Structural diversity in metal ion chelation, and the structure of uro'gen III synthase

2002 ◽  
Vol 30 (3) ◽  
pp. A48-A48
Author(s):  
H. L. Schubert ◽  
E. Raux ◽  
M. A. A. Mathews ◽  
J. D. Phillips ◽  
K. S. Wilson ◽  
...  
Keyword(s):  
Metal Ion ◽  
Structural Diversity ◽  
Metal Ion Chelation

Structural diversity in metal ion chelation and the structure of uroporphyrinogen III synthase

2002 ◽  
Vol 30 (4) ◽  
pp. 595-600 ◽  
Author(s):  
H. L. Schubert ◽  
E. Raux ◽  
M. A. A. Matthews ◽  
J. D. Phillips ◽  
K. S. Wilson ◽  
...  
Keyword(s):  
Active Site ◽  
Metal Ion ◽  
Structural Diversity ◽  
Structural Similarity ◽  
Ring Closure ◽  
Catalytic Reactions ◽  
Central Metal ◽  
Tertiary Structures ◽  
Bacillus Subtilus ◽  
Metal Ion Chelation

All tetrapyrroles are synthesized through a branched pathway, and although each tetrapyrrole receives unique modifications around the ring periphery, they all share the unifying feature of a central metal ion. Each pathway maintains a unique metal ion chelatase, and several tertiary structures have been determined, including those of the protoporphyrin ferrochelatase from both human and Bacillus subtilus, and the cobalt chelatase CbiK. These enzymes exhibit strong structural similarity and appear to function by a similar mechanism. Met8p, from Saccharomyces cerevisiae, catalyses ferrochelation during the synthesis of sirohaem, and the structure reveals a novel chelatase architecture whereby both ferrochelation and NAD+-dependent dehydrogenation take place in a single bifunctional active site. Asp-141 appears to participate in both catalytic reactions. The final common biosynthetic step in tetrapyrrole biosynthesis is the generation of uroporphyrinogen by uroporphyrinogen III synthase, whereby the D ring of hydroxymethylbilane is flipped during ring closure to generate the asymmetrical structure of uroporphyrinogen III. The recently derived structure of uroporphyrinogen III synthase reveals a bi-lobed structure in which the active site lies between the domains.

Marine Metabolites and Metal Ion Chelation

2012 ◽  
pp. 861-892 ◽  
Author(s):  
Stephen H. Wright ◽  
Andrea Raab ◽  
Jörg Feldmann ◽  
Eva Krupp ◽  
Marcel Jaspars
Keyword(s):  
Metal Ion ◽  
Marine Metabolites ◽  
Metal Ion Chelation

scholarly journals Synergy Effects in Heavy Metal Ion Chelation with Aryl- and Aroyl-Substituted Thiourea Derivatives

2021 ◽  
Author(s):  
Ransel Barzaga ◽  
Lucia Lestón-Sánchez ◽  
Fernando Aguilar-Galindo ◽  
Osvaldo Estévez-Hernández ◽  
Sergio Díaz-Tendero
Keyword(s):  
Heavy Metal ◽  
Metal Ion ◽  
Heavy Metal Ion ◽  
Thiourea Derivatives ◽  
Synergy Effects ◽  
Metal Ion Chelation

Electronic Effects on the Bergman Cyclisation of Enediynes. A Review

2004 ◽  
Vol 69 (5) ◽  
pp. 945-965 ◽  
Author(s):  
Michael Klein ◽  
Thomas Walenzyk ◽  
Burkhard König
Keyword(s):  
Experimental Data ◽  
Metal Ion ◽  
Substituent Effects ◽  
Terminal Alkyne ◽  
Electronic Effects ◽  
Ring Strain ◽  
Clear Cut ◽  
Theoretical Predictions ◽  
Metal Ion Chelation

The thermal cyclisation of enediynes to benzene-1,4-diyl diradicals (Bergman cyclisation) is affected by geometrical and electronic conditions. While the effect of ring strain or conformational constrains on the cyclisation temperature has been investigated in detail, electronic contributions have been less studied. Often geometrical and electronic contributions cannot be clearly distinguished. In most cases metal ion chelation does involve both. In this review we have summarised clear-cut observations of electronic substituents effects on the thermal enediyne reactivity. The effects of substituents in the vinylic and terminal alkyne position, the influence of benzo-fusion and hetarene fusion, as well as the changes induced by heteroatoms in the enediyne skeleton, are within the scope of this review. With the exception of more complex heterocyclic hetarene-fused enediynes the experimental data of electronic substituent effects on the thermal Bergman cyclisation of enediynes follow theoretical predictions. A review with 57 references.

scholarly journals In vitro antioxidant, 𝛼-amylase and 𝛼-glucosidase activities of methanol extracts from three Momordica species

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Olubunmi Adenike Akinwunmi
Keyword(s):  
Metal Ion ◽  
Antioxidant Activities ◽  
Biological Activities ◽  
Total Phenolic ◽  
Limited Information ◽  
Glucosidase Inhibitors ◽  
Dpph Scavenging ◽  
Oral Hypoglycemic Drugs ◽  
Metal Ion Chelation

<p>Antioxidant based drug preparations are used in the prevention and management of complex diseases which include atherosclerosis, stroke, diabetes, alzheimer’s disease and cancer. Diabetes mellitus is a metabolic disorder of glucose metabolism. The management of blood glucose level is the hallmark in the treatment of this ailment, which may be achieved through the use of oral hypoglycemic drugs such as biguanides, insulin secretagogues, and 𝛼-amylase and glucosidase inhibitors. Although several biological activities had been reported for  <em>Momordica</em> <em>foetida </em>and <em>Momordica</em> <em>charantia</em>; it appears there is limited information on the  biological activity of <em>Momordica</em> <em>cissoides</em>. The purpose of this study is to compare the antioxidant, 𝛼-amylase and 𝛼-glucosidase inhibitory activities of <em>Momordica</em> <em>charantia </em>(M1), <em>Momordica</em> <em>foetida </em>(M2)<em>, </em>and <em>Momordica</em> <em>cissoides</em>  (M3) to establish a chemotaxonomic relationship between them. The antioxidant activities measured by DPPH scavenging properties, metal ion chelation, hydrogen peroxide scavenging and ABTS revealed that <em>M. foetida</em> had the highest inhibition potential, followed by <em>M. charantia</em> and the least being <em>M. cissoides</em>. In contrast, the antioxidant activities measured by FRAP,  the total phenolic content , flavonoids and tannins revealed that <em>M. cissoides</em> had the best antioxidant potential, while <em>M. foetida</em> had the least activity. The comparative α-amylase and glucosidase inhibitory studies performed demonstrated that the extracts of <em>M.cissoides </em>had the highest inhibitory potentials. Thus, the plant can be used in the management of diabetes.</p>

Antibacterial Mechanism of Long-Chain Polyphosphates in Staphylococcus aureus

1994 ◽  
Vol 57 (4) ◽  
pp. 289-294 ◽  
Author(s):  
RUBY M. LEE ◽  
PAUL A. HARTMAN ◽  
H. MICHAEL STAHR ◽  
DENNIS G. OLSON ◽  
FRED D. WILLIAMS
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Cell Walls ◽  
Metal Ion ◽  
Antibacterial Mechanism ◽  
Essential Metals ◽  
Bacterial Leakage ◽  
Metal Ion Chelation ◽  
Free Metal ◽  
Long Chain

The results of previous studies indicated that the antibacterial effects of long-chain polyphosphates (sodium polyphosphate glassy [SPG] and sodium ultraphosphate [UP]) to Staphylococcus aureus ISP40 8325 could be attributed to damage to the cell envelope (cell wall or cell membrane). Also, Ca2+ (0.01 M) or Mg2+ (0.01 M) reversed the bactericidal and bacteriolytic effects of polyphosphates in S. aureus. In the present study, 0.4 M sodium chloride (NaCl) protected the cells from leakage caused by SPG and 0.6 M NaCl protected the cells from leakage by UP. Polymyxin, a peptide antibiotic that causes cell membrane damage, induced leakage even in the presence of 0.6 M NaCl. In the presence of 0.4 M NaCl, bacterial leakage was significantly reduced by disodium ethylenediamine tetraacetate (EDTA), a metal chelator that causes cell wall damage. Bacterial leakage by polyphosphates was significantly greater at pH 8 than at pH 6, which suggested that metal-ion chelation was involved in the antibacterial mechanism. A dialysis membrane (MWCO 100) was used to separate free metal and polyphosphate-bound metal. Levels of free Ca2+ and Mg2+ in polyphosphate-treated cells were significantly lower than those of the cells without polyphosphate. This free-metal dialysis study provided Chemical evidence to show that long-chain polyphosphates interacted with S. aureus cell walls by a metal-ion chelation mechanism. In addition, long-chain polyphosphates were shown to bind to the cell wall, chelate metals, and remain bound without releasing metal ions from the cell wall into the suspending medium. A hypothesis is proposed in which the antibacterial mechanism of long-chain polyphosphates is caused by binding of long-chain polyphosphates to the cell wall of early-exponential phase cells of S. aureus ISP40 8325. The polyphosphates chelate structurally essential metals (Ca2+ and Mg2+) of the cell wall, resulting in bactericidal and bacteriolytic effects. The structurally essential metals probably form cross bridges between the teichoic acid chains in the cell walls of gram-positive bacteria.

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