Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the dapE-encoded desuccinylase is required for the bacterial synthesis of lysine and meso-diaminopimelic acid. We have investigated the catalytic mechanism of the recombinant enzyme from Haemophilus influenzae. The desuccinylase was overexpressed in Escherichia coli and purified to homogeneity. Steady-state kinetic experiments verified that the enzyme is metal-dependent, with a Km for N-succinyl-L,L-diaminopimelic acid of 1.3 mM and a turnover number of 200 s-1 in the presence of zinc. The maximal velocity was independent of pH above 7 but decreased with a slope of 1 below pH 7. The pH dependence of V/K was bell-shaped with apparent pKs of 6.5 and 8.3. Both L,L- and D,L-diaminopimelic acid were competitive inhibitors of the substrate, but d,d-diaminopimelic acid was not. Solvent kinetic isotope effect studies yielded inverse isotope effects, with values for D2OV/K of 0.62 and D2OV of 0.78. Determination of metal stoichiometry by ICP-AES indicated one tightly bound metal ion, while sequence homologies suggest the presence of two metal binding sites. On the basis of these observations, we propose a chemical mechanism for this metalloenzyme, which has a number of important structurally defined homologues.
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PMID:Hydrolysis of N-succinyl-L,L-diaminopimelic acid by the Haemophilus influenzae dapE-encoded desuccinylase: metal activation, solvent isotope effects, and kinetic mechanism. 967 18

The TyrR protein of Escherichia coli (513 amino acid residues) is the chief transcriptional regulator of a group of genes that are essential for aromatic amino acid biosynthesis and transport. The TyrR protein can function either as a repressor or as an activator. The central region of the TyrR protein (residues 207 to 425) is similar to corresponding polypeptide segments of the NtrC protein superfamily. Like the NtrC protein, TyrR has intrinsic ATPase activity. Here, we report that TyrR possesses phosphatase activity. This activity is subject to inhibition by L-tyrosine and its analogues and by ATP and ATP analogues. Zinc ion (2 mM) stimulated the phosphatase activity of the TyrR protein by a factor of 57. The phosphatase-active site of TyrR was localized to a 31-kDa domain (residues 191 to 467) of the protein. However, mutational alteration of distant amino acid residues at both the N terminus and the C terminus of TyrR altered the phosphatase activity. Haemophilus influenzae TyrR (318 amino acid residues), a protein with a high degree of sequence similarity to the C terminus of the E. coli TyrR protein, exhibited a phosphatase activity similar to that of E. coli TyrR.
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PMID:The sigma(70) transcription factor TyrR has zinc-stimulated phosphatase activity that is inhibited by ATP and tyrosine. 1064 32

Actinobacillus pleuropneumoniae causes pleuropneumonia in swine. This bacterium secretes proteases that degrade porcine hemoglobin and IgA in vitro. To further characterize A. pleuropneumoniae proteases, we constructed a genomic library expressed in Escherichia coli DH5alpha, and selected a clone that showed proteolytic activity. The recombinant plasmid carries an 800-base pair A. pleuropneumoniae gene sequence that.codes for a 24-kDa polypeptide. A 350-base pair PstI fragment from the sequence hybridized at high stringency with DNA from 12 serotypes of A. pleuropneumoniae, but not with DNA from Actinobacillus suis, Haemophilus parasuis, Pasteurella haemolytica, Pasteurella multocida A or D, or E. coli DH5alpha, thus showing specificity for A. pleuropneumoniae. The expressed polypeptide was recognized as an antigen by convalescent-phase pig sera. Furthermore, a polyclonal antiserum developed against the purified polypeptide recognized an A. pleuropneumoniae oligomeric protein in both crude-extract and cell-free culture media. This recombinant polypeptide cleaved azocoll, gelatin, and actin. Inhibition of the proteolytic activity by diethylpyrocarbonate suggests that this polypeptide is a zinc metalloprotease.
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PMID:A 24-kDa cloned zinc metalloprotease from Actinobacillus pleuropneumoniae is common to all serotypes and cleaves actin in vitro. 1080 46

We present here computer generated model of N-terminal fragment, amino acids (aa) 36-245, of a Plasmodium vivax heat shock metalloprotease called PVHSP28, whose gene was cloned and characterised earlier. The fragment showed homology with HSPs from many organisms, including Escherichia coli and Haemophilus influenzae. PVHSP28 had the signature sequence 'HEXXH' and 'EXXXD' of Zinc metalloproteases. Being the first malarial HSP possessing metalloprotease activity, PVHSP28 is an ideal target for the design of new anti-malarial drugs. However, except for a small region (aa 62-132) which had 24.6% sequence similarity with 1TAQ (a DNA polymerase), it did not show sequence similarity with any published structures in protein data bank. Hence it could not be modelled using any automated modeling programs. We modelled 36-245 aa of PVHSP28 using predicted secondary structure as well as experimentally determined and predicted properties of the protein on the basis of its amino acid sequence, using various Internet tools and in-house package MODEL. The model was energy minimised using Sander's module of AMBER 5.0, working on a Silicon Graphics machine, with all atom force field.
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PMID:Computer modeling of small heat-shock metalloprotease of the human malaria parasite Plasmodium vivax. 1169 26

The presence of active copper- and zinc-containing superoxide dismutase in isolates of the cryptic genospecies of Haemophilus, responsible for urogenital, neonatal, and mother-infant infections, can be used as a biochemical marker to discriminate them from H. influenzae sensu stricto strains.
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PMID:Active copper- and zinc-containing superoxide dismutase in the cryptic genospecies of Haemophilus causing urogenital and neonatal infections discriminates them from Haemophilus influenzae sensu stricto. 1177 29

Malnutrition, one of the world's greatest health problems, is a factor in the death of millions of children each year. Infection is the cause of death in over half these cases. Dietary deficiency, especially of protein, causes serious disturbances in the immune system. The mucus and cutaneous surfaces are the first affected. Studies of the respiratory mucus demonstrate frequent breaches which allow germs to penetrate. Antibodies are synthesized in reduced quantities, lymphocyte counts are often diminished, and reaction with infectious agents is poor. The phagocyte function of polynucleated cells is poor. Malnutrition is often associated with war, ignorance, poverty, and poor hygiene. Deficiencies of iron, vitamin A, and zinc may aggravate immune deficits. Ingestion of contaminated water is the main cause of diarrhea, which is very frequent among the malnourished and may be more serious than among adequately nourished individuals. Colibacillus and salmonella are most frequently isolated. Germs such as shigella, campylobacter, and rotavirus have the same incidence as in well nourished children. Pneumonia is responsible for 4 million deaths in children under 5 annually and is more common in the malnourished. The pathogenic agents may be pneumococci, Hemophilus, or staphylococci. Tuberculosis is also frequent, especially in zones with a prevalence of AIDS. Diagnosis of tuberculosis with cutaneous tests is difficult in the malnourished. Regardless of the pathogenic agent, pneumonia is more serious in the malnourished, and the need for treatment is more urgent. Urinary infections may occur in 10-25% of malnourished children vs. 2% of healthy children. The colibacillus is the most frequent cause. Specticemias, the most severe of infections, are not rare in the malnourished and are usually caused by Salmonella or the colibacillus. 20% of malnourished children are affected by infections acquired in the hospital. Among viral infections affecting them are measles and herpes. The fatality rate from measles may reach 25% in malnourished children. Parasitoses are frequent, but they do not seem to be more serious in malnourished children than in the general population. It is imperative in treating malnourished children to observe rigorous hygiene, use clean water, treat infections early, avoid hospital infections, and apply all available vaccines.
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PMID:[Infections in malnourished infants and children]. 1228 6

Children with sickle cell anemia are more exposed to infection than healthy children. Indeed, infections are the major cause of morbidity and mortality in children with sickle cell anemia, especially those aged 6 months to 5 years. Phagocytosis is reduced in these children. Polynuclear neutrophils reveal various poorly understood irregularities and are associated with a reduction of phagocytic power: zinc deficiency, reduced post-phagocytic oxidative metabolism, and a prevalence of neutrophils not forming red sheep-like globule carriers of immunoglobulin H. The power of the antibody which renders germs susceptible to phagocytosis in the serum is reduced in sickle cell patients. This may be tied to a disorder in the alternate complementary route with reduction of C3 and properdin. Sequestration of sickle cell-shaped red blood cells, splenic congestion, and short circuits of important functional territories contribute to spleen dysfunction, which occurs early. Common pathogens attacking sickle cell patients are pneumococci, salmonella species, and Haemophilus influenzae. They cause very grave infections (e.g., septicemia and purulent meningitis). Prevention of infections dwells on three perspectives: early screening for sickle cell anemia and for spleen dysfunction, preventive penicillin therapy, and vaccination. In Benin, vaccination is the only means to prevent infections. Essential vaccinations for children with sickle cell anemia include BCG, diphtheria-pertussis-tetanus, polio, and Rouvax. Strongly recommended vaccinations are Pneumovax 23, HEVAC B, TAB, vaccine against H. influenzae, and vaccine against mumps. A vaccine calendar for children with sickle cell anemia guides health workers when they must administer the vaccines and their boosters over a six year period. It is not yet universal in health facilities in Benin. A short- and long-term evaluation of the calendar's efficacy would allow one to appreciate its real impact on reducing morbidity and mortality in children with sickle cell anemia.
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PMID:[Prevention of infectious diseases in the drepanocytic child]. 1229 Jan 82

The catalytic and structural properties of divalent metal ion cofactor binding sites in the dapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae were investigated. Co(II)-substituted DapE enzyme was 25% more active than the Zn(II)-loaded form of the enzyme. Interestingly, Mn(II) can activate DapE, but only to approximately 20% of the Zn(II)-loaded enzyme. The order of the observed k(cat) values are Co(II) > Zn(II) > Cd(II) > Mn(II) >Ni(II) approximately equal Cu(II) approximately equal Mg(II). DapE was shown to only hydrolyze L,L-N-succinyl-diaminopimelic acid (L,L-SDAP) and was inactive toward D,L-, L,D-, and D,D-SDAP. DapE was also inactive toward several acetylated amino acids as well as D,L-succinyl aminopimelate, which differs from the natural substrate, L,L-SDAP, by the absence of the amine group on the amino acid side chain. These data imply that the carboxylate of the succinyl moiety and the amine form important interactions with the active site of DapE. The affinity of DapE for one versus two Zn(II) ions differs by nearly 2.2 x 10(3) times (K(d1) = 0.14 microM vs K(d2) = 300 microM). In addition, an Arrhenius plot was constructed from k(cat) values measured between 16 and 35 degrees C and was linear over this temperature range. The activation energy for [ZnZn(DapE)] was found to be 31 kJ/mol with the remaining thermodynamic parameters calculated at 25 degrees C being DeltaG(++) = 64 kJ/mol, DeltaH(++) = 28.5 kJ/mol, and DeltaS(++) = -119 J mol(-1) K(-1). Electronic absorption and EPR spectra of [Co_(DapE)] and [CoCo(DapE)] indicate that the first Co(II) binding site is five-coordinate, while the second site is octahedral. In addition, any spin-spin interaction between the two Co(II) ions in [CoCo(DapE)] is very weak. The kinetic and spectroscopic data presented herein suggest that the DapE from H. influenzae has similar divalent metal binding properties to the aminopeptidase from Aeromonas proteolytica (AAP), and the observed divalent metal ion binding properties are discussed with respect to their catalytic roles in SDAP hydrolysis.
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PMID:Substrate specificity, metal binding properties, and spectroscopic characterization of the DapE-encoded N-succinyl-L,L-diaminopimelic acid desuccinylase from Haemophilus influenzae. 1296

SecB is a bacterial chaperone involved in directing pre-protein to the translocation pathway by its specific interaction with the peripheral membrane ATPase SecA. The SecB-binding site on SecA is located at its C terminus and consists of a stretch of highly conserved residues. The crystal structure of SecB in complex with the C-terminal 27 amino acids of SecA from Haemophilus influenzae shows that the SecA peptide is structured as a CCCH zinc-binding motif. One SecB tetramer is bound by two SecA peptides, and the interface involves primarily salt bridges and hydrogen bonding interactions. The structure explains the importance of the zinc-binding motif and conserved residues at the C terminus of SecA in its high-affinity binding with SecB. It also suggests a model of SecB-SecA interaction and its implication for the mechanism of pre-protein transfer in bacterial protein translocation.
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PMID:Structural determinants of SecB recognition by SecA in bacterial protein translocation. 1451 49

The Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra, of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae have been recorded in the presence of one or two equivalents of Zn(II) (i.e. [Zn_(DapE)] and [ZnZn(DapE)]). The Fourier transforms of the Zn EXAFS are dominated by a peak at ca. 2.0 A, which can be fit for both [Zn_(DapE)] and [ZnZn(DapE)], assuming ca. 5 (N,O) scatterers at 1.96 and 1.98 A, respectively. A second-shell feature at ca. 3.34 A appears in the [ZnZn(DapE)] EXAFS spectrum but is significantly diminished in [Zn_(DapE)]. These data show that DapE contains a dinuclear Zn(II) active site. Since no X-ray crystallographic data are available for any DapE enzyme, these data provide the first glimpse at the active site of DapE enzymes. In addition, the EXAFS data for DapE incubated with two competitive inhibitors, 2-carboxyethylphosphonic acid and 5-mercaptopentanoic acid, are also presented.
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PMID:The dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase from Haemophilus influenzae is a dinuclear metallohydrolase. 1464 Jun 10


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