in vivo studies, it is important to develop selective DPP-IV inhibitors for clinical usage. To achieve this, a new class of 2-[3-[[2-[(2S)-2-cyano-1-pyrrolidinyl]-2-oxoethyl]amino]-1-oxopropyl]-based DPP-IV inhibitors was synthesized. SAR studies resulted in a number of DPP-IV inhibitors, having IC(50) values of <50 nM with excellent selectivity over both DPP8 (IC(50) > 100 microM) and DPP-II (IC(50) > 30 microM). Compound 21a suppressed the blood glucose elevation after an oral glucose challenge in Wistar rats and also inhibited plasma DPP-IV activity for up to 4 h in BALB/c mice. The results show that compound 21a possesses in vitro and in vivo activities comparable to those of NVP-LAF237 (4), which is in clinical development.

Enzymatic ability of Bifidobacterium animalis subsp. lactis to hydrolyze milk proteins: identification and characterization of endopeptidase O

The proteolytic system of Bifidobacterium animalis subsp. lactis was analyzed, and an intracellular endopeptidase (PepO) was identified and characterized. This work reports the first complete cloning, purification, and characterization of a proteolytic enzyme in Bifidobacterium spp. Aminopeptidase activities (general aminopeptidases, proline iminopeptidase, X-prolyl dipeptidylaminopeptidase) found in cell extracts of B. animalis subsp. lactis were higher for cells that had been grown in a milk-based medium than for those grown in MRS. A high specific proline iminopeptidase activity was observed in B. animalis subsp. lactis. Whole cells and cell wall-bound protein fractions showed no caseinolytic activity; however, the combined action of intracellular proteolytic enzymes could hydrolyze casein fractions rapidly. The endopeptidase activity of B. animalis subsp. lactis was examined in more detail, and the gene encoding an endopeptidase O in B. animalis subsp. lactis was cloned and overexpressed in Escherichia coli. The deduced amino acid sequence for B. animalis subsp. lactis PepO indicated that it is a member of the M13 peptidase family of zinc metallopeptidases and displays 67.4% sequence homology with the predicted PepO protein from Bifidobacterium longum. The recombinant enzyme was shown to be a 74-kDa monomer. Activity of B. animalis subsp. lactis PepO was found with oligopeptide substrates of at least 5 amino acid residues, such as met-enkephalin, and with larger substrates, such as the 23-amino-acid peptide alpha s1-casein(f1-23). The predominant peptide bond cleaved by B. animalis subsp. lactis PepO was on the N-terminal side of phenylalanine residues. The enzyme also showed a post-proline secondary cleavage site.

Isoforms of dipeptidyl aminopeptidase IV from Pseudomonas sp. WO24: role of the signal sequence and overexpression in Escherichia coli

The complete nucleotide sequence of dipeptidyl aminopeptidase IV (DAP IV) from Pseudomonas sp. WO24 was determined. Nucleotide sequence analysis revealed an open reading frame of 2238bp, which was assigned to dap4 by N-terminal and internal amino acid sequences previously reported. The predicted amino acid sequence of DAP IV contains a serine protease Gly-X-Ser-X-Gly-Gly consensus motif and displays extensive homology to DAP IVs and the homologous proteins from eukaryotes and bacteria, belonging to the prolyl oligopeptidase family S9. In Pseudomonas sp. WO24, DAP IV is expressed as 82 and 84-kDa isoforms, having two Met, Met-1 and Met-12, in its N-terminal sequence. Met-1 of DAP IV was mutated to Gly and Met-12 was mutated to Ile, and we overexpressed the two mutated genes in Escherichia coli and obtained the recombinant 82 and 84-kDa proteins from the periplasm and the cytoplasm, respectively, suggesting that the 82 and 84-kDa isoforms are derived from the same gene and localize to different compartments in the cell. We developed purification steps for activting a large amount of 84-kDa isoform protein that will be useful for producing protein for crystallographic studies.

VSL#3 probiotic preparation has the capacity to hydrolyze gliadin polypeptides responsible for Celiac Sprue

The native structure and distribution of gliadin epitopes responsible for Celiac Sprue (CS) may be influenced by cereal food processing. This work was aimed at showing the capacity of probiotic VSL#3 to decrease the toxicity of wheat flour during long-time fermentation. VSL#3 (10(9) cfu/ml) hydrolyzed completely the alpha2-gliadin-derived epitopes 62-75 and 33-mer (750 ppm). Two-dimensional electrophoresis, immunological (R5 antibody) and mass spectrometry analyses showed an almost complete degradation of gliadins during long-time fermentation of wheat flour by VSL#3. Gliadins non-hydrolyzed during fermentation by VSL#3 were subjected to peptic-tryptic (PT) digestion and analyzed by CapLC-ESI-Q-ToF-MS (Capillary Liquid Chromatography-Electrospray Ionization-Quadrupole-Time of Flight-Mass Spectrometry). Search for several epitopes showed the only presence of alpha2-gliadin-fragment 62-75 at a very low concentration (sub-ppm range). Compared to IEC-6 cells exposed to intact gliadins extracted from the chemically acidified dough (control), VSL#3 pre-digested gliadins caused a less pronounced reorganization of the intracellular F-actin which was mirrored by an attenuated effect on intestinal mucosa permeability. The release of zonulin from intestinal epithelial cells treated with gliadins was considerably lower when digested with VSL#3. Agglutination test on K 562 (S) cells showed that the PT-digest of wheat flour treated with VSL#3 increased the Minimal Agglutinating Activity of ca. 100 times. Wheat proteins were extracted from doughs and subjected to PT digestion. Compared to PT-digest from chemically acidified dough, celiac jejunal biopsies exposed to the PT-digest from the dough fermented by VSL#3 did not show an increase of the infiltration of CD3(+) intraepithelial lymphocytes. Proteolytic activity by probiotic VSL#3 may have an importance during food processing to produce pre-digested and tolerated gliadins for increasing the palatability of gluten-free products.

Synthesis and Characterization of the Novel Fluorescent Prolyl Oligopeptidase Inhibitor 4-Fluoresceinthiocarbamoyl- 6-aminocaproyl-l-prolyl-2(S)-(Hydroxy- acetyl)pyrrolidine

The synthesis and characterization of the first fluorescent prolyl oligopeptidase inhibitor 4-fluoresceinthiocarbamoyl-6-aminocaproyl-L-prolyl-2(S)-(hydroxyacetyl)pyrrolidine is described. This compound has an IC50 value of 0.83 nM and a dissociation half-life of 160 min, and its fluorescence signal is detectable using standard filters for fluorescein. These properties make this compound a suitable probe for visualizing prolyl oligopeptidase in various applications.

Characterization of the dinuclear metal center ofPyrococcus furiosusprolidase by analysis of targeted mutants

Prolidases are dipeptidases specific for cleavage of Xaa-Pro dipeptides. Pyrococcus furiosus prolidase is a homodimer having one Co-bound dinuclear metal cluster per monomer with one tightly bound Co(II) site and the other loosely bound (Kd 0.24 mM). To identify which Co site is tight-binding and which is loose-binding, site-directed mutagenesis was used to modify amino acid residues that participate in binding the Co1 (E-313 and H-284), the Co2 site (D-209) or the bidentate ligand (E-327). Metal-content, enzyme activity and CD-spectra analyses of D209A-, H284L-, and E327L-prolidase mutants show that Co1 is the tight-binding and Co2 the loose-binding metal center.