scholarly journals The Biochemical Properties of Manganese in Plants

Plants ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 381 ◽  
Author(s):  
Schmidt ◽  
Husted
Keyword(s):  
Metal Ions ◽  
Oxidation State ◽  
Metal Binding ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Biochemical Properties ◽  
Oxygen Evolving Complex ◽  
Functional Roles ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions

Manganese (Mn) is an essential micronutrient with many functional roles in plant metabolism. Manganese acts as an activator and co-factor of hundreds of metalloenzymes in plants. Because of its ability to readily change oxidation state in biological systems, Mn plays and important role in a broad range of enzyme-catalyzed reactions, including redox reactions, phosphorylation, decarboxylation, and hydrolysis. Manganese(II) is the prevalent oxidation state of Mn in plants and exhibits fast ligand exchange kinetics, which means that Mn can often be substituted by other metal ions, such as Mg(II), which has similar ion characteristics and requirements to the ligand environment of the metal binding sites. Knowledge of the molecular mechanisms catalyzed by Mn and regulation of Mn insertion into the active site of Mn-dependent enzymes, in the presence of other metals, is gradually evolving. This review presents an overview of the chemistry and biochemistry of Mn in plants, including an updated list of known Mn-dependent enzymes, together with enzymes where Mn has been shown to exchange with other metal ions. Furthermore, the current knowledge of the structure and functional role of the three most well characterized Mn-containing metalloenzymes in plants; the oxygen evolving complex of photosystem II, Mn superoxide dismutase, and oxalate oxidase is summarized.

scholarly journals Metal ions and redox balance regulate distinct amyloid-like aggregation pathways of GAPR-1

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jie Sheng ◽  
Nick K. Olrichs ◽  
Willie J. Geerts ◽  
Dora V. Kaloyanova ◽  
J. Bernd Helms
Keyword(s):  
Metal Ions ◽  
Metal Binding ◽  
Molecular Mechanisms ◽  
Quaternary Structure ◽  
Copper Ions ◽  
Redox Homeostasis ◽  
Secretory Proteins ◽  
Pathogenesis Related Protein ◽  
Pathogenesis Related ◽  
Induced Aggregation

Abstract Members of the CAP superfamily (Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-Related 1 proteins) are characterized by the presence of a structurally conserved CAP domain. The common structure-function relationship of this domain is still poorly understood. In this study, we unravel specific molecular mechanisms modulating the quaternary structure of the mammalian CAP protein GAPR-1 (Golgi-Associated plant Pathogenesis-Related protein 1). Copper ions are shown to induce a distinct amyloid-like aggregation pathway of GAPR-1 in the presence of heparin. This involves an immediate shift from native multimers to monomers which are prone to form amyloid-like fibrils. The Cu2+-induced aggregation pathway is independent of a conserved metal-binding site and involves the formation of disulfide bonds during the nucleation process. The elongation process occurs independently of the presence of Cu2+ ions, and amyloid-like aggregation can proceed under oxidative conditions. In contrast, the Zn2+-dependent aggregation pathway was found to be independent of cysteines and was reversible upon removal of Zn2+ ions. Together, our results provide insight into the regulation of the quaternary structure of GAPR-1 by metal ions and redox homeostasis with potential implications for regulatory mechanisms of other CAP proteins.

Temperature, Dynamics, and Enzyme-Catalyzed Reaction Rates

2020 ◽  
Vol 49 (1) ◽  
pp. 163-180 ◽  
Author(s):  
Vickery L. Arcus ◽  
Adrian J. Mulholland
Keyword(s):  
Molecular Mechanisms ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Rate Theory ◽  
Different Temperatures ◽  
State Ensemble ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Transition State Ensemble ◽  
Rate Limiting

We review the adaptations of enzyme activity to different temperatures. Psychrophilic (cold-adapted) enzymes show significantly different activation parameters (lower activation enthalpies and entropies) from their mesophilic counterparts. Furthermore, there is increasing evidence that the temperature dependence of many enzyme-catalyzed reactions is more complex than is widely believed. Many enzymes show curvature in plots of activity versus temperature that is not accounted for by denaturation or unfolding. This is explained by macromolecular rate theory: A negative activation heat capacity for the rate-limiting chemical step leads directly to predictions of temperature optima; both entropy and enthalpy are temperature dependent. Fluctuations in the transition state ensemble are reduced compared to the ground state. We show how investigations combining experiment with molecular simulation are revealing fundamental details of enzyme thermoadaptation that are relevant for understanding aspects of enzyme evolution. Simulations can calculate relevant thermodynamic properties (such as activation enthalpies, entropies, and heat capacities) and reveal the molecular mechanisms underlying experimentally observed behavior.

scholarly journals Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators

2013 ◽  
Vol 24 (4) ◽  
pp. 433-439 ◽  
Author(s):  
Jonathan M. Scholey
Keyword(s):  
Intracellular Transport ◽  
Molecular Mechanisms ◽  
Equilibrium Constants ◽  
Reaction Coordinate ◽  
Simple Chemical ◽  
Interdisciplinary Framework ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Compare And Contrast ◽  
Kinetics Of

Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for discussing these subcellular force generators, I first review the application of reaction coordinate diagrams to the mechanisms of simple chemical and enzyme-catalyzed reactions. My description of reaction coordinate diagrams of motors and polymer ratchets is simplified relative to the rigorous biophysical treatment found in many of the references that I use and cite, but I hope that the essay provides a valuable qualitative representation of the physical chemical parameters that underlie the generation of force and motility at molecular scales. In any case, I have found that this approach represents a useful interdisciplinary framework for understanding, researching, and teaching the basic molecular mechanisms by which motors contribute to fundamental cell biological processes.

scholarly journals Interaction of Melanin with Metal Ions Modulates Their Cytotoxic Potential

2021 ◽  
Author(s):  
Tadeusz Sarna ◽  
Harold M. Swartz ◽  
Andrzej Zadlo
Keyword(s):  
Metal Ions ◽  
Biological Function ◽  
Melanin Granule ◽  
Redox Activation ◽  
Redox Active ◽  
Active Metal ◽  
Physicochemical Methods ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Redox Active Metal

AbstractMelanin is one the most common biological pigments. In humans, specialized cells called melanocytes synthesize the pigment from tyrosine and 3,4-dihydroxyphenylalanine via enzyme-catalyzed reactions and spontaneous processes. The formed melanin granule consists of nanoaggregates of oligomers containing different monomers. Although the main biological function of melanin is protection against damage from solar radiation, melanin may also be involved in protection against oxidative stress. In the latter function, sequestration of redox-active metal ions and scavenging of reactive oxygen species are of importance. The paper reviews basic physicochemical properties of melanin responsible for binding of metal ions and discusses specific conditions that may induce cytotoxicity of metal ions such as iron and copper by facilitating their redox activation and release from melanin. While the value of EPR spectroscopy and other EPR-related techniques for the study of melanin is emphasized, the concomitant use of other physicochemical methods is the most efficient approach.

Effect of metal ions on high-affinity binding of pseudosubstrate inhibitors to PKA

2008 ◽  
Vol 413 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Bastian Zimmermann ◽  
Sonja Schweinsberg ◽  
Stephan Drewianka ◽  
Friedrich W. Herberg
Keyword(s):  
Protein Kinase ◽  
Metal Ions ◽  
Metal Binding ◽  
Molecular Mechanisms ◽  
Regulatory Subunit ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity ◽  
C Subunit ◽  
Pseudosubstrate Inhibitors

Conformational control of protein kinases is an important way of modulating catalytic activity. Crystal structures of the C (catalytic) subunit of PKA (protein kinase A) in complex with physiological inhibitors and/or nucleotides suggest a highly dynamic process switching between open and more closed conformations. To investigate the underlying molecular mechanisms, SPR (surface plasmon resonance) was used for detailed binding analyses of two physiological PKA inhibitors, PKI (heat-stable protein kinase inhibitor) and a truncated form of the R (regulatory) subunit (RIα 92–260), in the presence of various concentrations of metals and nucleotides. Interestingly, it could be demonstrated that high-affinity binding of each pseudosubstrate inhibitor was dependent only on the concentration of divalent metal ions. At low micromolar concentrations of Mg2+ with PKI, transient interaction kinetics with fast on- and off-rates were observed, whereas at high Mg2+ concentrations the off-rate was slowed down by a factor of 200. This effect could be attributed to the second, low-affinity metal-binding site in the C subunit. In contrast, when investigating the interaction of RIα 92–260 with the C subunit under the same conditions, it was shown that the association rate rather than the dissociation rate was influenced by the presence of high concentrations of Mg2+. A model is presented, where the high-affinity interaction of the C subunit with pseudosubstrate inhibitors (RIα and PKI) is dependent on the closed, catalytically inactive conformation induced by the binding of a nucleotide complex where both of the metal-binding sites are occupied.

scholarly journals Metal Ions in Neuroscience

1997 ◽  
Vol 4 (3) ◽  
pp. 125-132 ◽  
Author(s):  
C. Ian Ragan
Keyword(s):  
Metal Ions ◽  
Metal Binding ◽  
Molecular Mechanisms ◽  
Bipolar Affective Disorder ◽  
Good Evidence ◽  
Convincing Evidence ◽  
Oxygen Species ◽  
Radical Species ◽  
Intracellular Signalling Pathway ◽  
Excitotoxic Cell Death

Metal ions are believed to participate in many neurodegenerative conditions. In excitotoxic cell death there is convincing evidence for the participation of Ca2+ and Zn2+ ions although the exact molecular mechanisms by which these metals exert their effects are unclear. Only in one instance has the metal binding site of metalloenzymes been exploited for therapeutic purposes and this is the use of Li+ in the treatment of bipolar affective disorder. Again the exact molecular target is not clear but is likely to involve a Mg2+-dependent enzyme of an intracellular signalling pathway. In Parkinson's disease, the selective loss of dopaminergic neurones in the substantia nigra may be caused by radical-mediated damage and there is good evidence to suggest that Fe2+ or 3+ is important in promoting formation of radical species. The evidence that free radicals are important in mediating other neurodegenerative conditions is less strong but still substantial enough to suggest that removal of reactive oxygen species or preventing their formation may be a valid approach to therapy.

Current Development of Metal Complexes with Diamine Ligands as Potential Anticancer Agents

2020 ◽  
Vol 27 (3) ◽  
pp. 380-410 ◽  
Author(s):  
Sonja Misirlic-Dencic ◽  
Jelena Poljarevic ◽  
Andjelka M. Isakovic ◽  
Tibor Sabo ◽  
Ivanka Markovic ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Complexes ◽  
Anticancer Agents ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Organic Ligand ◽  
Aromatic Diamine ◽  
Anticancer Efficacy ◽  
Anticancer Mechanism ◽  
Diamine Ligands

Background:: The discovery of cisplatin and the subsequent research revealed the importance of dinitrogen-containing moiety for the anticancer action of metal complexes. Moreover, certain diamine ligands alone display cytotoxicity that contributes to the overall activity of corresponding complexes. Objective:: To summarize the current knowledge on the anticancer efficacy, selectivity, and the mechanisms of action of metal complexes with various types of diamine ligands. Method:: The contribution of aliphatic acyclic, aliphatic cyclic, and aromatic diamine ligands to the anticancer activity and selectivity/toxicity of metal complexes with different metal ions were analyzed by comparison with organic ligand alone and/or conventional platinum-based chemotherapeutics. Results:: The aliphatic acyclic diamine ligands are present mostly in complexes with platinum. Aliphatic cyclic diamines are part of Pt(II), Ru(II) and Au(III) complexes, while aromatic diamine ligands are found in Pt(II), Ru(II), Pd(II) and Ir(III) complexes. The type and oxidation state of metal ions greatly influences the cytotoxicity of metal complexes with aliphatic acyclic diamine ligands. Lipophilicity of organic ligands, dependent on alkyl-side chain length and structure, determines their cellular uptake, with edda and eddp/eddip ligands being most useful in this regard. Aliphatic cyclic diamine ligands improved the activity/toxicity ratio of oxaliplatin-type complexes. The complexes with aromatic diamine ligands remain unexplored regarding their anticancer mechanism. The investigated complexes mainly caused apoptotic or necrotic cell death. Conclusion:: Metal complexes with diamine ligands are promising candidates for efficient and more selective alternatives to conventional platinum-based chemotherapeutics. Further research is required to reveal the chemico-physical properties and molecular mechanisms underlying their biological activity.

Key Elements of Gingival Epithelial Homeostasis upon Bacterial Interaction

2020 ◽  
pp. 002203452097301
Author(s):  
J.S. Lee ◽  
Ö. Yilmaz
Keyword(s):  
Epithelial Cells ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Functional Roles ◽  
Gingival Epithelial Cell ◽  
Opportunistic Bacteria ◽  
Gingival Epithelial Cells ◽  
Diseased State ◽  
Gingival Mucosa ◽  
External Stimuli

Epithelia are structurally integral elements in the fabric of oral mucosa with significant functional roles. Similarly, the gingival epithelium performs uniquely critical tasks in responding to a variety of external stimuli and dangers through the regulation of specific built-in molecular mechanisms in a context-dependent fashion at cellular levels. Gingival epithelial cells form an anatomic architecture that confers defense, robustness, and adaptation toward external aggressions, most critically to colonizing microorganisms, among other functions. Accordingly, recent studies unraveled previously uncharacterized response mechanisms in gingival epithelial cells that are constructed to rapidly exert biocidal effects against invader pathobiotic bacteria, such as Porphyromonas gingivalis, through small danger molecule signaling. The host-adapted bacteria, however, have developed adroit strategies to 1) exploit the epithelia as privileged growth niches and 2) chronically target cellular bactericidal and homeostatic metabolic pathways for successful bacterial persistence. As the overgrowth of colonizing microorganisms in the gingival mucosa can shift from homeostasis to dysbiosis or a diseased state, it is crucial to understand how the innate modulatory molecules are intricately involved in antibacterial pathways and how they shape susceptibility versus resistance in the epithelium toward pathogens. Thus, in this review, we highlight recent discoveries in gingival epithelial cell research in the context of bacterial colonizers. The current knowledge outlined here demonstrates the ability of epithelial cells to possess highly organized defense machineries, which can jointly regulate host-derived danger molecule signaling and integrate specific global responses against opportunistic bacteria to combat microbial incursion and maintain host homeostatic balance. These novel examples collectively suggest that the oral epithelia are equipped with a dynamically robust and interconnected defense system encompassing sensors and various effector molecules that arrange and achieve a fine-tuned and advanced response to diverse bacteria.

Mesophyll conductance: the leaf corridors for photosynthesis

2020 ◽  
Vol 48 (2) ◽  
pp. 429-439 ◽  
Author(s):  
Jorge Gago ◽  
Danilo M. Daloso ◽  
Marc Carriquí ◽  
Miquel Nadal ◽  
Melanie Morales ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Main Role ◽  
Mesophyll Conductance ◽  
Future Studies ◽  
Cell Structures ◽  
Leaf Tissues ◽  
Change Framework ◽  
Chloroplast Stroma

Besides stomata, the photosynthetic CO2 pathway also involves the transport of CO2 from the sub-stomatal air spaces inside to the carboxylation sites in the chloroplast stroma, where Rubisco is located. This pathway is far to be a simple and direct way, formed by series of consecutive barriers that the CO2 should cross to be finally assimilated in photosynthesis, known as the mesophyll conductance (gm). Therefore, the gm reflects the pathway through different air, water and biophysical barriers within the leaf tissues and cell structures. Currently, it is known that gm can impose the same level of limitation (or even higher depending of the conditions) to photosynthesis than the wider known stomata or biochemistry. In this mini-review, we are focused on each of the gm determinants to summarize the current knowledge on the mechanisms driving gm from anatomical to metabolic and biochemical perspectives. Special attention deserve the latest studies demonstrating the importance of the molecular mechanisms driving anatomical traits as cell wall and the chloroplast surface exposed to the mesophyll airspaces (Sc/S) that significantly constrain gm. However, even considering these recent discoveries, still is poorly understood the mechanisms about signaling pathways linking the environment a/biotic stressors with gm responses. Thus, considering the main role of gm as a major driver of the CO2 availability at the carboxylation sites, future studies into these aspects will help us to understand photosynthesis responses in a global change framework.

A kinetic analysis of coupled sequential enzyme reactions

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Santiago Schnell
Keyword(s):  
Enzyme Assay ◽  
Sequential Reaction ◽  
Enzyme Reactions ◽  
Indicator Reaction ◽  
Single Substrate ◽  
Complex Sequences ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions ◽  
Single Enzyme

<div>As a case study, we consider a coupled enzyme assay of sequential enzyme reactions obeying the Michaelis--Menten reaction mechanism. The sequential reaction consists of a single-substrate, single-enzyme non-observable reaction followed by another single-substrate, single-enzyme observable reaction (indicator reaction). In this assay, the product of the non-observable reaction becomes the substrate of the indicator reaction. A mathematical analysis of the reaction kinetics is performed, and it is found that after an initial fast transient, the sequential reaction is described by a pair of interacting Michaelis--Menten equations. Timescales that approximate the respective lengths of the indicator and non-observable reactions, as well as conditions for the validity of the Michaelis--Menten equations are derived. The theory can be extended to deal with more complex sequences of enzyme catalyzed reactions.</div>

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