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)

Haemophilus parasuis, grown under conditions of high aeration, was found to lack a tricarboxylic acid cycle but to possess phosphoenolpyruvate carboxylase and a reductive pathway leading to the production of succinate. Such organisms contained approximately equal quantities of b-, c-, and d-type cytochromes and excreted acetate. When the oxygen supply for growth was either reduced or eliminated, the specific activities of phosphoenolpyruvate carboxylase, malate dehydrogenase, fumarase, fumarate reductase, and NADH: fumarate oxidoreductase were increased substantially, and the acid products were succinate, acetate, and formate. Organisms grown under the latter conditions also contained increased quantities of b- and c-type cytochromes, some of which were low-potential cytochromes. These low-potential cytochromes were reduced by NADH and oxidized by fumarate, and hence, appeared to be components of NADH: furmarate oxidoreductase. Our results indicate that in H. parasuis, growing aerobically in medium containing glucose, the sole function of the reductive pathway is to provide intermediates for biosynthetic processes, and oxygen is the preferred electron acceptor. As the supply of oxygen is reduced or eliminated, the reductive pathway becomes more involved in NAD+ recycling and fumarate becomes the acceptor. In effect, irrespective of the oxygen supply, the growth of H. parasuis is absolutely dependent upon the presence of an electron transport system.
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PMID:Effect of oxygen supply during growth on the production of cytochromes, enzymes, and acid end products by Haemophilus parasuis. 146 68

Previous studies of Haemophilus organisms documented the importance of an NAD+-dependent malate dehydrogenase in the incomplete tricarboxylic acid cycle present in these organisms. Selective interactions occurring at the coenzyme and substrate binding sites of a purified Haemophilus influenzae malate dehydrogenase were investigated. Coenzyme-competitive inhibition by adenosine derivatives demonstrated the presence of regions in the coenzyme binding site that interacted with the adenosine and pyrophosphate moieties of the coenzyme. Positive chainlength effects in the coenzyme-competitive inhibition by aliphatic carboxylic acids indicated the presence of a hydrophobic region at this site that was close to the pyrophosphate region. Seven analogues of NAD+ that were structurally altered in either the pyridine or purine ring were evaluated as selective inhibitors of the enzyme. The three most effective inhibitors of the purified malate dehydrogenase inhibited the growth of H. influenzae when the organism was grown on a limiting concentration of NAD+.
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PMID:Site-directed inhibition of Haemophilus influenzae malate dehydrogenase. 261 81

Rat liver d-3-phosphoglycerate dehydrogenase was purified to homogeneity and digested with trypsin, and the sequences of two peptides were determined. This sequence information was used to screen a rat hepatoma cDNA library. Among 11 positive clones, two covered the whole coding sequence. The deduced amino acid sequence (533 residues; Mr 56493) shared closer similarity with Bacillus subtilis 3-phosphoglycerate dehydrogenase than with the enzymes from Escherichia coli, Haemophilus influenzae and Saccharomyces cerevisiae. In all cases the similarity was most apparent in the substrate- and NAD+-binding domains, and low or insignificant in the C-terminal domain. A corresponding 2.1 kb mRNA was present in rat tissues including kidney, brain and testis, whatever the dietary status, and also in livers of animals fed a protein-free, carbohydrate-rich diet, but not in livers of control rats, suggesting transcriptional regulation. The full-length rat 3-phosphoglycerate dehydrogenase was expressed in E. coli and purified. The recombinant enzyme and the protein purified from liver displayed hyperbolic kinetics with respect to 3-phosphoglycerate, NAD+ and NADH, but substrate inhibition by 3-phosphohydroxypyruvate was observed; this inhibition was antagonized by salts. Similar properties were observed with a truncated form of 3-phosphoglycerate dehydrogenase lacking the C-terminal domain, indicating that the latter is not implicated in substrate inhibition or in salt effects. By contrast with the bacterial enzyme, rat 3-phosphoglycerate dehydrogenase did not catalyse the reduction of 2-oxoglutarate, indicating that this enzyme is not involved in human D- or L-hydroxyglutaric aciduria.
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PMID:Cloning, sequencing and expression of rat liver 3-phosphoglycerate dehydrogenase. 916 25

Alanine dehydrogenase (AlaDH: EC 1.4.1.1), malate dehydrogenase (MDH: EC 1.1.1.37), and glutamate dehydrogenase (EC 1.4.1.2), all NAD+ dependent, were detected in extracts from a psychrophilic bacterium, strain PA-43, isolated from a sea urchin off the Icelandic coast. Characterization tests suggested that the strain had a close relationship to Vibrio, but sequencing of part of the 16S rDNA gene placed the bacterium among Shewanella species in a constructed phylogenetic tree. The bacterium had an optimum growth temperature of 16.5 degrees C, and maximum dehydrogenase expression was obtained in a rich medium supplemented with NaCl. Both AlaDH and MDH were purified to homogeneity. AlaDH is a hexamer, with an approximate relative molecular mass of 260,000, whereas MDH is dimeric, with an apparent relative molecular mass of approximately 70,000. Both enzymes were thermolabile, and the optimum temperatures for activity were shifted toward lower temperatures than those found in the same enzymes from mesophiles, 37 degrees C for MDH and approximately 47 degrees C for AlaDH. The pH optima for AlaDH in the forward and reverse reactions were 10.5 and 9, respectively, whereas those for MDH were 10-10.2 and 8.8, respectively. Partial amino acid sequences, comprising approximately 30% of the total sequences from each enzyme, were determined for N-terminal, tryptic, and chymotryptic fragments of the enzymes. The AlaDH showed the highest similarity to AlaDHs from the psychrotroph Shewanella Ac10 and the mesophile Vibrio proteolyticus, whereas MDH was most similar to the MDHs from the mesophiles Escherichia coli and Haemophilus influenzae, with lower identity to the psychrophilic malate dehydrogenases from Vibrio 5710 and Photobacterium SS9.
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PMID:Characterization of alanine and malate dehydrogenases from a marine psychrophile strain PA-43. 1145 64

Previously, we characterized a pathway necessary for the processing of NAD+ and for uptake of nicotinamide riboside (NR) in Haemophilus influenzae. Here we report on the role of NadR, which is essential for NAD+ utilization in this organism. Different NadR variants with a deleted ribonucleotide kinase domain or with a single amino acid change were characterized in vitro and in vivo with respect to cell viability, ribonucleotide kinase activity, and NR transport. The ribonucleotide kinase mutants were viable only in a nadV+ (nicotinamide phosphoribosyltransferase) background, indicating that the ribonucleotide kinase domain is essential for cell viability in H. influenzae. Mutations located in the Walker A and B motifs and the LID region resulted in deficiencies in both NR phosphorylation and NR uptake. The ribonucleotide kinase function of NadR was found to be feedback controlled by NAD+ under in vitro conditions and by NAD+ utilization in vivo. Taken together, our data demonstrate that the NR phosphorylation step is essential for both NR uptake across the inner membrane and NAD+ synthesis and is also involved in controlling the NAD+ biosynthesis rate.
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PMID:Coupling of NAD+ biosynthesis and nicotinamide ribosyl transport: characterization of NadR ribonucleotide kinase mutants of Haemophilus influenzae. 1596 50

DNA ligases are indispensable enzymes playing a critical role in DNA replication, recombination, and repair in all living organisms. Bacterial NAD+-dependent DNA ligase (LigA) was evaluated for its potential as a broad-spectrum antibacterial target. A novel class of substituted adenosine analogs was discovered by target-based high-throughput screening (HTS), and these compounds were optimized to render them more effective and selective inhibitors of LigA. The adenosine analogs inhibited the LigA activities of Escherichia coli, Haemophilus influenzae, Mycoplasma pneumoniae, Streptococcus pneumoniae, and Staphylococcus aureus, with inhibitory activities in the nanomolar range. They were selective for bacterial NAD+-dependent DNA ligases, showing no inhibitory activity against ATP-dependent human DNA ligase 1 or bacteriophage T4 ligase. Enzyme kinetic measurements demonstrated that the compounds bind competitively with NAD+. X-ray crystallography demonstrated that the adenosine analogs bind in the AMP-binding pocket of the LigA adenylation domain. Antibacterial activity was observed against pathogenic Gram-positive and atypical bacteria, such as S. aureus, S. pneumoniae, Streptococcus pyogenes, and M. pneumoniae, as well as against Gram-negative pathogens, such as H. influenzae and Moraxella catarrhalis. The mode of action was verified using recombinant strains with altered LigA expression, an Okazaki fragment accumulation assay, and the isolation of resistant strains with ligA mutations. In vivo efficacy was demonstrated in a murine S. aureus thigh infection model and a murine S. pneumoniae lung infection model. Treatment with the adenosine analogs reduced the bacterial burden (expressed in CFU) in the corresponding infected organ tissue as much as 1,000-fold, thus validating LigA as a target for antibacterial therapy.
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PMID:Novel bacterial NAD+-dependent DNA ligase inhibitors with broad-spectrum activity and antibacterial efficacy in vivo. 2118 50