Various Metallopheophorbides as Substrates for Chlorophyll Synthetase

1992 ◽  
Vol 47 (3-4) ◽  
pp. 231-238 ◽  
Author(s):  
Michael Helfrich ◽  
Wolfhart Rüdiger
Keyword(s):  
Metal Ions ◽  
Substrate Binding ◽  
Enzyme Reaction ◽  
Complex Structures ◽  
Pheophorbide A ◽  
Planar Structures ◽  
Square Planar ◽  
Chlorophylls A And B ◽  
Competitive Inhibitors ◽  
Enzyme Test

Abstract Pheophorbide a was prepared from a mixture of chlorophylls a and b by differential extraction with HCl and saponification. The insertion of the following metal ions was investigated: Mg, Zn, Co, Cu, Ni. In the enzyme test with chlorophyll synthetase, the metallopheophorbides fall into two categories: the Mg- and Zn-complexes are good substrates, the Co-, Cu- and Ni-complexes are neither substrates nor competitive inhibitors for the enzyme reaction. This corresponds to two categories of complex structures: Mg- and Zn-porphyrins prefer pentacoordinate square-pyramidal structures, Co-, Cu- and Ni-porphyrins prefer tetracoordinate square-planar structures. A model for substrate binding to chlorophyll synthetase is proposed.

A structural and functional analysis of type III periplasmic and substrate binding proteins: their role in bacterial siderophore and heme transport

2011 ◽  
Vol 392 (1-2) ◽  
Author(s):  
Byron C.H. Chu ◽  
Hans J. Vogel
Keyword(s):  
Binding Proteins ◽  
Substrate Binding ◽  
Transport Systems ◽  
Complex Structures ◽  
Type Iii ◽  
Heme Transport ◽  
Periplasmic Binding Proteins ◽  
Outer Membrane Transporter ◽  
Α Helix ◽  
Carboxy Terminal

AbstractInEscherichia colithe Fhu, Fep and Fec transport systems are involved in the uptake of chelated ferric iron-siderophore complexes, whereas in pathogenic strains heme can also be used as an iron source. An essential step in these pathways is the movement of the ferric-siderophore complex or heme from the outer membrane transporter across the periplasm to the cognate cytoplasmic membrane ATP-dependent transporter. This is accomplished in each case by a dedicated periplasmic binding protein (PBP). Ferric-siderophore binding PBPs belong to the PBP protein superfamily and adopt a bilobal type III structural fold in which the two independently folded amino and carboxy terminal domains are linked together by a single long α-helix of approximately 20 amino acids. Recent structural studies reveal how the PBPs of the Fhu, Fep, Fec and Chu systems are able to bind their corresponding ligands. These complex structures will be discussed and placed in the context of our current understanding of the entire type III family of Gram-negative periplasmic binding proteins and related Gram-positive substrate binding proteins.

scholarly journals Pectin methylesterase, metal ions and plant cell-wall extension. Hydrolysis of pectin by plant cell-wall pectin methylesterase

1991 ◽  
Vol 279 (2) ◽  
pp. 343-350 ◽  
Author(s):  
J Nari ◽  
G Noat ◽  
J Ricard
Keyword(s):  
Cell Wall ◽  
Metal Ions ◽  
Plant Cell ◽  
Plant Cell Wall ◽  
Direct Interaction ◽  
Enzyme Reaction ◽  
Pectin Methylesterase ◽  
High Concentrations ◽  
Enzyme Molecules ◽  
Hydrolysis Of

The hydrolysis of p-nitrophenyl acetate catalysed by pectin methylesterase is competitively inhibited by pectin and does not require metal ions to occur. The results suggest that the activastion by metal ions may be explained by assuming that they interact with the substrate rather than with the enzyme. With pectin used as substrate, metal ions are required in order to allow the hydrolysis to occur in the presence of pectin methylesterase. This is explained by the existence of ‘blocks’ of carboxy groups on pectin that may trap enzyme molecules and thus prevent the enzyme reaction occurring. Metal ions may interact with these negatively charged groups, thus allowing the enzyme to interact with the ester bonds to be cleaved. At high concentrations, however, metal ions inhibit the enzyme reaction. This is again understandable on the basis of the view that some carboxy groups must be adjacent to the ester bond to be cleaved in order to allow the reaction to proceed. Indeed, if these groups are blocked by metal ions, the enzyme reaction cannot occur, and this is the reason for the apparent inhibition of the reaction by high concentrations of metal ions. Methylene Blue, which may be bound to pectin, may replace metal ions in the ‘activation’ and ‘inhibition’ of the enzyme reaction. A kinetic model based on these results has been proposed and fits the kinetic data very well. All the available results favour the view that metal ions do not affect the reaction through a direct interaction with enzyme, but rather with pectin.

scholarly journals Synthesis, Characterization and Antimicrobial Activities of Mixed Ligand Complexes of Fe (II), Co(II), Ni(II) and Cu (II) Ions Derived from Imine of Benzidine and o-phenylenediammine

2020 ◽  
pp. 2762-2775 ◽  
Author(s):  
Hayder Hamied Mihsen ◽  
Suhad Kareem Abass ◽  
Maysaa Taqe Abed –Alhasan ◽  
Zainab M. Hassan ◽  
Ali Kreem Abass
Keyword(s):  
Metal Ions ◽  
Antimicrobial Activities ◽  
Fungal Species ◽  
Molar Ratio ◽  
Appreciable Change ◽  
Gram Positive Bacteria ◽  
Square Planar ◽  
Bacillus Spp ◽  
Ft Ir ◽  
Apparent Stability

Binuclear metal complexes of the metal ions Fe (II), Co (II), Ni (II) and Cu (II) were synthesized by the reaction of these metal ions with the imine of benzidine (H2L) as a primary ligand and o-phenylenediammine (OPD) as a secondary ligand  in a molar ratio of 2:2:1. The prepared complexes were characterized using CHN elemental analysis, FT-IR, UV-visible, molar conductivity, magnetic susceptibility and TGA-DTA thermogravimetric analysis. All the prepared complexes showed apparent stability and could be stored for months without any appreciable change. According to the results obtained by elemental and spectral analyses, a tetrahedral structure is suggested for all the prepared complexes, except for the copper complex which showed a square planar structure. The antimicrobial activities of these complexes were evaluated against Bacillus spp. (Gram-negative bacteria), Proteus spp. (Gram-positive bacteria) and Aspergillus niger (A. niger, a fungal species). The results showed that all the prepared complexes have no apparent effects on Bacillus spp. viability, whereas Proteus spp.  and A. niger were affected significantly.

Binuclear metal chelate complexes of anthraquinones having a MO4 chromophore. Part 1. Quinizarin

1987 ◽  
Vol 65 (7) ◽  
pp. 1485-1490 ◽  
Author(s):  
M. N. Bakola-Christianopoulou ◽  
P. D. Akrivos ◽  
M. Baumgarten
Keyword(s):  
Metal Ions ◽  
Magnetic Measurements ◽  
Metal Chelate ◽  
Transition Elements ◽  
Chelate Complexes ◽  
Cobalt Nickel ◽  
Oxygen Donor ◽  
Nickel Copper ◽  
Square Planar ◽  
Coordination Spheres

Homobinuclear metal chelate complexes having 1,4-dihydroxy-9,10-anthracenedione (quinizarin) as a bridging unit have been prepared with four bivalent first row transition elements, namely cobalt, nickel, copper, and zinc. The coordination spheres of the metal ions consist of two nearly equivalent six-membered rings with oxygen donor atoms derived from the quinizarin and the terminal ligands which are either β-diketones or salicylic aldehyde. TG, spectroscopic (ir, uv–vis, epr), and magnetic measurements have been applied to an investigation of the geometry adopted by the MO4 chromophores. The results are consistent with varying degrees of distortion from the ideal square planar toward a tetrahedral arrangement around the metal ions, closely related to the specific metal center involved.

scholarly journals Discovery and Design of Novel Small Molecule GSK-3 Inhibitors Targeting the Substrate Binding Site

2020 ◽  
Vol 21 (22) ◽  
pp. 8709
Author(s):  
Ido Rippin ◽  
Netaly Khazanov ◽  
Shirley Ben Joseph ◽  
Tania Kudinov ◽  
Eva Berent ◽  
...  
Keyword(s):  
Binding Site ◽  
Small Molecule ◽  
Substrate Binding ◽  
Pharmacophore Model ◽  
Drug Induced ◽  
Substrate Binding Site ◽  
Zinc Database ◽  
Competitive Inhibitors ◽  
Ic50 Values ◽  
Critical Binding

The serine/threonine kinase, GSK-3, is a promising drug discovery target for treating multiple pathological disorders. Most GSK-3 inhibitors that were developed function as ATP competitive inhibitors, with typical limitations in specificity, safety and drug-induced resistance. In contrast, substrate competitive inhibitors (SCIs), are considered highly selective, and more suitable for clinical practice. The development of SCIs has been largely neglected in the past because the ambiguous, undefined nature of the substrate-binding site makes them difficult to design. In this study, we used our previously described structural models of GSK-3 bound to SCI peptides, to design a pharmacophore model and to virtually screen the “drug-like” Zinc database (~6.3 million compounds). We identified leading hits that interact with critical binding elements in the GSK-3 substrate binding site and are chemically distinct from known GSK-3 inhibitors. Accordingly, novel GSK-3 SCI compounds were designed and synthesized with IC50 values of~1–4 μM. Biological activity of the SCI compound was confirmed in cells and in primary neurons that showed increased β-catenin levels and reduced tau phosphorylation in response to compound treatment. We have generated a new type of small molecule GSK-3 inhibitors and propose to use this strategy to further develop SCIs for other protein kinases.

Inhibition of glycogen synthase (casein) kinase-1 by divalent metal ions

1988 ◽  
Vol 66 (3) ◽  
pp. 238-243 ◽  
Author(s):  
Toolsee J. Singh
Keyword(s):  
Metal Ions ◽  
Kinase Activity ◽  
Glycogen Synthase ◽  
Divalent Metal ◽  
Casein Kinase ◽  
The Other ◽  
Divalent Metal Ions ◽  
Casein Kinase 1 ◽  
Competitive Inhibitors ◽  
Noncompetitive Inhibitors

The specificity of glycogen synthase (casein) kinase-1 (CK-1) for different divalent metal ions was explored in this study. Of nine metal ions (Mg2+, Mn2+, Zn2+, Cu2+, Ca2+, Ba2+, Ni2+, Co2+, Fe2+) tested, only Mg2+ supported significant kinase activity. Several of the other metals, however, inhibited the Mg2+-stimulated kinase activity. Half-maximal inhibitions by Mn2+, Zn2+, Co2+, Fe2+, and Ni2+ were observed at 55, 65, 110, 125, and 284 μM, respectively. Kinetic analyses indicate that the metal ions are acting as competitive inhibitors of CK-1 with respect to the protein substrate (casein) and as noncompetitive inhibitors with respect to the nucleotide substrate (ATP). The inhibition of CK-1 by the different metal ions can be reversed by EGTA.

Characterization of substrate binding and enzymatic removal of a 3-methyladenine lesion from genomic DNA with TAG of MDR A. baumannii

2016 ◽  
Vol 12 (11) ◽  
pp. 3259-3265 ◽  
Author(s):  
Jyoti Singh Tomar ◽  
Manju Narwal ◽  
Pravindra Kumar ◽  
Rama Krishna Peddinti
Keyword(s):  
Genomic Dna ◽  
Substrate Binding ◽  
Binding Parameters ◽  
Competitive Inhibitors ◽  
Adenine Base

The binding parameters of substrates with enzyme TAG revealed that it exhibits selectivity for 3mA over the normal adenine base. The results obtained from the experiments are useful in designing of competitive inhibitors.

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