Purification and characterization of glycylprolyl aminopeptidase from Bacteroides gingivalis

Molecular mechanism for connective tissue destruction by dipeptidyl aminopeptidase IV produced by the periodontal pathogen Porphyromonas gingivalis

Porphyromonas gingivalis is a pathogen associated with adult periodontitis. It produces dipeptidyl aminopeptidase IV (DPPIV), which may act as a virulence factor by contributing to the degradation of connective tissue. We investigated the molecular mechanism by which DPPIV contributes to the destruction of connective tissue. DPPIV itself did not show gelatinase or collagenase activity toward human type I collagen, but it promoted the activity of the host-derived matrix metalloproteinase 2 (MMP-2) (gelatinase) and MMP-1 (collagenase). DPPIV bound to fibronectin and mediated the adhesion of P. gingivalis to fibronectin. Mutant DPPIV with catalytic Ser mutagenized to Ala (DPPSA) did not accelerate the degradation of collagen and gelatin by MMPs but retained fibronectin-binding activity. The adhesion of human gingival fibroblasts and NIH 3T3 cells to fibronectin was inhibited by DPPIV. Strain 4351ADPPSA exhibited an intermediate level of virulence in mice, between that of the strain expressing wild-type DPPIV (4351ADPP) and that of the strain harboring only the plasmid vector (4351AVEC). It is suggested that both activity promoting the degradation of collagen and gelatin and binding to fibronectin are required for full virulence. These results reveal novel biological functions of DPPIV and suggest a pathological role in the progression of periodontitis.

Peptidase activity of dipeptidyl aminopeptidase IV produced by Porphyromonas gingivalis is important but not sufficient for virulence

Porphyromonas gingivalis is a pathogen associated with adult periodontitis, which is a chronic inflammatory disease characterized by breakdown of the periodontal tissue. Dipeptidyl aminopeptidase IV (DPPIV) produced by P. gingivalis has been considered to be a potential virulence factor based on the finding that the virulence was reduced by disruption of the gene (dpp ) coding for DPPIV. In the present study, we constructed a shuttle vector that is mobilized from Escherichia coli to P. gingivalis and is maintained stably in both bacteria, and we showed that the virulence was restored by introducing the cloned wild-type dpp gene into the null mutant of P. gingivalis using our vector system. To assess the implications of the peptidase activity in the virulence, mutant DPPIV with the catalytic Ser mutagenized to Ala (DPPSA) was produced. The P. gingivalis strain expressing DPPSA exhibited an intermediate virulence between the strain expressing wild-type DPPIV and the strain harboring a vector. From these results, it is suggested that peptidase activity is very important but not sufficient for virulence.

Production of monoclonal antibody inhibiting dipeptidylaminopeptidase IV activity of Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative anaerobic bacterial species implicated as an important pathogen in the development of adult periodontitis. We previously cloned a gene encoding dipeptydilaminopeptidase IV (DAPIV) from P. gingivalis. In the present study, for immunological diagnosis and development of passive immunization, we produced a mouse monoclonal antibody (MAb) capable of inhibiting the DAPIV activity of P. gingivalis using highly purified recombinant DAPIV as an immunogen. The constructed MAb, designated as MAb-Pg-DAP-1, significantly inhibited DAPIV activity in P. gingivalis, as well as slightly inhibited that in other gram-negative bacteria such as Porphyromonas endodontalis and Prevotella loesheii, whereas no inhibition was seen in the gram-positive bacteria Streptococcus mutans and Actinomyces viscosus. Furthermore, the MAb did not inhibit DAPIV enzyme activity in human serum. This novel MAb may be useful for the development of immunological diagnosis capability and in passive immunization.

Purification and partial characterization of a dipeptidyl peptidase from Prevotella intermedia

A peptidase hydrolyzed X-Pro-p-nitroanilide was purified from the cell extract of Prevotella intermedia ATCC 25611 by ion-exchange chromatography and hydrophobic interaction chromatography. The purified enzyme exhibited a molecular size of 74 kDa from sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the maximum enzyme activity was found between pH 7.0 and pH 7.5. This peptidase was a serine enzyme and hydrolyzed Lys-Pro-p-nitroanilide, Arg-Pro-p-nitroanilide, and Ala-Pro-p-nitroanilide, but Lys-Ala-p-nitroanilide was not split. The enzyme may be classified as a dipeptidyl peptidase IV.

Dipeptidyl peptidase with strict substrate specificity of an anaerobic periodontopathogen Porphyromonas gingivalis

A dipeptidyl peptidase which hydrolyzed Xaa-Ala-p-nitroanilide was purified to homogeneity by sequential procedures including ammonium sulfate precipitation, ion-exchange chromatography, hydrophobic interaction chromatography, gel filtration and isoelectric focusing from the cell extract of Porphyromonas gingivalis. The purified enzyme hydrolyzed p-nitroanilide derivatives of Lys-Ala, Ala-Ala, and Val-Ala, but not Xaa-Pro. Enzyme activity was maximum at neutral pHs. Its molecular mass was 64 kDa with an isoelectric point of 5.7. The enzyme belonged to the family of serine peptidases.

Isolation and characterisation of dipeptidyl peptidase IV from Prevotella loescheii ATCC 15930

A proline-specific dipeptidyl aminopeptidase, dipeptidyl peptidase IV (EC 3.4.14.5), was purified from a cell sonicate soluble fraction of Prevotella loescheii ATCC 15930 by sequential column chromatography. The molecular mass of the native enzyme was estimated as 160 kDa by high-pressure liquid gel filtration column chromatography and unheated sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The subunit molecular mass was 80 kDa when the enzyme was heated to 100 degrees C in the presence of 2-mercaptoethanol before SDS-PAGE, suggesting that the native enzyme consists of two identical subunits and is folded in 2% SDS. The optimum pH, with glycyl-prolyl-4-methyl-coumaryl-7-amide as the substrate, was 8.0; the isoelectric point was 5.2. Purified enzyme showed a strong preference for dipeptide substrates containing proline and, less efficiently, alanine in the P1 position. The enzyme was markedly inhibited by Cd(2+), Zn(2+), Hg(2+), Co(2+), and serine proteinase inhibitor di-isopropylfluorophosphate.

Enzymatic properties of dipeptidyl aminopeptidase IV produced by the periodontal pathogen Porphyromonas gingivalis and its participation in virulence

Porphyromonas gingivalis is a major pathogen associated with adult periodontitis. We cloned and sequenced the gene (dpp) coding for dipeptidyl aminopeptidase IV (DPPIV) from P. gingivalis W83, based on the amino acid sequences of peptide fragments derived from purified DPPIV. An Escherichia coli strain overproducing P. gingivalis DPPIV was constructed. The enzymatic properties of recombinant DPPIV purified from the overproducer were similar to those of DPPIV isolated from P. gingivalis. The three amino acid residues Ser, Asp, and His, which are thought to form a catalytic triad in the C-terminal catalytic domain of eukaryotic DPPIV, are conserved in P. gingivalis DPPIV. When each of the corresponding residues of the enzyme was substituted with Ala by site-directed mutagenesis, DPPIV activity significantly decreased, suggesting that these three residues of P. gingivalis DPPIV are involved in the catalytic reaction. DPPIV-deficient mutants of P. gingivalis were constructed and subjected to animal experiments. Mice injected with the wild-type strain developed abscesses to a greater extent and died more frequently than those challenged with mutant strains. Mice injected with the mutants exhibited faster recovery from the infection, as assessed by weight gain and the rate of lesion healing. This decreased virulence of mutants compared with the parent strain suggests that DPPIV is a potential virulence factor of P. gingivalis and may play important roles in the pathogenesis of adult periodontitis induced by the organism.

Sequence analysis of the Porphyromonas gingivalis dipeptidyl peptidase IV gene

We previously constructed a Porphyromonas gingivalis genomic library and isolated the 2.9 kb EcoRV fragment which specified glycylprolyl dipeptidyl aminopeptidase (GPase). Nucleotide sequencing of this fragment identified the single 2169 bp open reading frame which coded for a 723 amino acid protein. The amino acid sequencing of the NH2-terminal domain of the native and recombinant mature enzymes suggested that the protease possessed a 16 amino acid residue signal peptide. The calculated mass of the precursor and mature proteases were 82,018 and 80,235 daltons, respectively. The homology search of this enzyme in registered protein sequences revealed that this enzyme was homologous to dipeptidyl peptidase (DPP) IV from the Flavobacterium meningosepticum and that from eukaryotic cells, including the human, mouse, and rat. Three amino acid residues, Ser-593, Asp-668, and His-700, were identified as a putative catalytic triad, a common feature of eukaryotic serine proteases. In addition, this enzyme showed a broad proteolytic spectrum toward synthetic substrates capable of splitting not only Gly-Pro-derivative but also Ala-Pro, Lys-Pro, and Phe-Pro-derivatives. Therefore, we conclude that this enzyme belongs to DPP IV rather than GPase.

Biochemical characterization of the arginine-specific proteases of Porphyromonas gingivalis W50 suggests a common precursor

Extracellular proteases of Porphyromonas gingivalis specific for arginyl peptide bonds are considered to be important virulence factors in periodontal disease. In order to determine the number, inter-relationship and kinetic properties of these proteases, extracellular enzymes with this peptide-bond specificity were purified and characterized from P. gingivalis W50. Three forms, which we denote RI, RI-A and RI-B, accounted for all of the activity in the supernatant. All three enzymes contain an alpha chain of approximately 54 kDa with the same N-terminal amino acid sequence. RI is a heterodimer of non-covalently linked alpha and beta chains which migrate to the same position on SDS/PAGE but which can be resolved by 8 M urea/PAGE. RI-A and RI-B are both monomeric, but the molecular mass of RI-B (70-80 kDa) is significantly increased due to post-translational modification with lipopolysaccharide. All forms show absolute specificity for peptide bonds with Arg in the P1 position and are also capable of hydrolysing N-terminal Arg and C-terminal Arg-Arg peptide bonds. Thus they show limited amino- and carboxy-peptidase activity. For the hydrolysis of Nalpha-benzoyl-L-Arg-p-nitroanilide, the pH optimum is 8.0 at 30 degrees C. The Vmax for all three enzymes is controlled by ionization of two residues with apparent pKas at 30 degrees C of 6. 5+/-0.05 and 9.7+/-0.05, and DeltaH values of approximately 29 kJ/mol and approximately 24 kJ/mol in the enzyme-substrate complex. By analogy with papain, the pKa of 6.5 could be ascribed to a Cys and the pKa of 9.7 to a His residue. E-64 [L-trans-epoxysuccinyl-leucylamide-4-(4-guanidino)butane] is a competitive inhibitor of RI, RI-A and RI-B. Based on physical properties and kinetic behaviour, RI-A appears to be analogous to gingipain from P. gingivalis HG66. However the alpha/beta structure of RI differs significantly from that of the high-molecular-mass multimeric complex of gingipain containing four haemagglutinins described by others. Since the genes for RI and high-molecular-mass gingipain are identical, the data indicate that an alternative processing pathway is involved in the formation of RI from the initial precursor. Furthermore, the identical N-termini and enzymic properties of the catalytic component of RI, RI-A and RI-B suggest that the maturation pathway of the RI precursor may also give rise to RI-A and RI-B. The physiological functions of these isoforms and their role in the disease process may become more apparent through examination of their interactions with host proteins.

Purification and characterization of Porphyromonas gingivalis outer membrane antigens

Porphyromonas gingivalis is strongly associated with periodontal disease. Significant titres of specific IgG antibodies to P. gingivalis can be found in healthy individuals and those with periodontitis. In this study, 22 outer membrane antigens ranging from 15.5 to 107.6 kDa were recognized by sera from persons with periodontitis and controls. Serum from individuals with periodontitis showed a significantly higher IgG response to a 31.4-kDa antigen (p < 0.05); serum from those with gingivitis demonstrated a significantly higher response to a 15.5-kDa antigen (p < 0.05). The response to the 15.5-kDa antigen might represent a protective immune response while that to the 31.4-kDa could serve as a marker for disease susceptibility. These two antigens were purified to homogeneity and their N-terminal amino acid sequences determined. The sequences did not correspond to any previously described P. gingivalis antigens. The role of these two antigens in the pathogenesis of periodontal disease remains to be determined.

Comparative study of four proteases from spent culture media of Porphyromonas gingivalis (FAY-19M-1)

Four gelatin cleaving proteases were partially purified from culture media of Porphyromonas gingivalis (FAY-19M-1) by sequential chromatography on columns of DEAE-Sepharose, Sephadex G-100 and chromatofocusing on PBE-94. The molecular mass of each of these proteases, estimated by relative mobility on gelatin-containing SDS-PAGE, was 50 kDa (Pool D1b), 120 kDa (Pool E1a), approximately 160 kDa (Pool E1b) and > 300 kDa (Pool A1a), respectively. These proteases also differed with respect to charge characteristics, inhibition profile and cleavage specificity. Protease pools A1a and E1a were inhibited by thiol modifying reagents. Protease pool A1a was also inhibited by N-tosyl-L-lysine chloromethyl ketone, and E1a was inhibited by antipain. Protease pool D1b was inhibited by E-64, leupeptin and antipain, and protease E1b was not inhibited by either of these inhibitors. The detailed substrate specificity of these proteases was checked by using chromogenic substrates, synthetic peptides and native proteins. Protease E1b was very active in degrading collagen, fibrinogen, fibronectin, IgG, IgA, third component of complement (C3), serum albumin, transferrin and varies; is directly proportional to 1-acid glycoprotein as substrates. Fibrinogen, fibronectin and complement C3 component were also cleaved by A1a, D1b and E1a. Synthetic peptides insulin B chain, cecropin P-1 and magainin were cleaved by E1b. Based on FAB analysis E1b showed preferential cleavage at hydrophobic or neutral residues. Protease A1a was active towards chromogenic substrates with either lys or arg in P1 position. Protease D1b cleaved chromogenic substrates with arg in P1 position and cleaved synthetic peptides magainin and (KIAGKIA)3-NH2 at lys residues also. Protease E1a showed glycyl-prolyl peptidase activity.

Tetracyclines inhibit Porphyromonas gingivalis-induced alveolar bone loss in rats by a non-antimicrobial mechanism

Tetracyclines have been widely used as adjuncts in periodontal therapy due to the antimicrobial efficacy of these drugs. Recently, their ability to inhibit host-derived matrix metalloproteinases (collagenase and gelatinase) and bone resorption in organ culture has also been invoked as a therapeutic rationale. The current study was undertaken to determine whether tetracyclines can inhibit alveolar bone loss in vivo due to a non-antimicrobial action of these drugs. Experimental periodontitis was induced by inoculating adult, male Sprague-Dawley rats with P. gingivalis (strain 381) following kanamycin/ampicillin pretreatment. Doxycycline, non-antimicrobial chemically-modified tetracycline (CMT-1) and vehicle alone were administered daily to 3 infected groups of rats (n = 6 rats per group; each group housed in a sterilized inflatable isolator) beginning 10 days after P. gingivalis inoculation. The control group (n = 6; non-infected rats) received only vehicle. After 5 weeks of daily drug administration by gastric intubation, the experiment was terminated and blood samples were taken from each animal to determine antibody levels against P. gingivalis. Plaque samples were collected from each group of animals before and after P. gingivalis inoculation and at the end of the experiment for microbiological examination. The jaws were removed from each rat, defleshed and then analyzed morphometrically and radiographically to assess bone loss. Serum antibody levels against P. gingivalis were significantly elevated in the 3 infected groups compared to the non-infected controls. This, together with the microbiologic findings, indicated that these groups of rats were infected with P. gingivalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning of the gene encoding a glycylprolyl aminopeptidase from Porphyromonas gingivalis

A genomic library of Porphyromonas gingivalis 381 was constructed in the cosmid vector pHC79. A clone, pSN1, was identified by the expression of glycylprolyl-naphthylamide hydrolysing activity. The DNA insert contained within the cosmid pSN1 was subcloned into the plasmid vector pBR328 to create the recombinant plasmid pSN11 containing a 2.9 kb EcoRV insert. An Escherichia coli transformant containing pSN11 produced a protein having a molecular weight of 75 kDa. Southern-blot hybridization revealed that the 2.9 kb EcoRV DNA hybridized with an identical sized Eco RV DNA fragment in the chromosomal DNA of P. gingivalis 381.