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Christopher Anthony - One of the best experts on this subject based on the ideXlab platform.

  • The structure and mechanism of Methanol Dehydrogenase
    Biochimica et Biophysica Acta, 2003
    Co-Authors: Christopher Anthony, P.a. Williams
    Abstract:

    This is a review of recent work on Methanol Dehydrogenase (MDH), a pyrroloquinoline quinone (PQQ)-containing enzyme catalysing the oxidation of Methanol to formaldehyde in methylotrophic bacteria. Although it is the most extensively studied of this class of Dehydrogenases, it is only recently that there has been any consensus about its mechanism. This is partly due to recent structural studies on normal and mutant enzymes and partly due to more definitive work on the mechanism of related alcohol and glucose Dehydrogenases. This work has also led to conclusions about the subsequent path of electrons and protons during the reoxidation of the reduced quinol form of the prosthetic group.

  • Methanol Dehydrogenase, a PQQ-containing quinoprotein Dehydrogenase.
    Sub-cellular biochemistry, 2000
    Co-Authors: Christopher Anthony
    Abstract:

    Methanol Dehydrogenase (MDH; EC 1.1.99.8) catalyses the oxidation of Methanol to formaldehyde in the periplasm of methylotrophic bacteria during growth on Methanol or methane. It was first described in Methylobacterium extorquens (Anthony and Zatman, 1964a,b) and has subsequently been shown to be the one feature that is common to almost all methylotrophs in which it often constitutes up to 15% of their soluble protein (see Anthony, 1986 for a review of the basic enzymology of a wide range of MDHs). MDH is a soluble quinoprotein which has pyrroloquinoline quinone (PQQ) as its prosthetic group and it uses a specific cytochrome, cytochrome cL as electron acceptor. It is usually assayed in a dye-linked system at high pH when ammonia is required as activator. It has an α2β2 structure; each α

  • The biochemistry of Methanol Dehydrogenase
    Microbial Growth on C1 Compounds, 1996
    Co-Authors: Christopher Anthony, Simon L. Dales
    Abstract:

    Methanol Dehydrogenase (MDH) is responsible for oxidation of Methanol to formaldehyde in almost all bacteria growing aerobically on methane or Methanol; it is a periplasmic quinoprotein which passes its electrons to a specific c-type cytochrome which is usually called cytochrome c L (Anthony, 1986, 1992, 1993, Goodwin and Anthony, 1995). Our understanding of this enzyme has increased dramatically in the last 3 years with publication of the 3-dimensional structures of the enzyme from Methylotrophus W3A1 (at 2.6 A) (Xia et al., 1992; White et al., 1993) and from Methylobacterium extorquens (at 1.94A) (Anthony et al., 1994; Ghosh et al., 1995). The system considered in this brief review will be the MDH and cytochrome c L from M. extorquens; in particular, the following questions will be considered: what does the structure tell us about the mechanisms of Methanol oxidation, and electron transfer between the two proteins, and the initial interaction (‘docking’) between MDH and cytochrome c L.

  • The interaction of Methanol Dehydrogenase and its cytochrome electron acceptor.
    Biochemical Journal, 1995
    Co-Authors: Simon L. Dales, Christopher Anthony
    Abstract:

    A fluorescence method is described for direct measurement of the interaction between Methanol Dehydrogenase (MDH) and its electron acceptor cytochrome cL. This has permitted a distinction to be made between factors affecting electron transfer and those affecting the initial binding or docking process. It was confirmed that the initial interaction is electrostatic, but previous conclusions with respect to the mechanism of EDTA inhibition have been modified. It is proposed that the initial 'docking' of MDH and cytochrome cL is by way of ionic interactions between lysyl residues on its surface and carboxylate groups on the surface of cytochrome cL. This interaction is not inhibited by EDTA, which we suggest acts by binding to nearby lysyl residues, thus preventing movement of the 'docked' cytochrome to its optimal position for electron transfer, which probably involves interaction with the hydrophobic funnel in the surface of MDH.

  • The structure of the quinoprotein alcohol Dehydrogenase of Acetobacter aceti modelled on that of Methanol Dehydrogenase from Methylobacterium extorquens.
    Biochemical Journal, 1995
    Co-Authors: G E Cozier, I G Giles, Christopher Anthony
    Abstract:

    The 1.94 A structure of Methanol Dehydrogenase has been used to provide a model structure for part of a membrane quinohaemoprotein alcohol Dehydrogenase. The basic superbarrel structure and the active-site region are retained, indicating essentially similar mechanisms of action, but there are considerable differences in the external loops, particularly those involved in formation of the shallow funnel leading to the active site.

Victor L. Davidson - One of the best experts on this subject based on the ideXlab platform.

  • Pyrroloquinoline quinone (PQQ) from Methanol Dehydrogenase and tryptophan tryptophylquinone (TTQ) from methylamine Dehydrogenase.
    Advances in Protein Chemistry, 2004
    Co-Authors: Victor L. Davidson
    Abstract:

    Publisher Summary This chapter focuses on two well-characterized representative members of each class of these enzymes, the Pyrroloquinoline quinine (PQQ)-dependent Methanol Dehydrogenase (MEDH) and the tryptophan tryptophylquinone (TTQ)-dependent methylamine Dehydrogenase (MADH). The chemical reaction mechanisms for catalysis by PQQ- and TTQ dependent enzymes are very similar to those used by other enzymes that possess carbonyl cofactors, such as pyridoxal phosphate-, topaquinone-, and pyruvoyl-dependent enzymes. The studies on these two classes of enzymes are facilitating a great deal of learning about mechanisms of carbonyl catalysis by enzymes, mechanisms of longrange interprotein electron transfer, and mechanisms of protein biosynthesis and posttranslational modification. PQQ and TTQ enzymes have an interesting common mechanistic feature of coupling active-site chemistry to surface-mediated electron transfer reactions. With the recent determinations of high-resolution crystal structures of more enzymes, and the development of systems for expression and site-directed mutagenesis of these enzymes, further insight into these fundamental biochemical processes is anticipated.

  • Ammonium ion requirement and stability of Methanol Dehydrogenase TTF·TCNQ electrodes
    The Analyst, 1996
    Co-Authors: M. G. Loughran, Victor L. Davidson, Jennifer M. Hall, Anthony Turner
    Abstract:

    The ammonium ion requirement and stability of quinoprotein Methanol Dehydrogenases were investigated with a view to incorporating them in enzyme electrodes for alcohol. This involved consideration of the effect of temperature and polyelectrolytes on enzyme stability. A packed cavity electrode was constructed using the organic conducting salt TTF·TCNQ (tetrathiafulvalene–tetracyanoquinodimethane). Methanol Dehydrogenase isolated from Paracoccus denitrificans was more stable than the enzyme isolated from Methylophilus methylotrophus and was successfully used for repeated assay in packed cavity electrodes without significant loss in current output. These investigations also showed that, contrary to suggestions in the literature, ammonium ions are necessary for efficient re-oxidation of Methanol Dehydrogenase at the organic conducting salt electrode.

  • ionic strength dependence of the reaction between Methanol Dehydrogenase and cytochrome c 551i evidence of conformationally coupled electron transfer
    Biochemistry, 1994
    Co-Authors: Thomas K. Harris, Z.-x. Xia, Victor L. Davidson, Longyin Chen, F S Mathews
    Abstract:

    The quinoprotein Methanol Dehydrogenase and cytochrome c-551i are two soluble acidic proteins that form a physiological complex in which electrons are transferred from pyrroloquinoline quinone to heme. The oxidation of Methanol Dehydrogenase by the cytochrome was studied as a function of ionic strength using stopped-flow spectroscopy. The dissociation constant (Kd) for complex formation decreased 2-fold with increasing ionic strength from 0.21 to 1.3 M and increased at higher ionic strengths. The rate constant for the electron transfer reaction (kET) increased 2-fold with increasing ionic strength from 0.21 to 1.3 M and decreased at higher ionic strengths. The variation of Kd and kET over this range of ionic strengths was described by Van Leeuwen theory, which takes into account monopole-dipole and dipole-dipole forces, in addition to the monopole-monopole force, to predict the interactions between large molecules. Analysis of the kinetic results in terms of these electrostatic interactions indicated the probable orientations for protein-protein binding and electron transfer. To explain the ionic strength dependence of the observed kET, a model is presented in which the true kET is reduced by a factor Kc, an equilibrium constant that describes some rearrangement of the proteins after a nonoptimal collision to produce the most efficient orientation for electron transfer. This model is consistent with the notion that the large reorganizational energy obtained from temperature-dependence studies of this electron transfer reaction [Harris, T. K., & Davidson, V. L. (1993) Biochemistry 32, 14145-14150] is due to such an intracomplex rearrangement.(ABSTRACT TRUNCATED AT 250 WORDS)

  • Binding and electron transfer reactions between Methanol Dehydrogenase and its physiologic electron acceptor cytochrome c-551i: a kinetic and thermodynamic analysis.
    Biochemistry, 1993
    Co-Authors: Thomas K. Harris, Victor L. Davidson
    Abstract:

    The quinoprotein Methanol Dehydrogenase and cytochrome c-551i form a physiologic complex in which electrons are transferred from pyrroloquinoline quinone to heme. The reoxidation of Methanol Dehydrogenase by the cytochrome was studied by stopped-flow spectroscopy. The rate constant for the electron transfer reaction and the dissociation constant for complex formation were each determined at temperatures ranging from 20 to 50 degrees C. The electron transfer rates varied from 1.4 to 4.6 s-1. Analysis of the electron transfer reaction by Marcus theory yielded values of 1.9 eV for the reorganizational energy and 0.071 cm-1 for the electronic coupling and predicted a theoretical distance between redox centers of 15 A. Kinetically determined dissociation constants correlated well with a Kd of 375 microM which was determined in a direct ultrafiltration binding assay. Thermodynamic analysis of the dissociation constants indicated the importance of the hydrophobic effect in complex formation.

  • The active site structure of the calcium-containing quinoprotein Methanol Dehydrogenase
    Biochemistry, 1993
    Co-Authors: S. A. White, Z.-x. Xia, W.-w. Dai, G. D. Boyd, F. S. Mathews, Yue-fan Zhang, Victor L. Davidson
    Abstract:

    Pyrroloquinoline quinone (PQQ), widely found in nature, serves as the redox cofactor in bacterial Methanol Dehydrogenase (MEDH), a heterotetrameric enzyme that oxidizes Methanol to formaldehyde. The refined structure of MEDH at 2.4-A resolution, based on recently obtained amino acid sequence data, reveals that the PQQ, located in a central channel of the disk-shaped protein, is sandwiched between a Trp side chain and a very unusual vicinal disulfide. A Ca 2+ ion forms a bridge between PQQ and the protein molecule, very close to a putative substrate binding pocket. The vicinal disulfide may form during PQQ incorporation and possibly act to hold the latter in place

Z.-x. Xia - One of the best experts on this subject based on the ideXlab platform.

  • The enzymatic reaction-induced configuration change of the prosthetic group PQQ of Methanol Dehydrogenase
    Biochemical and biophysical research communications, 2011
    Co-Authors: Jian-hua Gan, F. S. Mathews, Z.-x. Xia
    Abstract:

    Methanol Dehydrogenase is a heterotetrameric enzyme containing the prosthetic group pyrroloquinoline quinone (PQQ), which catalyzes the oxidation of Methanol to formaldehyde. The crystal structure of Methanol Dehydrogenase from Methylophilus W3A1, previously determined at high resolution, exhibits a non-planar configuration of the PQQ ring system and lends support for a hydride transfer mechanism of the enzymatic reaction catalyzed by the enzyme. To investigate why PQQ is in the C5-reduced form and to better understand the catalytic mechanism of the enzyme, three structures of this enzyme in a new crystal form have been determined at higher resolution. Two of the three crystals were grown in the presence of 1 and 50 mM Methanol, respectively, both structures of which show non-planar configurations of the PQQ ring system, confirming the previous conclusion; the other was crystallized in the presence of 50 mM ethanol, the structure of which displays a planar ring system for PQQ. Comparison of these structures reveals that the configuration change of PQQ is induced by the enzymatic reaction. The reaction takes place and the C5-reduced PQQ intermediate is produced when the enzyme co-crystallizes with Methanol, but the enzymatic reaction does not take place and the PQQ ring retains a planar configuration of the oxidized orthoquinone form when ethanol instead of Methanol is present in the crystallization solution.

  • Catalytic mechanism of quinoprotein Methanol Dehydrogenase: A theoretical and x-ray crystallographic investigation
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Ya-jun Zheng, Z.-x. Xia, F. S. Mathews, Zhiwei Chen, Thomas C. Bruice
    Abstract:

    The catalytic mechanism of the reductive half reaction of the quinoprotein Methanol Dehydrogenase (MDH) is believed to proceed either through a hemiketal intermediate or by direct transfer of a hydride ion from the substrate methyl group to the cofactor, pyrroloquinoline quinone (PQQ). A crystal structure of the enzyme-substrate complex of a similar quinoprotein, glucose Dehydrogenase, has recently been reported that strongly favors the hydride transfer mechanism in that enzyme. A theoretical analysis and an improved refinement of the 1.9-A resolution crystal structure of MDH from Methylophilus methylotrophus W3A1 in the presence of Methanol, reported earlier, indicates that the observed tetrahedral configuration of the C-5 atom of PQQ in that study represents the C-5-reduced form of the cofactor and lends support for a hydride transfer mechanism for MDH.

  • Methanol Dehydrogenase structure
    Microbial Growth on C1 Compounds, 1996
    Co-Authors: Z.-x. Xia, W.-w. Dai, S. A. White, G. D. Boyd, F. S. Mathews, V. L. Davidson
    Abstract:

    Methanol Dehydrogenase (MEDH, EC 1.1.99.8) is a soluble quinoprotein located in the periplasmic space of many methylotrophic bacteria (Anthony, 1986). The enzyme catalyzes the oxidation of Methanol to formaldehyde, utilizing the single carbon compound as the sole source of carbon and energy. Other primary alcohols are also substrates of the enzymatic reaction RCH2OH →RCHO +2H+ + 2e- (Duine, Jongejian, 1989). The natural electron acceptor is cytochrome CL, an acidic c-type cytochrome with molecular mass of 17 Kda (Anthony, 1992).

  • ionic strength dependence of the reaction between Methanol Dehydrogenase and cytochrome c 551i evidence of conformationally coupled electron transfer
    Biochemistry, 1994
    Co-Authors: Thomas K. Harris, Z.-x. Xia, Victor L. Davidson, Longyin Chen, F S Mathews
    Abstract:

    The quinoprotein Methanol Dehydrogenase and cytochrome c-551i are two soluble acidic proteins that form a physiological complex in which electrons are transferred from pyrroloquinoline quinone to heme. The oxidation of Methanol Dehydrogenase by the cytochrome was studied as a function of ionic strength using stopped-flow spectroscopy. The dissociation constant (Kd) for complex formation decreased 2-fold with increasing ionic strength from 0.21 to 1.3 M and increased at higher ionic strengths. The rate constant for the electron transfer reaction (kET) increased 2-fold with increasing ionic strength from 0.21 to 1.3 M and decreased at higher ionic strengths. The variation of Kd and kET over this range of ionic strengths was described by Van Leeuwen theory, which takes into account monopole-dipole and dipole-dipole forces, in addition to the monopole-monopole force, to predict the interactions between large molecules. Analysis of the kinetic results in terms of these electrostatic interactions indicated the probable orientations for protein-protein binding and electron transfer. To explain the ionic strength dependence of the observed kET, a model is presented in which the true kET is reduced by a factor Kc, an equilibrium constant that describes some rearrangement of the proteins after a nonoptimal collision to produce the most efficient orientation for electron transfer. This model is consistent with the notion that the large reorganizational energy obtained from temperature-dependence studies of this electron transfer reaction [Harris, T. K., & Davidson, V. L. (1993) Biochemistry 32, 14145-14150] is due to such an intracomplex rearrangement.(ABSTRACT TRUNCATED AT 250 WORDS)

  • The active site structure of the calcium-containing quinoprotein Methanol Dehydrogenase
    Biochemistry, 1993
    Co-Authors: S. A. White, Z.-x. Xia, W.-w. Dai, G. D. Boyd, F. S. Mathews, Yue-fan Zhang, Victor L. Davidson
    Abstract:

    Pyrroloquinoline quinone (PQQ), widely found in nature, serves as the redox cofactor in bacterial Methanol Dehydrogenase (MEDH), a heterotetrameric enzyme that oxidizes Methanol to formaldehyde. The refined structure of MEDH at 2.4-A resolution, based on recently obtained amino acid sequence data, reveals that the PQQ, located in a central channel of the disk-shaped protein, is sandwiched between a Trp side chain and a very unusual vicinal disulfide. A Ca 2+ ion forms a bridge between PQQ and the protein molecule, very close to a putative substrate binding pocket. The vicinal disulfide may form during PQQ incorporation and possibly act to hold the latter in place

R.bruce Lennox - One of the best experts on this subject based on the ideXlab platform.

Shishan. Zhao - One of the best experts on this subject based on the ideXlab platform.