Prolyl endopeptidase from Flavobacterium meningosepticum: cloning and sequencing of the enzyme gene

High-level production of Aspergillus niger prolyl endopeptidase from agricultural residue and its application in beer brewing

BACKGROUND

Prolyl endopeptidase from Aspergillus niger (AN-PEP) is a prominent serine proteinase with various potential applications in the food and pharmaceutical industries. However, the availability of efficient and low-cost AN-PEP remains a challenge owing to its low yield and high fermentation cost.

RESULTS

Here, AN-PEP was recombinantly expressed in Trichoderma reesei (rAN-PEP) under the control of the cbh1 promoter and its secretion signal. After 4 days of shaking flask cultivation with the model cellulose Avicel PH101 as the sole carbon source, the extracellular prolyl endopeptidase activity reached up to 16.148 U/mL, which is the highest titer reported to date and the secretion of the enzyme is faster in T. reesei than in other eukaryotic expression systems including A. niger and Komagataella phaffii. Most importantly, when cultivated on the low-cost agricultural residue corn cob, the recombinant strain was found to secret a remarkable amount of rAN-PEP (37.125 U/mL) that is twice the activity under the pure cellulose condition. Furthermore, treatment with rAN-PEP during beer brewing lowered the content of gluten below the ELISA kit detection limit (< 10 mg/kg) and thereby, reduced turbidity, which would be beneficial for improving the non-biological stability of beer.

CONCLUSION

Our research provides a promising approach for industrial production of AN-PEP and other enzymes (proteins) from renewable lignocellulosic biomass, which provides a new idea with relevant researchers for the utilization of agricultural residues.

Efficient Hydrolysis of Gluten-Derived Celiac Disease-Triggering Immunogenic Peptides by a Bacterial Serine Protease from Burkholderia gladioli

Celiac disease is an autoimmune disorder triggered by toxic peptides derived from incompletely digested glutens in the stomach. Peptidases that can digest the toxic peptides may formulate an oral enzyme therapy to improve the patients’ health condition. Bga1903 is a serine endopeptidase secreted by Burkholderia gladioli. The preproprotein of Bga1903 consists of an N-terminal signal peptide, a propeptide region, and an enzymatic domain that belongs to the S8 subfamily. Bga1903 could be secreted into the culture medium when it was expressed in E. coli. The purified Bga1903 is capable of hydrolyzing the gluten-derived toxic peptides, such as the 33- and 26-mer peptides, with the preference for the peptide bonds at the carbonyl site of glutamine (P1 position). The kinetic assay of Bga1903 toward the chromogenic substrate Z-HPQ-pNA at 37 °C, pH 7.0, suggests that the values of Km and k_cat are 0.44 ± 0.1 mM and 17.8 ± 0.4 s⁻¹, respectively. The addition of Bga1903 in the wort during the fermentation step of beer could help in making gluten-free beer. In summary, Bga1903 is usable to reduce the gluten content in processed foods and represents a good candidate for protein engineering/modification aimed to efficiently digest the gluten at the gastric condition.

Mycobacterium tuberculosis Prolyl Oligopeptidase Induces In vitro Secretion of Proinflammatory Cytokines by Peritoneal Macrophages

Tuberculosis (TB) is a disease that leads to death over 1 million people per year worldwide and the biological mediators of this pathology are poorly established, preventing the implementation of effective therapies to improve outcomes in TB. Host-bacterium interaction is a key step to TB establishment and the proteases produced by these microorganisms seem to facilitate bacteria invasion, migration and host immune response evasion. We presented, for the first time, the identification, biochemical characterization, molecular dynamics (MDs) and immunomodulatory properties of a prolyl oligopeptidase (POP) from Mycobacterium tuberculosis (POPMt). POP is a serine protease that hydrolyzes substrates with high specificity for proline residues and has already been characterized as virulence factor in infectious diseases. POPMt reveals catalytic activity upon N-Suc-Gly-Pro-Leu-Gly-Pro-AMC, a recognized POP substrate, with optimal activity at pH 7.5 and 37°C. The enzyme presents K_M and K_cat/K_M values of 108 μM and 21.838 mM^-1 s^-1, respectively. MDs showed that POPMt structure is similar to that of others POPs, which consists of a cylindrical architecture divided into an α/β hydrolase catalytic domain and a β-propeller domain. Finally, POPMt was capable of triggering in vitro secretion of proinflammatory cytokines by peritoneal macrophages, an event dependent on POPMt intact structure. Our data suggests that POPMt may contribute to an inflammatory response during M. tuberculosis infection.

Cloning and expression of a novel prolyl endopeptidase from Aspergillus oryzae and its application in beer stabilization

A novel prolyl endopeptidase gene from Aspergillus oryzae was cloned and expressed in Pichia pastoris. Amino acid sequence analysis of the prolyl endopeptidase from Aspergillus oryzae (AO-PEP) showed that this enzyme belongs to a class serine peptide S28 family. Expression, purification and characterization of AO-PEP were analyzed. The optimum pH and temperature were pH 5.0 and 40 °C, respectively. The enzyme was activated and stabilized by metal ion Ca2+ and inhibited by Zn2+, Mn2+, Al3+, and Cu2+. The K  m and k  cat values of the purified enzyme for different substrates were evaluated. The results implied that the recombinant AO-PEP possessed higher affinity for the larger substrate. A fed-batch strategy was developed for the high-cell-density fermentation and the enzyme activity reached 1,130 U/l after cultivation in 7 l fermentor. After addition of AO-PEP during the fermentation phase of beer brewing, demonstrated the potential application of AO-PEP in the non-biological stability of beer, which favor further industrial development of this new enzyme in beer stabilization, due to its reducing operational costs, as well as no beer losses unlike regeneration process and beer lost with regenerated polyvinylpolypyrrolidone system.

Generation of food-grade recombinant Lactobacillus casei delivering Myxococcus xanthus prolyl endopeptidase

Prolyl endopeptidases (PEP) (EC 3.4.21.26), a family of serine proteases with the ability to hydrolyze the peptide bond on the carboxyl side of an internal proline residue, are able to degrade immunotoxic peptides responsible for celiac disease (CD), such as a 33-residue gluten peptide (33-mer). Oral administration of PEP has been suggested as a potential therapeutic approach for CD, although delivery of the enzyme to the small intestine requires intrinsic gastric stability or advanced formulation technologies. We have engineered two food-grade Lactobacillus casei strains to deliver PEP in an in vitro model of small intestine environment. One strain secretes PEP into the extracellular medium, whereas the other retains PEP in the intracellular environment. The strain that secretes PEP into the extracellular medium is the most effective to degrade the 33-mer and is resistant to simulated gastrointestinal stress. Our results suggest that in the future, after more studies and clinical trials, an engineered food-grade Lactobacillus strain may be useful as a vector for in situ production of PEP in the upper small intestine of CD patients.

Low molecular weight inhibitors of Prolyl Oligopeptidase: a review of compounds patented from 2003 to 2010

INTRODUCTION

Prolyl Oligopeptidase (POP) is a serine peptidase that cleaves post-proline bonds in short peptides. Besides the direct hydrolytic regulation function over peptides, neuropeptides and peptide hormones, POP is probably involved in the regulation of the inositol pathway and participates in protein-protein interactions. Experimental data show that POP inhibitors have neuroprotective, anti-amnesic and cognition-enhancing properties. These compounds are considered therapeutic agents of interest for the treatment of cognitive deficits related to neuropsychiatric and neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Recent findings pointed to the involvement of POP in angiogenesis, although the exact mechanism is still under study.

AREAS COVERED

This review comprises patents and patent applications involving POP inhibitors patented between 2003 and 2010, classified as peptidomimetics, heteroaryl ketones and alkaloids. The binding processes and the mechanisms of inhibition of these inhibitors are also discussed, together with their in vivo effects.

EXPERT OPINION

The major part of the repertory of POP inhibitors derived from systematical modification of the canonical compound benzyloxycarbonyl-prolyl-prolinal (ZPP). Nevertheless, only two of them have progressed into the clinical trials. One possible reason for this failure is the lack of studies concerning pharmacodynamics, pharmacokinetics and toxicity, together with the absence of suitable animal models. Moreover, POP is still not a well-defined therapeutic target. Further studies are required for the elucidation of the biological role of POP and to validate the therapeutic action of inhibitors in cognitive processes. In contrast, the involvement of POP in protein-protein interactions together with the recent evidences in angiogenesis opens alternative approaches to the traditional active site-directed inhibitors, as well as new therapeutic applications.

Prolyl endopeptidase mRNA expression in the central nervous system during rat development

Prolyl endopeptidase (PEP) is a serine protease that cleaves small peptides at the carboxyl side of L-proline. PEP has been reported to have important functions in the brain being implicated in learning and memory processes, psychological disorders and neurodegenerative diseases. Several PEP substrates have been shown to play a role during brain development and this observation led us to investigate the expression of PEP mRNA in the rat brain and spinal cord, from embryo to adult stages. In situ hybridization revealed that PEP mRNA is expressed early, from embryonic day 15, notably in germinative areas including the neocortical, hippocampal, pallidal, thalamic, anterior hypothalamic, tectal, cerebellar, pontine and medullary neuroepithelia. PEP mRNA was also found in the differentiating fields of the olfactory bulb, the orbital and cingulate cortex, the hippocampal formation, the cortical plate and the subventricular zone of the cortex. Quantitative RT-PCR analysis in various brain areas and the spinal cord showed that PEP mRNA levels are more abundant during the perinatal stages, coinciding with a period of neuronal migration and differentiation. From then on, PEP mRNA expression decreased, reaching its lowest levels at adulthood. Overall, the present data support the possibility that PEP exerts specific functions related to neurodevelopment besides those proposed to date.

Fluorescence resonance energy transfer (FRET) peptides and cycloretro-inverso peptides derived from bradykinin as substrates and inhibitors of prolyl oligopeptidase

Prolyl oligopeptidase (POP, EC 3.4.21.26) is a member of a family of serine peptidases with post-proline cleaving activity towards peptides. It is located in the cytosol in active form but without hydrolytic activity on proteins or peptides higher than 30 amino acids. Its function is not well defined, but it is involved in central nervous system disorders. Here, we studied the substrate specificity of wild type POP (POPwt) and its C255T variant lacking the non-catalytic Cys(255). This residue is located in the seven-bladed beta-propeller domain that regulates the activity of POP. Fluorescence resonance energy transfer (FRET) peptides were used with sequences derived from bradykinin-containing region of human kininogen and flanked by Abz (ortho-aminobenzoic acid) and EDDnp [N-ethylenediamine-(2,4-dinitrophenyl)]. The peptide Abz-GFSPFRQ-EDDnp was taken as leader substrate for the synthesis of five series of peptides modified at the P(3), P(2), P'(1), P'(2) and P'(3) residues. The optimal amino acids in each position for POPwt resulted in the sequence RRPYIR that is very similar to the C-terminal sequence of neurotensin. The cyclic peptides c(G((n))FSPFR) (n=1-4) were hydrolyzed by POP; their cycloretro and cycloretro-inverso analogues were inhibitors in the micromolar range. The differences between POPwt and its C255T mutant in the hydrolysis of the series derived from Abz-GFSPFRQ-EDDnp were restricted to the non-prime site of the substrates. The kinetic data of hydrolysis and inhibition by the cyclic peptides are consistent with the structures of POP-substrate/inhibitor complexes and with the substrate specificity data obtained with linear FRET peptides. All together, these results give information about the POP-substrate/inhibitor interactions that further complete knowledge of this important oligopeptidase.

[Biochemistry and structural biology of microbial enzymes and their medical applications]

Microbial enzymes were studied from two medicinal viewpoints. First, we examined proline-specific peptidases from pathogenic microorganisms. We found several proline-specific peptidases in pathogenic bacteria. Among them, prolyl tripeptidyl aminopeptidase from Porphylomonas gingivals and prolyl aminopeptidase from Serratia marcescens were crystallized. The complex structures of those enzymes and inhibitors were clarified in X-ray crystallography. Aminopeptidase N, which has wide specificity for amino acids, was distributed in the pathogens. The crystal structure of the aminopeptidase N elucidated the reasons for its wide substrate specificity but inertness to the X-Pro bond. It was also revealed that proline-specific peptidases and aminopeptidase N cooperatively degrade collagen for the uptake of amino acids as nutrition when these bacteria infect cells. Second, we applied enzymes from microorganisms to diagnostic analyses. We found a series of creatinine-metabolizing enzymes in Pseudomonas putida. Creatininase, creatinase, and sarcosine oxidase were coupled and have been developed for a diagnostic analysis kit that examines renal function. The structures of the native and the Mn2+-activated creatininases were determined in X-ray crystallography. Based on the structure, the activated enzyme was used for an improved assay kit. The structure of D-3-hydroxybutyrate dehydrogenase from Pseudomonas fragi was also clarified in crystallography. The enzyme is useful for diagnostic analysis of diabetes mellitus while monitoring ketone bodies.

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.

Crystal structure and mechanism of tripeptidyl activity of prolyl tripeptidyl aminopeptidase from Porphyromonas gingivalis

The crystal structure of prolyl tripeptidyl aminopeptidase from Porphyromonas gingivalis was determined. Prolyl tripeptidyl aminopeptidase consists of beta-propeller and catalytic domains, and a large cavity between the domains; this structure is similar to dipeptidyl aminopeptidase IV. A catalytic triad (Ser603, His710, and Asp678) was located in the catalytic domain; this triad was virtually identical to that of the enzymes belonging to the prolyl oligopeptidase family. The structure of an inactive S603A mutant enzyme complexed with a substrate was also determined. The pyrrolidine ring of the proline residue appeared to fit into a hydrophobic pocket composed of Tyr604, Val629, Trp632, Tyr635, Tyr639, Val680, and Val681. There were characteristic differences in the residues of the beta-propeller domain, and these differences were related to the substrate specificity of tripeptidyl activity. The N-terminal amino group was recognized by salt bridges, with two carboxyl groups of Glu205 and Glu206 from a helix in dipeptidyl aminopeptidase IV. In prolyl tripeptidyl aminopeptidase, however, the Glu205 (located in the loop) and Glu636 were found to carry out this function. The loop structure provides sufficient space to accommodate three N-terminal residues (Xaa-Xaa-Pro) of substrates. This is the first report of the structure and substrate recognition mechanism of tripeptidyl peptidase.

Protamine: a unique and potent inhibitor of oligopeptidase B

Oligopeptidase B is a serine endopeptidase found in prokaryotes, unicellular eukaryotes and higher plants. The enzyme has been shown recently to play a central role in the pathogenesis of several parasitic diseases such as African trypanosomiasis, and to be a potential therapeutic target. This study reports that protamine, a basic peptide rich in arginine, is a potent inhibitor at the nanomolar level of oligopeptidase B from E. coli and wheat. Protamines 1B, 2C, 3A and TP17 displayed similar inhibitory activities and were capable of binding strongly to oligopeptidase B without proteolytic cleavage. The concentration of protamine needed for 50% inhibition (IC50) of oligopeptidase B was 10(4)-fold lower than the IC50 of trypsin. Oligopeptidase B was highly sensitive to inhibition by protamines even in the presence of serum (IC50, 1 microM). These data indicate that protamines might provide information useful for the design of more specific synthetic oligopeptidase B inhibitors.

Identification of the reactive cysteine residues in oligopeptidase B from Trypanosoma brucei

Oligopeptidase B (OpdB) from Trypanosoma brucei is a candidate therapeutic target in African trypanosomiasis. OpdB is an atypical serine peptidase, since activity is inhibited by thiol-blocking reagents and enhanced by reducing agents. We have identified C256 as the reactive cysteine residue that mediates OpdB inhibition by N-ethylmaleimide and iodoacetic acid. Modeling studies suggest that C256 adducts occlude the P(1) substrate-binding site, preventing substrate binding. We further demonstrate that C559 and C597 are responsible for the thiol-enhancement of OpdB activity. These studies may facilitate the development of specific OpdB inhibitors with therapeutic potential, by exploiting these unique properties of this enzyme.

Comparative biochemical analysis of three bacterial prolyl endopeptidases: implications for coeliac sprue

Prolyl endopeptidases have potential for treating coeliac sprue, a disease of the intestine caused by proteolytically resistant peptides from proline-rich prolamins of wheat, barley and rye. We compared the properties of three similar bacterial prolyl endopeptidases, including the known enzymes from Flavobacterium meningosepticum (FM) and Sphingomonas capsulate (SC) and a novel enzyme from Myxococcus xanthus (MX). These enzymes were interrogated with reference chromogenic substrates, as well as two related gluten peptides (PQPQLPYPQPQLP and LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF), believed to play a key role in coeliac sprue pathogenesis. In vitro and in vivo studies were conducted to evaluate the activity, specificity and acid/protease stability of the enzymes. All peptidases were relatively resistant to acid, pancreatic proteases and membrane peptidases of the small intestinal mucosa. Although their activities against reference substrates were similar, the enzymes exhibited substantial differences with respect to chain length and subsite specificity. SC hydrolysed PQPQLPYPQPQLP well, but had negligible activity against LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF. In contrast, the FM and MX peptidases cleaved both substrates, although the FM enzyme acted more rapidly on LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF than MX. Whereas the FM enzyme showed a preference for Pro-Gln bonds, SC cleaved both Pro-Gln and Pro-Tyr bonds with comparable efficiency, and MX had a modest preference for Pro-(Tyr/Phe) sites over Pro-Gln sites. While a more comprehensive understanding of sequence and chain-length specificity may be needed to assess the relative utility of alternative prolyl endopeptidases for treating coeliac sprue, our present work has illustrated the diverse nature of this class of enzymes from the standpoint of proteolysing complex substrates such as gluten.

Structural and mechanistic analysis of two prolyl endopeptidases: role of interdomain dynamics in catalysis and specificity

Prolyl endopeptidases (PEPs) are a unique class of serine proteases with considerable therapeutic potential for the treatment of celiac sprue. The crystal structures of two didomain PEPs have been solved in alternative configurations, thereby providing insights into the mode of action of these enzymes. The structure of the Sphingomonas capsulata PEP, solved and refined to 1.8-A resolution, revealed an open configuration of the active site. In contrast, the inhibitor-bound PEP from Myxococcus xanthus was crystallized (1.5-A resolution) in a closed form. Comparative analysis of the two structures highlights a critical role for the domain interface in regulating interdomain dynamics and substrate specificity. Structure-based mutagenesis of the M. xanthus PEP confirms an important role for several interfacial residues. A salt bridge between Arg-572 and Asp-196/Glu-197 appears to act as a latch for opening or closing the didomain enzyme, and Arg-572 and Ile-575 may also help secure the incoming peptide substrate to the open form of the enzyme. Arg-618 and Asp-145 are responsible for anchoring the invariant proline residue in the active site of this postproline-cleaving enzyme. A model is proposed for the docking of a representative substrate PQPQLPYPQPQLP in the active site, where the N-terminal substrate residues interact extensively with the catalytic domain, and the C-terminal residues stretch into the propeller domain. Given the promise of the M. xanthus PEP as an oral therapeutic enzyme for treating celiac sprue, our results provide a strong foundation for further optimization of the PEP's clinically useful features.

Characterization of two membrane-associated protease genes obtained from screening out-membrane protein genes of Flavobacterium columnare G4

In order to identify genes encoding the outer membrane proteins (OMPs) of the myxobacter Flavobacterium columnare G(4), the expression library of the bacterium was screened by using rabbit antisera developed against its OMPs. Positive colonies of Escherichia coli M15 containing fragments encoding the bacterial OMPs were selected for cloning the relevant genes by genomic walking methods. Two genes encoding a membrane-associated zinc metalloprotease and prolyl oligopeptidase are reported in this paper. The membrane-associated zinc metalloprotease gene (map) is 1800 bp in length, coding for 449 amino acids (aa). Despite the presence of a conserved motif HEXXH for all metalloproteases, the special HEXXH approximately 32 aa approximately E motif of the F. columnare G(4) Map and its low level of identity with other reported zinc-containing metalloproteases may imply that the membrane-associated zinc metalloprotease of F. columnare G(4) represents a new family of zincins. The gene encoding prolyl oligopeptidase (Pop), a serine proteinase, is 2352 bp in length, coding for 649 aa. Sequence homology analysis revealed that the Pop is also novel as it has < 50% identity with other reported prolyl oligopeptidase family proteins. The present study represents the first to employ anti-fish bacterial OMP sera to screen genes of membrane-associated proteases of fish pathogenic bacteria, and to provide necessary information for the examination of the role of the two genes in the infection and pathogenesis of F. columnare.

Intestinal digestive resistance of immunodominant gliadin peptides

Two recently identified immunodominant epitopes from alpha-gliadin account for most of the stimulatory activity of dietary gluten on intestinal and peripheral T lymphocytes in patients with celiac sprue. The proteolytic kinetics of peptides containing these epitopes were analyzed in vitro using soluble proteases from bovine and porcine pancreas and brush-border membrane vesicles from adult rat intestine. We showed that these proline-glutamine-rich epitopes are exceptionally resistant to enzymatic processing. Moreover, as estimated from the residual peptide structure and confirmed by exogenous peptidase supplementation, dipeptidyl peptidase IV and dipeptidyl carboxypeptidase I were identified as the rate-limiting enzymes in the digestive breakdown of these peptides. A similar conclusion also emerged from analogous studies with brush-border membrane from a human intestinal biopsy. Supplementation of rat brush-border membrane with trace quantities of a bacterial prolyl endopeptidase led to the rapid destruction of the immunodominant epitopes in these peptides. These results suggest a possible enzyme therapy strategy for celiac sprue, for which the only current therapeutic option is strict exclusion of gluten-containing food.

Substrate recognition properties of oligopeptidase B from Salmonella enterica serovar Typhimurium

Oligopeptidase B (OpdB) is a serine peptidase broadly distributed among unicellular eukaryotes, gram-negative bacteria, and spirochetes which has emerged as an important virulence factor and potential therapeutic target in infectious diseases. We report here the cloning and expression of the opdB homologue from Salmonella enterica serovar Typhimurium and demonstrate that it exhibits amidolytic activity exclusively against substrates with basic residues in P(1). While similar to its eukaryotic homologues in terms of substrate specificity, Salmonella OpdB differs significantly in catalytic power and inhibition and activation properties. In addition to oligopeptide substrates, restricted proteolysis of histone proteins was observed, although no cleavage was seen at or near residues that had been posttranslationally modified or at defined secondary structures. This supports the idea that the catalytic site of OpdB may be accessible only to unstructured oligopeptides, similar to the closely related prolyl oligopeptidase (POP). Salmonella OpdB was employed as a model enzyme to define determinants of substrate specificity that distinguish OpdB from POP, which hydrolyzes substrates exclusively at proline residues. Using site-directed mutagenesis, nine acidic residues that are conserved in OpdBs but absent from POPs were converted to their corresponding residues in POP. In this manner, we identified a pair of glutamic acid residues, Glu(576) and Glu(578), that define P(1) specificity and direct OpdB cleavage C terminal to basic residues. We have also identified a second pair of residues, Asp(460) and Asp(462), that may be involved in defining P(2) specificity and thus direct preferential cleavage by OpdB after pairs of basic residues.

Expression and localization of prolyl oligopeptidase in mouse testis and its possible involvement in sperm motility

Prolyl oligopeptidase (POP) expression in mouse testis during sexual maturation was examined. Northern blot analysis showed that POP mRNA expression was highest at 2 weeks of age, and gradually reduced thereafter. However, enzyme activity was almost constant during the examined period. In situ hybridization study revealed a change in the expression site of POP mRNA in testis during sexual maturation. Positive signals were detected in all types of cells in the seminiferous tubules before maturation, and were restricted to spermatids at the spermatogenesis cycle stages I-VIII in adult mice. POP was detected in the insoluble fraction of sperm by Western blot analysis. Immunohistochemical analyses showed that POP is localized in the spermatids at steps 12-16 of spermiogenesis and in the midpiece of the sperm fragellum. It was also found that specific POP inhibitors, poststatin and benzyloxycarbonyl-proline-prolinal, suppressed sperm motility. These results suggest that POP may be involved in meiosis of spermatocytes, differentiation of spermatids, and sperm motility in the mouse.

Purification and characterization of a Z-pro-prolinal-insensitive Z-Gly-Pro-7-amino-4-methyl coumarin-hydrolyzing peptidase from bovine serum--a new proline-specific peptidase

The study of a new proline-specific peptidase from bovine serum is presented. The enzyme readily cleaves the prolyl oligopeptidase (PO) substrate Z-Gly-Pro-MCA, liberating the fluorophore MCA, thus allowing quantification of enzyme activity. Unlike PO, however, this peptidase is completely insensitive to the PO-specific inhibitor Z-Pro-prolinal and has been designated Z-Pro-prolinal-insensitive Z-Gly-Pro-MCA-hydrolyzing peptidase (ZIP). The two peptidases were successfully separated from each other by phenyl Sepharose hydrophobic interaction chromatography and the subsequent purification focused on the isolation of ZIP from bovine serum. In addition to phenyl Sepharose, calcium phosphate cellulose and DEAE anion-exchange chromatography were employed in the purification, with an overall enzyme yield of 33% and a purification factor of 4023. SDS-PAGE and size-exclusion chromatography indicated a dimeric structure with a relative molecular mass of 174 kDa. The enzyme was stable over the pH range 2.5-10.0. Optimal activity was detected in the pH range 7.4-8.0. Isoelectric focusing revealed a pI of 5.68. Inhibition by AEBSF suggests the peptidase may be a serine protease and ZIP possibly contains a cysteine residue near the active site. alpha(2)M failed to inhibit activity, suggesting oligopeptidase specificity. HPLC analysis revealed a broad substrate specificity for proline-containing peptides. Kinetic analysis indicated that ZIP had a high affinity for Z-Gly-Pro-MCA with a K(m) of 54 microM deduced. Bovine serum ZIP exhibits biophysical characteristics both similar to and different from those of PO isolated from a number of sources and may serve an important physiological function in the degradation of bioactive oligopeptides.

Catalysis of serine oligopeptidases is controlled by a gating filter mechanism

Proteases have a variety of strategies for selecting substrates in order to prevent uncontrolled protein degradation. A recent crystal structure determination of prolyl oligopeptidase has suggested a way for substrate selection involving an unclosed seven-bladed beta-propeller domain. We have engineered a disulfide bond between the first and seventh blades of the propeller, which resulted in the loss of enzymatic activity. These results provided direct evidence for a novel strategy of regulation in which oscillating propeller blades act as a gating filter during catalysis, letting small peptide substrates into the active site while excluding large proteins to prevent accidental proteolysis.

Analysis of a local fitness landscape with a model of the rough Mt. Fuji-type landscape: application to prolyl endopeptidase and thermolysin

A method of analysis of a local fitness landscape for a current biopolymer is presented. Based on the assumption of additivity of mutational effects in the biopolymer, we assigned a site-fitness to each residue at each site. The assigned values of site-fitnesses were obtained by the least-squares method to minimize discrepancies between experimental fitnesses and theoretical ones. As test cases, we analyzed a section of a local landscape for the thermostability of prolyl endopeptidase and that for the enzymatic activity of thermolysin. These sections were proved to be of the rough Mt. Fuji-type with straight theta values of larger than 1.0, where straight theta is defined as the ratio of the "mean slope" to the "degree of roughness" on the fitness surface. Furthermore, we theoretically explained discrepancies between the fitnesses of multiple mutants and those predicted based on strict additivity of the component mutations by using a model of the rough Mt. Fuji-type landscape. According to this model, the discrepancies depend on the local landscape property (such as the straight theta value) and the location of the wild type on the landscape and the mean change in fitness by the component mutations. Our results suggest that this model may provide a good approximation of real sections of local landscapes for current biopolymers phenomenologically.

The noncatalytic beta-propeller domain of prolyl oligopeptidase enhances the catalytic capability of the peptidase domain

Prolyl oligopeptidase, which is involved in memory disorders, is a member of a new family of serine peptidases. In addition to the peptidase domain, the enzyme contains a beta-propeller, which excludes large peptides from the active site. The enzyme is inhibited with thiol reagents, possibly by reacting with Cys-255 located close to the substrate binding site. This assumption was tested with the Cys-255 --> Thr, Cys-255 --> Ala, and Cys-255 --> Ser variants of prolyl oligopeptidase. In contrast to the wild type enzyme, the Cys-255 --> Thr variant was not inhibited with N-ethylmaleimide, indicating that Cys-255, of the 16 free cysteine residues, exclusively accounts for the enzyme inhibition. Unlike the wild type enzyme that showed a doubly bell-shaped pH rate profile, the modified enzyme displayed a single bell-shaped pH dependence with benzyloxycarbonyl-Gly-Pro-naphthylamide. It was the high pH form of the enzyme that virtually disappeared with all three enzyme variants. A substantial reduction was also observed in k(cat)/K(m) for the aminobenzoyl-Ser-Pro-Phe(NO(2))-Ala-OH substrate. The high pK(a) (9.77) of Cys-255 determined by titration with N-ethylmaleimide excluded the possibility that ionization of the thiol group was responsible for generation of the two active enzyme forms. The impaired activity of the enzyme variants could be rationalized in terms of weaker binding, which manifests itself in high K(m) for substrates and high K(i) for inhibitors, like benzyloxycarbonyl-Gly-Pro-OH and aminobenzoyl-Ser-d-Pro-Phe(NO(2))-Ala-OH. It was concluded that, besides selecting substrates by size, the beta-propeller domain containing Cys-255 remarkably contributed to catalysis of the peptidase domain.

Oligopeptidase B from Trypanosoma brucei, a new member of an emerging subgroup of serine oligopeptidases

Trypanosoma brucei contains a soluble serine oligopeptidase (OP-Tb) that is released into the host bloodstream during infection, where it has been postulated to participate in the pathogenesis of African trypanosomiasis. Here, we report the identification of a single copy gene encoding the T. brucei oligopeptidase and a homologue from the related trypanosomatid pathogen Leishmania major. The enzymes encoded by these genes belong to an emerging subgroup of the prolyl oligopeptidase family of serine hydrolases, referred to as oligopeptidase B. The trypanosomatid oligopeptidases share 70% amino acid sequence identity with oligopeptidase B from the intracellular pathogen Trypanosoma cruzi, which has a demonstrated role in mammalian host cell signaling and invasion. OP-Tb exhibited no activity toward the prolyl oligopeptidase substrate H-Gly-Pro-7-amido-4-methylcoumarin. Instead, it had activity toward substrates of trypsin-like enzymes, particularly those that have basic amino acids in both P(1) and P(2) (e.g. benzyloxycarbonyl-Arg-Arg-7-amido-4-methylcoumarin k(cat)/K(m) = 529 s(-1) microM(-1)). The activity of OP-Tb was enhanced by reducing agents and by polyamines, suggesting that these agents may act as in vivo regulators of OP-Tb activity. This study provides the basis of the characterization of a novel subgroup of serine oligopeptidases from kinetoplastid protozoa with potential roles in pathogenesis.

Structure and localization of the mouse prolyl oligopeptidase gene

We have cloned and characterized the genomic structure of the mouse gene for prolyl oligopeptidase that is mapped to chromosome 10B2-B3. The gene is about 92 kilobases in size and contains 15 exons. All exon-intron junction sequences conform to the GT/AG rule. Comparison with the presumed domain structures of the mouse prolyl oligopeptidase indicates that the propeller domain of the enzyme is encoded by exons 3-10, whereas the catalytic domain is encoded by exons 1-3 and 10-15. The catalytic triad residues are encoded by two exons (Ser(554) on exon 13 and His(680) and Asp(642) on exon 15). The 5'-flanking region of the mouse prolyl oligopeptidase gene has structural features found in housekeeping gene promoters, including a GC-rich segment and an absence of TATA and CAAT boxes. A primer extension assay showed the presence of multiple sites for the initiation of transcription. Transient transfection analysis demonstrated that the 5'-flanking region of the gene can direct efficient expression in COS1 cells. Deletion studies revealed that the downstream 125-base pair sequence of the region is required for promoter activity in the cells.

Identification of a Drosophila prolyl endopeptidase and analysis of its expression

Prolyl endopeptidases (PEPs) are believed to be involved in the metabolism of neuropeptide hormones (reviewed in Mentlein [1988]). Genes encoding PEPs have been isolated from various species, but their expression patterns during development have not been determined. In this study, we isolated a gene encoding a predicted PEP from the fruitfly Drosophila melanogaster. The gene encodes a predicted 756-amino acid protein having extensive sequence similarity to human PEP. We demonstrated that the Drosophila gene (DPEP) is expressed in a spatially restricted pattern in imaginal discs and the larval brain. Our results suggest a role for DPEP in the regional specification of larval tissues. They also provide a starting point for a genetic analysis of the function of this enzyme during development.

Purification and characterization of prolyl endopeptidase from the Pacific herring, Clupea pallasi, and its role in the activation of sperm motility

Protease activities with specificity toward synthetic substrates, Suc-Gly-Pro-Leu-Gly-Pro-MCA for prolyl endopeptidase or collagenase-like peptidase, and Suc-Ala-Ala-Pro-Phe-MCA for chymotrypsin were identified in the detergent-soluble fraction of herring spermatozoa. The enzyme activities increased in the presence of herring sperm-activating protein (HSAP). Among them a prolyl endopeptidase [EC. 3. 4. 21. 26] was purified to near homogeneity from herring testis. The molecular mass of the enzyme was 79 kDa and the properties of the enzyme were quite similar to prolyl endopeptidase from other tissues or cells. Both the enzyme activation and the sperm motility activation by HSAP were inhibited by benzyloxycarbonyl-L-thioproline-thioprolinal, a specific inhibitor for prolyl endopeptidase. Furthermore, the motility activation by HSAP was inhibited by substrates of the prolyl endopeptidase. Western blotting with mouse anti-prolyl endopeptidase serum revealed the presence of 79 kDa prolyl endopeptidase in the tail fraction of herring sperm. These results suggest that prolyl endopeptidase exists on the surface of the sperm tail and interacts with the HSAP.

Cloning of a novel prolidase gene from Aureobacterium esteraromaticum

The prolidase gene from Aureobacterium esteraromaticum was cloned and expressed in Escherichia coli. The cloned enzyme had the same enzymatic properties as the wild-type enzyme. Kinetic analysis of the enzyme indicated that the best substrate was Pro-Hyp, which was not hydrolyzed by other prolidases. Interestingly, there was no homology between the deduced amino acid sequence of A. esteraromaticum prolidase and those of the other sources such as human E. coli and Lactobacillus. However, homology was seen with the yeast hypothetical protein YJL213w, the function of which is unknown. These findings indicate that the A. esteraromaticum prolidase is a novel enzyme different from other prolidases reported to date.

Prolyl endopeptidase from Sphingomonas capsulata: isolation and characterization of the enzyme and nucleotide sequence of the gene

Prolyl endopeptidase (prolyl oligopeptidase, EC 3.4.21.26) was purified from Sphingomonas capsulata IFO 12533, and its gene was cloned and expressed in Escherichia coli. The recombinant enzyme was markedly inhibited by diisopropyl phosphofluoridate and hardly affected by SH reagents or metal chelators, similar to the native enzyme purified from S. capsulata. Nucleotide sequencing analysis revealed an open reading frame of 2169 bp, coding for a protein of 723 amino acids with a predicted molecular weight of 78,433. The amino acid sequence was 39.6, 45.3, 38.9, and 38.3% homologous to Flavobacterium meningosepticum, Aeromonas hydrophila, porcine brain, and human T cell prolyl endopeptidase, respectively. A region near the C-terminus and the region containing the putative catalytic triad residues were highly conserved. The enzyme was crystallized by the hanging drop vapor diffusion method, using ammonium sulfate as a precipitant.

A novel prolyl endopeptidase inhibitor, JTP-4819--its behavioral and neurochemical properties for the treatment of Alzheimer's disease

Formation of beta-amyloid and neurofibrillary tangles in the brain due to genetic or other factors is the most frequent cause of Alzheimer's disease. In addition, marked reduction of certain brain neuropeptide levels is a consistent finding in patients with Alzheimer's disease, together with the deterioration of cholinergic neurons. Currently, there is great demand for the development of new drugs to improve memory deficits or to delay the neurodegenerative process in conditions such as Alzheimer's disease. In this report, the pharmacological actions of JTP-4819, a novel specific prolyl endopeptidase (PEP) inhibitor devised for the treatment of Alzheimer's disease, are reviewed with respect to its effects on PEP activity, neuropeptidergic and cholinergic neurons, and memory-related behavior in rats. We also discuss the possible beneficial effect of JTP-4819 on beta-amyloid metabolism and its potential neuroprotective properties.

Prolyl oligopeptidase: an unusual beta-propeller domain regulates proteolysis

Prolyl oligopeptidase is a large cytosolic enzyme that belongs to a new class of serine peptidases. The enzyme is involved in the maturation and degradation of peptide hormones and neuropeptides, which relate to the induction of amnesia. The 1.4 A resolution crystal structure is presented here. The enzyme contains a peptidase domain with an alpha/beta hydrolase fold, and its catalytic triad (Ser554, His680, Asp641) is covered by the central tunnel of an unusual beta propeller. This domain makes prolyl oligopeptidase an oligopeptidase by excluding large structured peptides from the active site. In this way, the propeller protects larger peptides and proteins from proteolysis in the cytosol. The structure is also obtained with a transition state inhibitor, which may facilitate drug design to treat memory disorders.

The gene encoding dipeptidyl aminopeptidase BI from Pseudomonas sp. WO24: cloning, sequencing and expression in Escherichia coli

We have isolated the dipeptidyl aminopeptidase BI (DAP BI) gene from the plasmid library of Pseudomonas sp. WO24 chromosomal DNA by the enzymatic plate assay using a chromogenic substrate. The DAP BI gene, designated dap b1, was further subcloned and sequenced. Sequence analysis of an approx. 3-kb fragment revealed an open reading frame of 2169 nucleotides, which was assigned to the dap b1 gene by N-terminal and internal amino acid sequences. The predicted amino acid sequence of DAP BI containing a serine protease Gly-X-Ser-X-Gly consensus motif displays extensive homologies to the several proteases belonging to the prolyl oligopeptidase family, a novel serine protease family possessing the catalytic triad with a specific array of Ser, Asp and His in this order, which is the hallmark of the member of this family including DAP IV. The dap b1 gene was expressed in Escherichia coli and the expressed enzyme was purified about 230-fold with 2.6% recovery from the cell-free extracts. The enzymatic properties such as molecular mass, substrate specificity and effect of inhibitor were similar to the native enzyme from Pseudomonas sp. WO24.

Proline specific peptidases

Proline is unique among the 20 amino acids due to its cyclic structure. This specific conformation imposes many restrictions on the structural aspects of peptides and proteins and confers particular biological properties upon a wide range of physiologically important biomolecules. In order to adequately deal with such peptides, nature has developed a group of enzymes that recognise this residue specifically. These peptidases cover practically all situations where a proline residue might occur in a potential substrate. In this paper we endeavour to discuss these enzymes, particularly those responsible for peptide or protein hydrolysis at proline sites. We have detailed their discovery, biochemical attributes and substrate specificities and have provided information as to the methodology used to detect and manipulate their activities. We have also described the roles, or potential roles that these enzymes may play physiologically and the consequences of their dysfunction in varied disease states.

A cytosolic serine endopeptidase from Trypanosoma cruzi is required for the generation of Ca2+ signaling in mammalian cells

An early event in the Trypanosoma cruzi cell invasion process, the recruitment of host lysosomes, led us to investigate the involvement of signal transduction. Infective trypomastigotes were found to contain a soluble Ca2+-signaling activity for mammalian cells that is sensitive to protease inhibitors. Inhibitor and substrate utilization profiles were used to purify a candidate peptidase for involvement in this process, from which we isolated a full-length cDNA clone. The sequence revealed a novel enzyme, denominated T. cruzi oligopeptidase B, which is homologous to members of the prolyl oligopeptidase family of serine hydrolases, known to participate in the maturation of biologically active peptides. The T. cruzi oligopeptidase B was expressed as a fully active product in Escherichia coli, and antibodies to the recombinant enzyme inhibited both peptidase activity and Ca2+ signaling induced in normal rat kidney cells by trypomastigote extracts. Our data suggest that the T. cruzi oligopeptidase B participates in processing events in the cytoplasm of the parasites, generating a factor with Ca2+-signaling activity for mammalian cells.

New fluorogenic substrates for the study of secondary specificity of prolyl oligopeptidase

The secondary specificity of prolyl oligopeptidase (POP) has been studied by using a series of fluorogenic substrates containing the highly fluorescent 7-amino-4-methyl-2-quinolinone (AMeq) marker. The substrates were dipeptides of the general formula Z-X-Pro-NH-Meq, bearing amino acid residues with variable functional groups [Met, Lys(Boc), Lys, His, Ser, Leu, Glu(OMe), Glu, Cys(Bzl)] at the P2 position, and the tripeptide Z-Asn-Cys(Bzl)-Pro-NH-Meq. The kinetic parameters for their hydrolysis by porcine kidney POP were determined at lambda ex = 360 nm and lambda em = 430 nm. All the dipeptide substrates showed a high affinity to the enzyme and could be used for its fluorometric determination. The S2 binding subsite of POP can accommodate amino acid residues with a bulky side group, while it prefers a positively charged group (free Lys) instead of a negatively charged one (free Glu).

Substrates containing phosphorylated residues adjacent to proline decrease the cleavage by proline-specific peptidases

Thirteen dipeptide rho-nitroanilides of the common structure H-Xaa-Pro-4-NA (Xaa = serine, threonine and tyrosine) and seven tripeptide rho-nitroanilides of the common structure H-Gly-Xaa-Pro-4-NA (Xaa = serine or threonine) were prepared and analyzed as substrates of the proline-specific peptidases dipeptidyl peptidase IV and prolyl endopeptidase, respectively. The side chains of the hydroxy amino acids were synthetically modified by various acyl-, benzyl- and phosphate residues. The presence of aliphatic or aromatic residues attached to the side chain of the P2-hydroxy amino acids resulted in no significant change of the specificity constants of the enzyme-catalyzed substrate hydrolysis. In some cases, however, substrate inhibition was observed. In contrast, the reactivity of dipeptidyl peptidase IV and prolyl endopeptidase decreases more than two orders of magnitude towards the phosphorylated di- and tripeptide substrates compared to the hydrolysis of unmodified substrates. The kinetic data obtained with the model compounds suggest that side-chain modification of proline-containing peptide substrates may influence their resistance towards the hydrolytic activity of proline-specific hydrolases. Additionally, the results support that structural changes of the substrate during enzyme-hydrolysis may be involved in the mechanism of action of proline-specific serine peptidases. From this result we speculate that posttranslational phosphorylation of peptide sequences found in protein kinase recognition motifs such as -Xaa-Ser/Thr-Pro-Yaa- and -Xaa-Pro-Ser/Thr-Yaa- may serve as structural determinants that modulate their proteolytic stability.

The purification, characterization and analysis of primary and secondary-structure of prolyl oligopeptidase from human lymphocytes. Evidence that the enzyme belongs to the alpha/beta hydrolase fold family

Prolyl oligopeptidase was isolated and purified to homogeneity from human lymphocytes, yielding a specific activity of 7780 mU/mg. The molecular mass using size-exclusion chromatography matches the 76 kDa obtained by SDS/PAGE. This provides evidence that prolyl oligopeptidase is a monomer. The isoelectric point is 4.8 as judged by isoelectric focusing in free solution. Di-isopropyl fluorophosphate and phenylmethylsulphonyl fluoride completely abolish the activity, classifying the enzyme as a serine proteinase. The inhibition by p-chloromercuribenzoic acid indicates the importance of a free sulfhydryl group near the active-site. alpha 1-Casein and ornithine decarboxylase, two proteins containing a PEST sequence, inhibit prolyl oligopeptidase, but were not hydrolyzed. This demonstrates that prolyl oligopeptidase is not participating in the metabolism of proteins according to a PEST-dependent pathway. alpha 1-Antitrypsin partially inhibits the enzyme but in contrast, aprotinin does not. Its inability to cleave corticotropin-releasing factor, ubiquitin, albumin and aprotinin, together with the hydrolysis of bradykinin between Pro7-Arg8 confirms the affinity of prolyl oligopeptidase for small peptides. Multiple sequence alignment does not reveal any similarity with proteases of known tertiary structure. Secondary-structure prediction displays striking similarity with dipeptidyl peptidase IV and acylaminoacyl peptidase. Two characteristic features of the members of the prolyl oligopeptidase family of serine proteases are high-lighted: the linear arrangement of the catalytic triad is nucleophile-acid-base and the proteolytic cleavage releasing the catalytically active C-terminal region of around 500 amino acids from the N-terminal sequence. Secondary structure prediction and comparison of the active-site of serine proteinases with known three-dimensional coordinates prove that Asp641 is the third member of the catalytic triad. The secondary structural organization of the protease domain of prolyl oligopeptidase is in accordance with the alpha/beta hydrolase fold.

Cloning and sequence analysis of the gene encoding human lymphocyte prolyl endopeptidase

The human cDNA encoding prolyl endopeptidase, a cytoplasmic endoprotease which hydrolyses the peptide bond at the C-terminal side of proline, was sequenced. After the isolation of the 3' terminal fragment of the pep cDNA sequence from a human lymphocyte cDNA library, an approach based on the polymerase chain reaction (PCR) was undertaken to obtain the complete pep cDNA. Overlapping DNA fragments were generated by PCR from cDNA synthesized from human lymphocyte mRNA. The DNA fragments were subcloned and sequenced. The complete cDNA is 2562 nucleotides (nt) in length and contains an open reading frame coding for a protein of 710 amino acids (aa). Comparison of the primary PEP sequences from human lymphocyte and pig brain shows 97% identify. The aa sequence analysis shows homology with bacterial PEPs and with protease II from Escherichia coli. Asp641 probably participates in the active site of PEP.

An endo-acting proline-specific oligopeptidase from Treponema denticola ATCC 35405: evidence of hydrolysis of human bioactive peptides

An endo-acting proline-specific oligopeptidase (prolyl oligopeptidase [POPase], EC 3.4.21.26) was purified to homogeneity from the Triton X-100 extracts of cells of Treponema denticola ATCC 35405 (a human oral spirochete) by a procedure that comprised five successive fast protein liquid chromatography steps. The POPase is a cell-associated 75- to 77-kDa protein with an isoelectric point of ca. 6.5. The enzyme hydrolyzed (optimum pH 6.5) the Pro-pNA bond in carbobenzoxy-Gly-Pro-p-nitroanilide (Z-Gly-Pro-pNA) and bonds at the carboxyl side of proline in several human bioactive peptides, such as bradykinin, substance P, neurotensin, angiotensins, oxytocin, vasopressin, and human endothelin fragment 22-38. The minimum hydrolyzable peptide size was tetrapeptide P3P2P1P'1, while the maximum substrate size was ca. 3 kDa. An imino acid residue in position P1 was absolutely necessary. The hydrolysis of Z-Gly-Pro-pNA was potently inhibited by the following, with the Ki(app) (in micromolar) in parentheses: insulin B-chain (0.7), human endothelin-1 (0.5), neuropeptide Y (1.7), substance P (32.0), T-kinin (4.0), neurotensin (5.0), and bradykinin (16.0). Chemical modification and inhibition studies suggest that the POPase is a serine endopeptidase whose activity depends on the catalytic triad of COOH ... Ser ... His but not on a metal. The amino acid sequence around the putative active-site serine is Gly-Gly-Ser-Asn-Pro-Gly. The enzyme is suggested to contain a reactive cysteinyl residue near the active site. Amino acid residues 4 to 24 of the first 24 N-terminal residues showed a homology of 71% with the POPase precursor from Flavobacterium meningosepticum and considerable homology with the Aeromonas hydrophila POPase. The ready hydrolysis of human bioactive peptides at bonds involving an imino acid residue suggests that enzymes like POPase may contribute to the chronicity of periodontal infections by participating in the peptidolytic processing of those peptides.

Cloning of proline-specific endopeptidase gene from Flavobacterium meningosepticum: expression in Escherichia coli and purification of the heterologous protein

Proline-specific endopeptidase (PSE) (EC 3.4.21.26) from Flavobacterium meningosepticum was subjected to partial amino acid sequencing. According to the peptide sequences obtained, oligonucleotides were used to amplify a PSE-specific DNA fragment of 930 bp from F. meningosepticum genomic DNA, employing the polymerase chain reaction technique. This fragment served as a molecular probe to isolate the respective gene. DNA sequencing revealed that the PSE gene consists of 2118 bp coding for a 78,634 Da protein of 705 amino acids. The coding region was cloned in different expression vectors of Escherichia coli. Transformed E. coli cells overproduce an active prolyl endopeptidase of 75,000 relative molecular mass, which is delivered to the bacterial periplasmic space. Up to 1.6 units of active prolyl endopeptidase were obtained from 1 mg E. coli cells. Furthermore, the efficient purification of active prolyl endopeptidase from the periplasm of recombinant E. coli cells is described.

Design of (omega-N-(O-acyl)hydroxy amid) aminodicarboxylic acid pyrrolidides as potent inhibitors of proline-specific peptidases

A novel class of competitive, acylating inhibitors for the proline-specific peptidases: dipeptidyl peptidase IV, dipeptidyl peptidase II and prolyl endopeptidase, has been developed. The inhibitor molecules combine the efficacy of aminoacyl pyrrolidides and the potential transacylating capability of diacyl hydroxyl amines. The N-terminal deblocked inhibitors are potent reversible inhibitors of porcine kidney dipeptidyl peptidase IV, human placenta dipeptidyl peptidase II exhibiting Ki values in the microM range. Boc-protected (omega-N-hydroxy acyl amid) aminodiacarboxylic acid pyrrolidides inhibit substrate hydrolysis by prolyl endopeptidases from different sources competitively reaching Ki values of 30 nM to 60 microM. Additionally, alpha-N-BOC-(omega-N-hydroxy acetyl) glutaminyl pyrrolidide modifies human placenta prolyl endopeptidase in a time-dependent reaction.