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Bernt Krebs - One of the best experts on this subject based on the ideXlab platform.

  • Purification and spectroscopic studies on Catechol Oxidase from lemon balm (Melissa officinalis).
    Phytochemistry, 2012
    Co-Authors: Annette Rompel, Klaudia Büldt-karentzopoulos, Christian Molitor, Bernt Krebs
    Abstract:

    A Catechol Oxidase from lemon balm (Melissa officinalis) moCO which only catalyzes the oxidation of Catechols to quinones without hydroxylating tyrosine was purified. The molecular mass of the M. officinalis enzyme of 39,370 Da was obtained by MALDI mass spectrometry and the isoelectric point was determined to be 3.4. Addition of 2 eq. H(2)O(2) to the enzyme leads to oxy Catechol Oxidase. In the UV/Vis spectrum two new absorption bands occur at 343 nm (e=8510 M(-1)cm(-1)) and 580 nm (e=580 M(-1)cm(-1)) due to O(2)(2-)Cu (II) charge transfer transitions in accordance with the oxy forms of other type 3 copper proteins. The N-terminal sequence has been determined by Edman degradation to NPVQAPELDKCGTAT, exhibiting a proline at the second and sixth position conserved in other polyphenol Oxidases.

  • Comparative modeling of the latent form of a plant Catechol Oxidase using a molluskan hemocyanin structure.
    Journal of inorganic biochemistry, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Hans Joachim Galla, Bernt Krebs
    Abstract:

    The structure of the precursor form of Catechol Oxidase from sweet potatoes (Ipomoea batatas) has been modeled on the basis of the 3D structural data of mature Catechol Oxidase [Nat. Struct. Biol. 5 (1998) 1084] and of hemocyanin from giant octopus (Octopus dofleini) [J. Mol. Biol. 278 (1998) 855]. A C-terminal extension peptide is found in the cDNA sequence but not in the purified, mature form of Catechol Oxidase. Superimposition of the 3D structures of the native hemocyanin and Catechol Oxidase reveals a close relationship except for an additional C-terminal domain only found in the hemocyanin structure. As sequence alignment shows good homology this domain of the hemocyanin structure was used as a template to model the 3D structure of the C-terminal extension peptide of Catechol Oxidase. As hemocyanins show no or only weak Catecholase activity due to this domain this indicates an inhibitory function of this extension peptide. Beside this possible shielding function for the precursor form, evidence for a function in copper-uptake also increases due to the location of three histidine residues in the model.

  • the crystal structure of Catechol Oxidase new insight into the function of type 3 copper proteins
    Accounts of Chemical Research, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Bernt Krebs
    Abstract:

    The crystal structure of Catechol Oxidase reveals new insight into the functional properties of the type-3 copper proteins. This class of proteins includes the closely related and better-known tyrosinase as well as hemocyanin, an oxygen transport protein. All these proteins have a dinuclear copper center, have similar spectroscopic behaviors, and show close evolutionary and functional relationships. Comparison between the 3D structures of Catechol Oxidase and hemocyanins reveals the structural reasons for the divergence in function.

  • Isozymes of Ipomoea batatas Catechol Oxidase differ in catalase-like activity.
    Biochimica et biophysica acta, 2001
    Co-Authors: Carsten Gerdemann, Annette Magrini, Christoph Eicken, Annette Rompel, Helmut E. Meyer, Friedrich Spener, Bernt Krebs
    Abstract:

    Abstract The amino acid sequences of two isozymes of Catechol Oxidase from sweet potatoes ( Ipomoea batatas ) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant Catechol Oxidases revealed about 80% equidistance between the two I. batatas Catechol Oxidases and approximately 40–60% to Catechol Oxidases of other plants. When H 2 O 2 was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.

  • Catechol Oxidase - structure and activity.
    Current Opinion in Structural Biology, 1999
    Co-Authors: Christoph Eicken, Bernt Krebs, James C. Sacchettini
    Abstract:

    Recently determined structures of copper-containing plant Catechol Oxidase in three different catalytic states have provided new insights into the mechanism of this enzyme and its relationship to other copper type-3 proteins. Moreover, the active site of Catechol Oxidase has been found to be structurally conserved with the oxygen-binding site of a molluscan hemocyanin.

Shouvik Chattopadhyay - One of the best experts on this subject based on the ideXlab platform.

Christoph Eicken - One of the best experts on this subject based on the ideXlab platform.

  • Comparative modeling of the latent form of a plant Catechol Oxidase using a molluskan hemocyanin structure.
    Journal of inorganic biochemistry, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Hans Joachim Galla, Bernt Krebs
    Abstract:

    The structure of the precursor form of Catechol Oxidase from sweet potatoes (Ipomoea batatas) has been modeled on the basis of the 3D structural data of mature Catechol Oxidase [Nat. Struct. Biol. 5 (1998) 1084] and of hemocyanin from giant octopus (Octopus dofleini) [J. Mol. Biol. 278 (1998) 855]. A C-terminal extension peptide is found in the cDNA sequence but not in the purified, mature form of Catechol Oxidase. Superimposition of the 3D structures of the native hemocyanin and Catechol Oxidase reveals a close relationship except for an additional C-terminal domain only found in the hemocyanin structure. As sequence alignment shows good homology this domain of the hemocyanin structure was used as a template to model the 3D structure of the C-terminal extension peptide of Catechol Oxidase. As hemocyanins show no or only weak Catecholase activity due to this domain this indicates an inhibitory function of this extension peptide. Beside this possible shielding function for the precursor form, evidence for a function in copper-uptake also increases due to the location of three histidine residues in the model.

  • the crystal structure of Catechol Oxidase new insight into the function of type 3 copper proteins
    Accounts of Chemical Research, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Bernt Krebs
    Abstract:

    The crystal structure of Catechol Oxidase reveals new insight into the functional properties of the type-3 copper proteins. This class of proteins includes the closely related and better-known tyrosinase as well as hemocyanin, an oxygen transport protein. All these proteins have a dinuclear copper center, have similar spectroscopic behaviors, and show close evolutionary and functional relationships. Comparison between the 3D structures of Catechol Oxidase and hemocyanins reveals the structural reasons for the divergence in function.

  • Isozymes of Ipomoea batatas Catechol Oxidase differ in catalase-like activity.
    Biochimica et biophysica acta, 2001
    Co-Authors: Carsten Gerdemann, Annette Magrini, Christoph Eicken, Annette Rompel, Helmut E. Meyer, Friedrich Spener, Bernt Krebs
    Abstract:

    Abstract The amino acid sequences of two isozymes of Catechol Oxidase from sweet potatoes ( Ipomoea batatas ) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant Catechol Oxidases revealed about 80% equidistance between the two I. batatas Catechol Oxidases and approximately 40–60% to Catechol Oxidases of other plants. When H 2 O 2 was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.

  • Catechol Oxidase - structure and activity.
    Current Opinion in Structural Biology, 1999
    Co-Authors: Christoph Eicken, Bernt Krebs, James C. Sacchettini
    Abstract:

    Recently determined structures of copper-containing plant Catechol Oxidase in three different catalytic states have provided new insights into the mechanism of this enzyme and its relationship to other copper type-3 proteins. Moreover, the active site of Catechol Oxidase has been found to be structurally conserved with the oxygen-binding site of a molluscan hemocyanin.

  • substrate specificity of Catechol Oxidase from lycopus europaeus and characterization of the bioproducts of enzymic caffeic acid oxidation1
    FEBS Letters, 1999
    Co-Authors: Annette Rompel, Dirk Meiwes, Klaudia Buldtkarentzopoulos, Annette Magrini, Carsten Gerdemann, Christoph Eicken, Helmut Fischer, Bernt Krebs
    Abstract:

    The substrate specificity of Catechol Oxidase from Lycopus europaeus towards phenols is examined. The enzyme catalyzes the oxidation of o-diphenols to o-quinones without hydroxylating monophenols, the additional activity of tyrosinase. Substrates containing a -COOH group are inhibitors for Catechol Oxidase. The products of enzymic oxidation of caffeic acid were analyzed and isolated by HPLC with diode array detection. The neolignans of the 2,3-dihydro-1,4-benzodioxin type (3, 6–8), 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-2,3-dicarboxy-1,2-dihydronaphthaline (1) 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-3-carboxynaphthaline (5) and 2,6-bis-(3′,4′-dihydroxyphenyl)-1-carboxy-3-oxacyclo-(3,0)-pentan-2-on-1-ene (4) were formed. A reaction mechanism for the formation of (1, 4 and 5) is discussed.

Nina Hakulinen - One of the best experts on this subject based on the ideXlab platform.

  • Unraveling Substrate Specificity and Catalytic Promiscuity of Aspergillus oryzae Catechol Oxidase.
    Chembiochem : a European journal of chemical biology, 2018
    Co-Authors: Leena Penttinen, Chiara Rutanen, Juha Rouvinen, Janne Jänis, Nina Hakulinen
    Abstract:

    Catechol Oxidases and tyrosinases are coupled binuclear copper enzymes that oxidize various o-diphenolic compounds to corresponding o-quinones. Tyrosinases have an additional monooxygenation ability to hydroxylate monophenol to o-diphenol. It is still not clear what causes the difference in the catalytic activities. We solved a complex structure of Aspergillus oryzae Catechol Oxidase with resorcinol bound into the active site. Catalytic activity of A. oryzae Catechol Oxidase was studied, for the first time, by high-resolution FT-ICR mass spectrometry to shed light on the reaction mechanism. The enzyme was also found to catalyze monooxygenation of small phenolics, which provides a novel perspective for the discussion of differences in the catalytic activity between tyrosinases and Catechol Oxidases. According to the results, two binding modes for resorcinol are suggested and a reaction mechanism for coupled binuclear copper enzymes is discussed.

  • A new crystal form of Aspergillus oryzae Catechol Oxidase and evaluation of copper site structures in coupled binuclear copper enzymes.
    PloS one, 2018
    Co-Authors: Leena Penttinen, Chiara Rutanen, Markku Saloheimo, Kristiina Kruus, Juha Rouvinen, Nina Hakulinen
    Abstract:

    Coupled binuclear copper (CBC) enzymes have a conserved type 3 copper site that binds molecular oxygen to oxidize various mono- and diphenolic compounds. In this study, we found a new crystal form of Catechol Oxidase from Aspergillus oryzae (AoCO4) and solved two new structures from two different crystals at 1.8-A and at 2.5-A resolutions. These structures showed different copper site forms (met/deoxy and deoxy) and also differed from the copper site observed in the previously solved structure of AoCO4. We also analysed the electron density maps of all of the 56 CBC enzyme structures available in the protein data bank (PDB) and found that many of the published structures have vague copper sites. Some of the copper sites were then re-refined to find a better fit to the observed electron density. General problems in the refinement of metalloproteins and metal centres are discussed.

  • Tyrosinase and Catechol Oxidase activity.
    2018
    Co-Authors: Leena Penttinen, Chiara Rutanen, Markku Saloheimo, Kristiina Kruus, Juha Rouvinen, Nina Hakulinen
    Abstract:

    Tyrosinase and Catechol Oxidase activity.

  • The crystal structure of an extracellular Catechol Oxidase from the ascomycete fungus Aspergillus oryzae
    JBIC Journal of Biological Inorganic Chemistry, 2013
    Co-Authors: Nina Hakulinen, Kristiina Kruus, Heidi Kaljunen, Chiara Gasparetti, Juha Rouvinen
    Abstract:

    Catechol Oxidases (EC 1.10.3.1) catalyse the oxidation of o -diphenols to their corresponding o -quinones. These Oxidases contain two copper ions (CuA and CuB) within the so-called coupled type 3 copper site as found in tyrosinases (EC 1.14.18.1) and haemocyanins. The crystal structures of a limited number of bacterial and fungal tyrosinases and plant Catechol Oxidases have been solved. In this study, we present the first crystal structure of a fungal Catechol Oxidase from Aspergillus oryzae (AoCO4) at 2.5-Å resolution. AoCO4 belongs to the newly discovered family of short-tyrosinases, which are distinct from other tyrosinases and Catechol Oxidases because of their lack of the conserved C-terminal domain and differences in the histidine pattern for CuA. The sequence identity of AoCO4 with other structurally known enzymes is low (less than 30 %), and the crystal structure of AoCO4 diverges from that of enzymes belonging to the conventional tyrosinase family in several ways, particularly around the central α-helical core region. A diatomic oxygen moiety was identified as a bridging molecule between the two copper ions CuA and CuB separated by a distance of 4.2–4.3 Å. The UV/vis absorption spectrum of AoCO4 exhibits a distinct maximum of absorbance at 350 nm, which has been reported to be typical of the oxy form of type 3 copper enzymes.

  • Crystallization and preliminary X-ray analysis of Aspergillus oryzae Catechol Oxidase.
    Acta crystallographica. Section F Structural biology and crystallization communications, 2011
    Co-Authors: Heidi Kaljunen, Kristiina Kruus, Juha Rouvinen, Chiara Gasparetti, Nina Hakulinen
    Abstract:

    Catechol Oxidase is an enzyme that catalyzes the oxidation of o-diphenols to the corresponding o-quinones. It is a copper-containing enzyme with a binuclear copper active site. Here, the crystallization and multiple-wavelength anomalous dispersion data collection of Catechol Oxidase from the mould fungus Aspergillus oryzae are described. During the purification, three forms of the enzyme (39.3, 40.5 and 44.3 kDa) were obtained. A mixture of these three forms was initially crystallized and gave crystals that diffracted to 2.5 Å resolution and belonged to space group P3(2)21, with unit-cell parameters a = b = 118.9, c = 84.5 Å, α = β = 90, γ = 120°. A preparation containing only the shorter form (39.3 kDa) produced crystals that diffracted to 2.9 Å resolution and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 51.8, b = 95.3, c = 139.5 Å, α = β = γ = 90°.

Carsten Gerdemann - One of the best experts on this subject based on the ideXlab platform.

  • Comparative modeling of the latent form of a plant Catechol Oxidase using a molluskan hemocyanin structure.
    Journal of inorganic biochemistry, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Hans Joachim Galla, Bernt Krebs
    Abstract:

    The structure of the precursor form of Catechol Oxidase from sweet potatoes (Ipomoea batatas) has been modeled on the basis of the 3D structural data of mature Catechol Oxidase [Nat. Struct. Biol. 5 (1998) 1084] and of hemocyanin from giant octopus (Octopus dofleini) [J. Mol. Biol. 278 (1998) 855]. A C-terminal extension peptide is found in the cDNA sequence but not in the purified, mature form of Catechol Oxidase. Superimposition of the 3D structures of the native hemocyanin and Catechol Oxidase reveals a close relationship except for an additional C-terminal domain only found in the hemocyanin structure. As sequence alignment shows good homology this domain of the hemocyanin structure was used as a template to model the 3D structure of the C-terminal extension peptide of Catechol Oxidase. As hemocyanins show no or only weak Catecholase activity due to this domain this indicates an inhibitory function of this extension peptide. Beside this possible shielding function for the precursor form, evidence for a function in copper-uptake also increases due to the location of three histidine residues in the model.

  • the crystal structure of Catechol Oxidase new insight into the function of type 3 copper proteins
    Accounts of Chemical Research, 2002
    Co-Authors: Carsten Gerdemann, Christoph Eicken, Bernt Krebs
    Abstract:

    The crystal structure of Catechol Oxidase reveals new insight into the functional properties of the type-3 copper proteins. This class of proteins includes the closely related and better-known tyrosinase as well as hemocyanin, an oxygen transport protein. All these proteins have a dinuclear copper center, have similar spectroscopic behaviors, and show close evolutionary and functional relationships. Comparison between the 3D structures of Catechol Oxidase and hemocyanins reveals the structural reasons for the divergence in function.

  • Isozymes of Ipomoea batatas Catechol Oxidase differ in catalase-like activity.
    Biochimica et biophysica acta, 2001
    Co-Authors: Carsten Gerdemann, Annette Magrini, Christoph Eicken, Annette Rompel, Helmut E. Meyer, Friedrich Spener, Bernt Krebs
    Abstract:

    Abstract The amino acid sequences of two isozymes of Catechol Oxidase from sweet potatoes ( Ipomoea batatas ) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant Catechol Oxidases revealed about 80% equidistance between the two I. batatas Catechol Oxidases and approximately 40–60% to Catechol Oxidases of other plants. When H 2 O 2 was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.

  • substrate specificity of Catechol Oxidase from lycopus europaeus and characterization of the bioproducts of enzymic caffeic acid oxidation1
    FEBS Letters, 1999
    Co-Authors: Annette Rompel, Dirk Meiwes, Klaudia Buldtkarentzopoulos, Annette Magrini, Carsten Gerdemann, Christoph Eicken, Helmut Fischer, Bernt Krebs
    Abstract:

    The substrate specificity of Catechol Oxidase from Lycopus europaeus towards phenols is examined. The enzyme catalyzes the oxidation of o-diphenols to o-quinones without hydroxylating monophenols, the additional activity of tyrosinase. Substrates containing a -COOH group are inhibitors for Catechol Oxidase. The products of enzymic oxidation of caffeic acid were analyzed and isolated by HPLC with diode array detection. The neolignans of the 2,3-dihydro-1,4-benzodioxin type (3, 6–8), 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-2,3-dicarboxy-1,2-dihydronaphthaline (1) 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-3-carboxynaphthaline (5) and 2,6-bis-(3′,4′-dihydroxyphenyl)-1-carboxy-3-oxacyclo-(3,0)-pentan-2-on-1-ene (4) were formed. A reaction mechanism for the formation of (1, 4 and 5) is discussed.