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  • Kinetic and Spectroscopic Characterization of 1Naphthol 2-hydroxylase from Pseudomonas sp. Strain C5
    Applied biochemistry and biotechnology, 2014
    Co-Authors: Vikas D. Trivedi, Prabin D. Majhi, Prashant S. Phale
    Abstract:

    1Naphthol 2-hydroxylase (1-NH) catalyzes the conversion of 1Naphthol to 1,2-dihydroxynaphthalene. 1-NH from carbaryl degrading Pseudomonas strain C5 was purified and characterized for its kinetic and spectroscopic properties. The enzyme was found to be NAD(P)H-dependent external flavin monooxygenase. Though the kinetic parameters of 1-NH from strain C5 appear to be similar to 1-NH enzyme from strains C4 and C6, however, they differ in their N-terminal sequences, mole content of flavin adenadenineudinucleotide (FAD), reconstitution of apoenzyme, and Ki. 1-NH showed narrow substrate specificity with comparable hydroxylation efficiency on 1Naphthol and 5-amino 1Naphthol (~30 %) followed by 4-chloro 1Naphthol (~9 %). Salicylate was found to be the nonsubstrate effector. The flavin fluorescence of 1-NH was found to increase in the presence of 1Naphthol (Kd = 11.3 μM) and salicylate (Kd = 1027 μM). The circular dichdichroism (CD) spectra showed significant perturbations in the presence of NAD(P)H, whereas no changes were observed in the presence of 1Naphthol. Naphthalene, 1-chloronaphthalene, 2-napthol, and 2-naphthoic acid were found to be the mixed inhibitors. Chemical modification studies showed the probable involvement of His, Cys, and Tyr in the binding of 1Naphthol, whereas Trp was found to be involved in the binding of NAD(P)H.

  • 1Naphthol 2-hydroxylase from Pseudomonas sp. strain C6: purification, characterization and chemical modification studies
    Biodegradation, 2011
    Co-Authors: Prashant S. Phale
    Abstract:

    1Naphthol 2-hydroxylase (1-NH) which catalyzes the conversion of 1Naphthol to 1,2-dihydroxynaphthalene was purified to homogeneity from carbaryl-degrading Pseudomonas sp. strain C6. The enzyme was found to be a homodimer with subunit molecular weight of 66 kDa. UV, visible and fluorescence spectral properties, identification of flavin moiety by HPLC as FAD, and reconstitution of apoenzyme by FAD suggest that enzyme is FAD-dependent. 1-NH accepts electron from NADH as well as NADPH. Besides 1Naphthol ( K _m, 9.1 μM), the enzyme also accepts 5-amino 1Naphthol ( K _m, 6.4 μM) and 4-chloro 1Naphthol ( K _m, 2.3 μM) as substrates. Enzyme showed substrate inhibition phenomenon at high concentration of 1Naphthol ( K _i, 283 μM). Stoichiometric consumption of oxygen and NADH, and biochemical properties suggest that 1-NH belongs to FAD containing external flavomonooxygenase group of oxido-reductase class of enzymes. Based on biochemical and kinetic properties, 1-NH from Pseudomonas sp. strain C6 appears to be different than that reported earlier from Pseudomonas sp. strain C4. Chemical modification and protection by 1Naphthol and NADH suggest that His, Arg, Cys, Tyr and Trp are at or near the active site of 1-NH.

  • Purification and Characterization of 1Naphthol-2-Hydroxylase from Carbaryl-Degrading Pseudomonas Strain C4
    Journal of bacteriology, 2007
    Co-Authors: Vandana P. Swetha, Aditya Basu, Prashant S. Phale
    Abstract:

    Pseudomonas sp. strain C4 metabolizes carbaryl (1-naphthyl-N-methylcarbamate) as the sole source of carbon and energy via 1Naphthol, 1,2-dihydroxynaphthalene, and gentisate. 1Naphthol-2-hydroxylase (1-NH) was purified 9.1-fold to homogeneity from Pseudomonas sp. strain C4. Gel filtfiltration and sodium dodedodecyl sulfatepolyacrylamide gel electrophoresis showed that the enzyme is a homodimer with a native molecular mass of 130 kDa and a subunit molecular mass of 66 kDa. The enzyme was yellow, with absorption maxima at 274, 375, and 445 nm, indicating a flavoprotein. High-performance liquid chrochromatography analysis of the flavin moiety extracted from 1-NH suggested the presence of flavin adenadenineudinucleotide (FAD). Based on the spectral properties and the molar extinction coefficient, it was determined that the enzyme contained 1.07 mol of FAD per mol of enzyme. Although the enzyme accepts electrons from NADH, it showed maximum activity with NADPH and had a pH optimum of 8.0. The kinetic constants Km and Vmax for 1Naphthol and NADPH were determined to be 9.6 and 34.2 μM and 9.5 and 5.1 μmol min−1 mg−1, respectively. At a higher concentration of 1Naphthol, the enzyme showed less activity, indicating substrate inhibition. The Ki for 1Naphthol was determined to be 79.8 μM. The enzyme showed maximum activity with 1Naphthol compared to 4-chloro-1Naphthol (62%) and 5-amino-1Naphthol (54%). However, it failed to act on 2-Naphthol, substituted naphthalenes, and phenol derivatives. The enzyme utilized one mole of oxygen per mole of NADPH. Thin-layer chromatographic analysis showed the conversion of 1Naphthol to 1,2-dihydroxynaphthalene under aerobic conditions, but under anaerobic conditions, the enzyme failed to hydroxylate 1Naphthol. These results suggest that 1-NH belongs to the FAD-containing external flavin mono-oxygenase group of the oxidoreductase class of proteins.

Elliot R. Bernstein – One of the best experts on this subject based on the ideXlab platform.

Seong Keun Kim – One of the best experts on this subject based on the ideXlab platform.

  • Excited state intermolecular proton transfer in isolated clusters: 1Naphthol/ammonia and water
    The Journal of Chemical Physics, 1991
    Co-Authors: Seong Keun Kim, Elliot R. Bernstein
    Abstract:

    The excited singlet state intermolecular proton transfer reaction in jet‐cooled clusters of 1Naphthol/ammonia and water is investigated employing mass resolved excitation, threshold photoionization, and emission spectroscopy. The complete data set indicates that no proton transfer occurs for 1Naphthol(NH3)1,2 and (H2O)n, n=1,…,20 clusters. Proton transfer occurs for (at least) one configuration of the 1Naphthol(NH3)3 cluster, as well as all 1Naphthol(NH3)n, n≥4, clusters. The (at least) two configurations of 1Naphthol(NH3)3 clusters are distinguished by threshold photoionization studies. The 1Naphthol(NH3)3 cluster for which proton transfer is indicated has a threshold photoionization energy ∼2000 cm−1 below the other 1Naphthol(NH3)3 cluster configurations. These results are employed to explain the previous discrepancy between static spectroscopic experiments and picosecond time resolved dynamic experiments concerning proton transfer in the 1Naphthol(NH3)3 cluster. Calculations of cluster geomet…

Ehud Pines – One of the best experts on this subject based on the ideXlab platform.

R. Knochenmuss – One of the best experts on this subject based on the ideXlab platform.

  • Photoionization, fragmentation and proton transfer in 1Naphthol(NH3)n clusters
    Chemical Physics Letters, 1999
    Co-Authors: R. Knochenmuss
    Abstract:

    Abstract The fragmentation of photoionized 1Naphthol·(NH 3 ) n clusters is examined. In one-color resonant two-photphotoniionization experiments, fragmentation in the ion state is observed for every cluster size above n =1. For small clusters ( n ≤4), a single neutral ammonia is evaporated in the ion state. This ceases at energies 1500–2500 cm −1 above the ionization thresholds. Larger clusters, n ≥5, are readily ionized at much lower energies than n ≤4. They yield (1Naphthol·(NH 3 ) n ) + , 1Naphthol·(NH 3 ) n H + , and (NH 3 ) n H + ion fragments. Several neutral ammonia molecules can be lost. These observations support predictions that n ≥5 clusters undergo proton transfer in the ground state.