Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We characterized a highly purified preparation of the chromosomally encoded dihydrofolate reductase (DHFR) from a trimethoprim-susceptible (Tmp8; strain MAP) and two trimethoprim-resistant (TmpR) strains (MAP/47 and MAP/42) of Haemophilus influenzae. The enzymes were purified between 650- and 3000-fold by gel-filtration and dye-ligand chromatography. The apparent molecular mass of the three proteins was 18400 Da by PAGE under denaturing and nondenaturing conditions. Total enzyme activity was greater in all fractions from the TmpR strains compared with the Tmp8 isolate. The three enzymes had a similar Km for dihydrofolate (7, 9 and 5 microM) and NADPH (2, 5 and 6 microM). However, the Tmp IC50 (the concentration necessary for 50% inhibition of DHFR activity) for the Tmp8 strain MAP was 0.001 microM, whereas DHFR from the TmpR strains MAP/47 and MAP/42 had values of 0.1 microM and 0.3 microM respectively. The methotrexate IC50 of the MAP/42 DHFR was 0.06 microM in comparison with the enzyme from MAP (0.008 microM) and MAP/47 (0.007 microM). Isoelectric focusing indicated that the DHFR from MAP/42 had a different isoelectric point (pI 7.6) compared with the enzymes from MAP and MAP/47 (pI 7.3). Peptide mapping after digestion with trypsin revealed one major peptide fragment (7.9 kDa) in the DHFR of MAP and MAP/47 and three major tryptic fragments (7.9, 9.6 and 12.5 kDa) in DHFR from MAP/42. We conclude that trimethoprim resistance in H. influenzae results from overproduction of structurally altered DHFR(s).
 ...
PMID:Trimethoprim resistance in Haemophilus influenzae is due to altered dihydrofolate reductase(s). 201 95

Proximal tubules were isolated in highly pure form from rabbit cortices by a mechanical procedure that is known to preserve the structural and metabolic aspects of the tubular cells. Postnuclear supernates prepared from the isolated tubules were subjects to isopycnic centrifugation in linear sucrose gradients. The enzyme activities associated with the plasma membrane (gamma-glutamyl transpeptidase, amino-peptidase M, alkaline phosphatase, Na-K-ATPase, and phosphodiesterase I) exhibited sharp unimodal frequency-density profiles with a median density near 1.16 g/ml, which shifted to a heavier density when treated with digitonin. The lysosomal enzymes, N-acetyl-beta-glucosaminidase, alpha-mannosidase, and cathepsin B, and the peroxisomal enzyme catalase exhibited particle-associated activity near a density of 1.22 g/ml. Disruption of these particles by freezing and thawing resulted in these activities appearing in the rho = 1.10 g/ml region of the gradient where the soluble cytosolic enzyme, phosphoglucomutase, exhibited activity. Cytochrome oxidase activity typical of mitochondria gave a sharp unimodal profile at rho = 1.18 g/ml. Microsomal glucose-6-phosphatase and NADPH: cytochrome c reductase activities gave median densities near 1.16 g/ml, which did not change after incubation with digitonin. Galactosyl transferase activity gave a skewed profile at rho = 1.16 g/ml and showed a slight shift to heavier density after digitonin. This study of the enzymatic activities and density gradient distribution of the components of the proximal tubule cells provides the methodology for the further study of the cellular processing of endogenous and exogenous substances by this vital cell type.
 ...
PMID:Analytical cell fractionation of isolated rabbit renal proximal tubules. 730 Jan 16

Chinese hamster dihydrofolate reductase (ch-DHFR) was overexpressed in Escherichia coli DH5 alpha under the transcriptional control of PRPL promoters regulated by temperature-sensitive repressors. The desired recombinant product is soluble and constitutes about 30% of the total soluble proteins of the bacterial cell. With repeated cycles of freezing and thawing as a first step, the purification of the recombinant ch-DHFR to homogeneity requires only one further step, gel filtration on a Sephadex G-75 column with 85-90% enzyme recovery, two to three times higher than that obtained with the commonly used affinity chromatography on a methotrexate-Sepharose column. The purified enzyme migrates as a single protein band on SDS-polyacrylamide gel electrophoresis with approximate mass of 23 kDa, in accord with that calculated from the DNA sequence. The initiation methionine residue at the N-terminus of the enzyme is completely removed by E. coli methionine aminopeptidase as judged by amino-terminal analysis. The steady-state kinetic parameters, dissociation constants for binary complexes of dihydrofolate, NADPH, and methotrexate with ch-DHFR, and the inhibitor constant of methotrexate have also been determined. The enzyme is activated about 4-fold in 3 M urea and about 2.5-fold in 0.5 M guanidine hydrochloride.
 ...
PMID:Soluble expression in Escherichia coli, one-step purification, and characterization of Chinese hamster dihydrofolate reductase. 905 90

PR-39, which is an endogenous antimicrobial peptide, can bind to Src homology 3 domains of the NADPH complex protein p47(phox) and the signaling adapter protein p130(Cas). Recently, we have reported that PR-39 gene transduction altered invasive activity and actin structure of human hepatocellular carcinoma cells, suggesting that this peptide affects cellular signaling due to its proline-rich motif. In order to clarify the mechanism of the PR-39 functions, we transfected the PR-39 gene into mouse NIH3T3 cells which had already been transformed with human activated k-ras gene. The PR-39 gene transfectant showed a reorganization of actin structure and suppression of cell proliferation both in vitro and in vivo. Decreases of MAP (mitogen-activated protein) kinase activity, cyclin D1 expression and JNK activity were observed in the PR-39 gene transfectant. Co-immunoprecipitation analysis revealed that PR-39 binds to PI3-kinase p85alpha, which is a regulatory subunit of PI3-kinase and one of the effectors by which ras induces cytoskeletal changes and stimulates mitogenesis. The PI3-kinase activity of the PR-39 gene transfectant was decreased compared with that of the ras transformant. These results suggest that PR-39 alters actin structure and cell proliferation rate by binding to PI3-kinase p85alpha and suppressing the PI3-kinase activity.
 ...
PMID:PI3-kinase p85alpha is a target molecule of proline-rich antimicrobial peptide to suppress proliferation of ras-transformed cells. 1157 64

Thiols like glutathione may serve as reducing cofactors in the production of nitric oxide (NO) and protect NO from inactivation by radical oxygen species. Depletion of thiol compounds reduces NO-mediated vascular effects in vitro and in vivo. The mechanisms underlying these actions are not clear, but may involve decreased synthesis of NO and/or increased degradation of NO. This study investigates the effect of glutathione depletion on the response to NO-mediated vasodilation induced by acetylcholine (Ach, 10 micrograms/kg), endothelial NO synthase (eNOS) activity and potential markers of vascular superoxide anion (O2.-) production in conscious chronically catheterized rats. Thiol depletion induced by buthionine sulfoximine (BSO, 1 g i.p. within 24 h) decreased the hypotensive effect of Ach by 30% (MAP reduction before BSO 27 +/- 3 mmHg, 19 +/- 3 mmHg after BSO, (mean +/- SEM), p < .05, n = 8). The impaired effect of Ach was associated with a significant reduction in eNOS activity (control: 7.7 +/- 0.8, BSO: 3.9 +/- 0.4 pmol/min/mg protein (p < .05), n = 6). In contrast, neither NADH/NADPH driven membrane-associated oxidases nor lucigenin reductase activity were significantly (p < .05) affected by BSO (BSO: 4415 +/- 123, control: 4105 +/- 455 counts/mg; n = 6) in rat aorta. It is concluded that in vivo thiol depletion results in endothelial dysfunction and a reduced receptor-mediated vascular relaxation. This effect is caused by reduced endothelial NO formation.
 ...
PMID:Endothelium-dependent vasorelaxation in inhibited by in vivo depletion of vascular thiol levels: role of endothelial nitric oxide synthase. 1169 35

Exogenous administration of pineal hormone melatonin (MEL) has been demonstrated to attenuate organ damage in models of I/R and inflammation by antioxidative effects. However, specific organ-protective effects of MEL with respect to hemorrhagic shock have not been investigated yet. In the present study, we evaluated the role of MEL pretreatment for hepatic perfusion, redox state, and function after hemorrhage and resuscitation, with emphasis on MEL receptor activation. In a model of hemorrhagic shock (MAP 35 +/- 5 mmHg for 90 min) and reperfusion (2 h), we measured nicotinamide adenine dinucleotide phosphate (reduced form; NADPH) autofluorescence, hepatic microcirculation, and hepatocellular injury by intravital microscopy, as well as plasma disappearance rate of indocyanine green (PDRICG) as a sensitive maker of liver function in rat. Pretreatment with 10 mg kg(-1) MEL (i.v.) 15 min before induction of hemorrhage resulted in a significantly improved PDR(ICG) compared with controls (MEL/shock, 15.02% min(-1) +/- 2.9 SD vs. vehicle/shock, 6.18 +/- 4.6 SD; P = 0.001). Intravital microscopy after reperfusion revealed an improved hepatic perfusion index, redox state, and reduced hepatocellular injury in pretreated animals compared with the vehicle group. Melatonin receptor antagonist luzindole (LZN; 2.5 mg kg(-1)) almost completely abolished the protective effects of MEL pretreatment with respect to liver function (MEL + LZN/shock PDR(ICG), 7.31% min(-1) +/- 3.4 SD). Beneficial effects regarding hepatic perfusion, redox state, and cellular injury were not influenced by LZN, indicating that they may depend on antioxidative effects of MEL. However, liver function after hemorrhage is effectively maintained by MEL pretreatment via receptor-dependent pathways.
 ...
PMID:Melatonin pretreatment improves liver function and hepatic perfusion after hemorrhagic shock. 1766 50

Activating mutations of the FMS-like tyrosine kinase-3 (FLT3) receptor occur in approximately 30% of acute myeloid leukemia (AML) patients and, at least for internal tandem duplication (ITD) mutations, are associated with poor prognosis. FLT3 mutations trigger downstream signaling pathways including RAS-MAP/AKT kinases and signal transducer and activator of transcription-5 (STAT5). We find that FLT3/ITD mutations start a cycle of genomic instability whereby increased reactive oxygen species (ROS) production leads to increased DNA double-strand breaks (DSBs) and repair errors that may explain aggressive AML in FLT3/ITD patients. Cell lines transfected with FLT3/ITD and FLT3/ITD-positive AML cell lines and primary cells demonstrate increased ROS. Increased ROS levels appear to be produced via STAT5 signaling and activation of RAC1, an essential component of ROS-producing NADPH oxidases. A direct association of RAC1-GTP binding to phosphorylated STAT5 (pSTAT5) provides a possible mechanism for ROS generation. A FLT3 inhibitor blocked increased ROS in FLT3/ITD cells resulting in decreased DSB and increased repair efficiency and fidelity. Our study suggests that the aggressiveness of the disease and poor prognosis of AML patients with FLT3/ITD mutations could be the result of increased genomic instability that is driven by higher endogenous ROS, increased DNA damage, and decreased end-joining fidelity.
 ...
PMID:Internal tandem duplication of FLT3 (FLT3/ITD) induces increased ROS production, DNA damage, and misrepair: implications for poor prognosis in AML. 1819 5

Microvascular failure is a major determinant for the development of hepatocellular dysfunction after hemorrhagic shock. Induction of heme oxygenase (HO) 1 may confer hepatocellular protection. Hemin arginate (HAR) induces HO-1 and protects against shock-induced organ failure. The mechanisms are not completely understood, but HO-1-mediated protective effects on the microcirculation and on the inflammatory response may contribute. Therefore, the aim of the present study was to investigate the influence of HAR pretreatment on liver microcirculation and cytokine response to assess the role of HO-1-mediated effects under these conditions. Male Sprague-Dawley rats (200-300 g; n=8 per group) were subjected to hemorrhage (MAP, 30-40 mmHg for 1 h) 24 h after pretreatment with vehicle (Ringer solution) or HAR (5 mg kg(-1)), followed by 2 h of resuscitation. The microcirculation and the redox state (nicotinamide adenine dinucleotide phosphate [reduced form; NADPH] autofluorescence) of the liver were assessed using intravital microscopy. Cytokine levels (TNF-alpha and IL-10) were quantified using an enzyme-linked immunosorbent assay. A profound induction of HO-1 was observed 24 h after pretreatment with HAR. Hemorrhage significantly reduced sinusoidal perfusion and increased NADPH autofluorescence and cytokine levels. Hemin arginate pretreatment significantly improved liver microcirculation, reduced NADPH autofluorescence, significantly increased IL-10, and tended to decrease TNF-alpha serum levels compared with shock vehicle. Blockade of the HO pathway with tin-mesoporphyrin-IX after HAR pretreatment abolished the observed beneficial effects, whereas the additional administration of the carbon monoxide donor dichloromethane reversed the tin-mesoporphyrin-IX-mediated changes. These results suggest that HAR pretreatment improves liver microcirculation and mediates an anti-inflammatory cytokine response after hemorrhagic shock through induction of HO-1 and in part through an increased carbon monoxide release.
 ...
PMID:Hemin arginate-induced heme oxygenase 1 expression improves liver microcirculation and mediates an anti-inflammatory cytokine response after hemorrhagic shock. 1841 32

Regulated synthesis of reactive oxygen species (ROS) by specific fungal NADPH oxidases (Noxs) plays a key role in fungal cellular differentiation and development. Fungi have up to three different Nox isoforms, NoxA, B and C. The NoxA isoform has a key role in triggering the development of fruiting bodies in several sexual species whereas NoxB plays a key role in ascospore germination. The function of NoxC remains unknown. Both NoxA and NoxB are required for the development of fungal infection structures by some plant pathogens. ROS production by NoxA is critical for maintaining a fungal-plant symbiosis. Localised synthesis of ROS is also important in establishing and maintaining polarised hyphal growth. Activation of NoxA/NoxB requires the regulatory subunit, NoxR, and the small GTPase RacA. The BemA scaffold protein may also be involved in the assembly of the Nox complex. By analogy with mammalian systems MAP and PAK kinases may regulate fungal Nox activation. How fungal cells sense and respond to ROS associated with cellular differentiations remains to be discovered.
 ...
PMID:Role of reactive oxygen species in fungal cellular differentiations. 1898 37

Until recently, the production of reactive oxygen species by NADPH oxidase has been considered only in the context of the oxidative damage to pathogens inside the phagosome. However, homologues of phagocytic NADPH oxidase have been found in almost all cell types, where they produce hydrogen peroxide and thereby regulate the initial intracellular stages of MAP kinase cascades. In the present work, the activation of two MAP kinase cascades, p38 and Erk1/2, during phagocytosis has been studied. It was found that phagocytosis activates both cascades. The activation of Erkl/2 is dependent, and the activation of p38 is not dependent, on the activity of NADPH oxidase. Thus, it can be stated that the activation of MAP kinases in phagocytes during phagocytosis occurs by a mechanism similar to that operating in nonphagocytizing cells, indicating the universality of the function of NADPH oxidases in different cell types.
 ...
PMID:[Signaling function of phagocytic NADPH oxidase: activation of MAP kinase cascades in phagocytosis]. 2038 87


1 2 Next >>