scholarly journals Review of Mutarotase in ‘Metabolic Subculture’ and Analytical Biochemistry: Prelude to 19F NMR Studies of its Substrate Specificity and Mechanism

2020 ◽  
Vol 73 (3) ◽  
pp. 112
Author(s):  
Dmitry Shishmarev ◽  
Lucas Quiquempoix ◽  
Clément Q. Fontenelle ◽  
Bruno Linclau ◽  
Philip W. Kuchel
Keyword(s):  
Substrate Specificity ◽  
Molecular Mechanism ◽  
Active Site ◽  
Current Knowledge ◽  
Experimental Studies ◽  
Physiological Role ◽  
19F Nmr ◽  
Nmr Studies ◽  
Glucose Analogues

This is the first paper in a sequential pair devoted to the enzyme mutarotase (aldose 1-epimerase; EC 5.1.3.3). Here, the broader context of the physiological role of mutarotase, among those enzymes considered to be part of ‘metabolic structure’, is reviewed. We also summarise the current knowledge about the molecular mechanism and substrate specificity of the enzyme, which is considered in the context of the binding of fluorinated glucose analogues to the enzyme’s active site. This was done as a prelude to our experimental studies of the anomerisation of fluorinated sugars by mutarotase that are described in the following paper.

scholarly journals Regulatory T Cell-Enhancing Therapies to Treat Atherosclerosis

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 723
Author(s):  
Hafid Ait-Oufella ◽  
Jean-Rémi Lavillegrand ◽  
Alain Tedgui
Keyword(s):  
T Cell ◽  
Current Knowledge ◽  
Experimental Studies ◽  
Therapeutic Approaches ◽  
Coronary Patients ◽  
Cell Subpopulations ◽  
Atherosclerotic Process ◽  
T Cell Subpopulations ◽  
Disease Analysis

Experimental studies have provided strong evidence that chronic inflammation triggered by the sub-endothelial accumulation of cholesterol-rich lipoproteins in arteries is essential in the initiation and progression of atherosclerosis. Recent clinical trials highlighting the efficacy of anti-inflammatory therapies in coronary patients have confirmed that this is also true in humans Monocytes/macrophages are central cells in the atherosclerotic process, but adaptive immunity, through B and T lymphocytes, as well as dendritic cells, also modulates the progression of the disease. Analysis of the role of different T cell subpopulations in murine models of atherosclerosis identified effector Th1 cells as proatherogenic, whereas regulatory T cells (Tregs) have been shown to protect against atherosclerosis. For these reasons, better understanding of how Tregs influence the atherosclerotic process is believed to provide novel Treg-targeted therapies to combat atherosclerosis. This review article summarizes current knowledge about the role of Tregs in atherosclerosis and discusses ways to enhance their function as novel immunomodulatory therapeutic approaches against cardiovascular disease.

scholarly journals Probing the ionization state of substrate α-d-glucopyranosyl phosphate bound to glycogen phosphorylase b

1995 ◽  
Vol 308 (3) ◽  
pp. 1017-1023 ◽  
Author(s):  
I P Street ◽  
S G Withers
Keyword(s):  
Active Site ◽  
Glycogen Phosphorylase ◽  
Ph Dependence ◽  
Substrate Inhibition ◽  
19F Nmr ◽  
Ionization State ◽  
Nmr Studies ◽  
Substrate Analogues ◽  
Glycogen Phosphorylase B ◽  
Pka Value

The ionization state of the substrate alpha-D-glucopyranosyl phosphate bound at the active site of glycogen phosphorylase has been probed by a number of techniques. Values of Ki determined for a series of substrate analogue inhibitors in which the phosphate moiety bears differing charges suggest that the enzyme will bind both the monoanionic and dianionic substrates with approximately equal affinity. These results are strongly supported by 31P- and 19F-NMR studies of the bound substrate analogues alpha-D-glucopyranosyl 1-methylenephosphonate and 2-deoxy-2-fluoro-alpha-D-glucopyranosyl phosphate, which also suggest that the substrate can be bound in either ionization state. The pH-dependences of the inhibition constants K1 for these two analogues, which have substantially different phosphate pK2 values (7.3 and 5.9 respectively), are found to be essentially identical with the pH-dependence of K(m) values for the substrate, inhibition decreasing according to an apparent pKa value of 7.2. This again indicates that there is no specificity for monoanion or dianion binding and also reveals that binding is associated with the uptake of a proton. As the bound substrate is not protonated, this proton must be taken up by the proton.

scholarly journals Kinins and Kinin Receptors in Cardiovascular and Renal Diseases

2021 ◽  
Vol 14 (3) ◽  
pp. 240
Author(s):  
Jean-Pierre Girolami ◽  
Nadine Bouby ◽  
Christine Richer-Giudicelli ◽  
Francois Alhenc-Gelas
Keyword(s):  
Experimental Studies ◽  
Physiological Role ◽  
Renal Diseases ◽  
Kinin System ◽  
Genetic Studies ◽  
Pharmacological Manipulation ◽  
Kininase Ii ◽  
Kinin Receptors ◽  
Kallikrein Kinin System

This review addresses the physiological role of the kallikrein–kinin system in arteries, heart and kidney and the consequences of kallikrein and kinin actions in diseases affecting these organs, especially ischemic and diabetic diseases. Emphasis is put on pharmacological and genetic studies targeting kallikrein; ACE/kininase II; and the two kinin receptors, B1 (B1R) and B2 (B2R), distinguished through the work of Domenico Regoli and his collaborators. Potential therapeutic interest and limitations of the pharmacological manipulation of B1R or B2R activity in cardiovascular and renal diseases are discussed. This discussion addresses either the activation or inhibition of these receptors, based on recent clinical and experimental studies.

scholarly journals The Neuroinflammatory Role of Pericytes in Epilepsy

Biomedicines ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 759
Author(s):  
Gaku Yamanaka ◽  
Fuyuko Takata ◽  
Yasufumi Kataoka ◽  
Kanako Kanou ◽  
Shinichiro Morichi ◽  
...  
Keyword(s):  
Proinflammatory Cytokines ◽  
Current Knowledge ◽  
Morphological Changes ◽  
Cell Damage ◽  
Neurovascular Unit ◽  
Experimental Studies ◽  
Intractable Epilepsy ◽  
In Vivo Studies

Pericytes are a component of the blood–brain barrier (BBB) neurovascular unit, in which they play a crucial role in BBB integrity and are also implicated in neuroinflammation. The association between pericytes, BBB dysfunction, and the pathophysiology of epilepsy has been investigated, and links between epilepsy and pericytes have been identified. Here, we review current knowledge about the role of pericytes in epilepsy. Clinical evidence has shown an accumulation of pericytes with altered morphology in the cerebral vascular territories of patients with intractable epilepsy. In vitro, proinflammatory cytokines, including IL-1β, TNFα, and IL-6, cause morphological changes in human-derived pericytes, where IL-6 leads to cell damage. Experimental studies using epileptic animal models have shown that cerebrovascular pericytes undergo redistribution and remodeling, potentially contributing to BBB permeability. These series of pericyte-related modifications are promoted by proinflammatory cytokines, of which the most pronounced alterations are caused by IL-1β, a cytokine involved in the pathogenesis of epilepsy. Furthermore, the pericyte-glial scarring process in leaky capillaries was detected in the hippocampus during seizure progression. In addition, pericytes respond more sensitively to proinflammatory cytokines than microglia and can also activate microglia. Thus, pericytes may function as sensors of the inflammatory response. Finally, both in vitro and in vivo studies have highlighted the potential of pericytes as a therapeutic target for seizure disorders.

scholarly journals Role of Mitochondrial Cytochrome P450 2E1 in Healthy and Diseased Liver

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 288
Author(s):  
Julie Massart ◽  
Karima Begriche ◽  
Jessica H. Hartman ◽  
Bernard Fromenty
Keyword(s):  
Oxidative Stress ◽  
Cytochrome P450 ◽  
Liver Disease ◽  
Fatty Liver ◽  
Current Knowledge ◽  
Physiological Role ◽  
Experimental Investigations ◽  
Rat Liver Mitochondria ◽  
Cytochrome P450 2E1

Cytochrome P450 2E1 (CYP2E1) is pivotal in hepatotoxicity induced by alcohol abuse and different xenobiotics. In this setting, CYP2E1 generates reactive metabolites inducing oxidative stress, mitochondrial dysfunction and cell death. In addition, this enzyme appears to play a role in the progression of obesity-related fatty liver to nonalcoholic steatohepatitis. Indeed, increased CYP2E1 activity in nonalcoholic fatty liver disease (NAFLD) is deemed to induce reactive oxygen species overproduction, which in turn triggers oxidative stress, necroinflammation and fibrosis. In 1997, Avadhani’s group reported for the first time the presence of CYP2E1 in rat liver mitochondria, and subsequent investigations by other groups confirmed that mitochondrial CYP2E1 (mtCYP2E1) could be found in different experimental models. In this review, we first recall the main features of CYP2E1 including its role in the biotransformation of endogenous and exogenous molecules, the regulation of its expression and activity and its involvement in different liver diseases. Then, we present the current knowledge on the physiological role of mtCYP2E1, its contribution to xenobiotic biotransformation as well as the mechanism and regulation of CYP2E1 targeting to mitochondria. Finally, we discuss experimental investigations suggesting that mtCYP2E1 could have a role in alcohol-associated liver disease, xenobiotic-induced hepatotoxicity and NAFLD.

Ammonium transport: unifying concepts and unique aspects

2001 ◽  
Vol 28 (9) ◽  
pp. 959 ◽  
Author(s):  
Anne van Dommelen ◽  
René de Mot ◽  
Jos Vanderleyden
Keyword(s):  
Current Knowledge ◽  
Natural Habitat ◽  
Physiological Role ◽  
Ammonium Uptake ◽  
Ammonium Transport ◽  
Symbiotic Interaction ◽  
Ammonium Transporters ◽  
Operating Current ◽  
Living Organisms

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Ammonium uptake by cells has been studied for more than a century, but only recently a family of ammonium transporters (Mep/Amt) with 10–12 transmembrane domains has been defined. These proteins are probably ubiquitous, since homologues have been found in the major kingdoms of living organisms. Plants as well as yeast and some archaebacteria have multiple Mep/Amt paralogues, which can be distinguished by their affinity for ammonium and the ammonium analogue methylammonium. Most ammonium transporters are induced in nitrogen-starving conditions, both in prokaryotes and plants. In Saccharomyces cerevisiae, Escherichia coli and Azospirillum brasilense Mep/Amt proteins where shown to be necessary for growth when the external concentration of the diffusive ammonium form (NH3) becomes limiting. Ammonium transporters also play an important role in pseudohyphal differentiation in yeast and efficient symbiotic interaction between Rhizobium etli and its host plant. In most bacteria, NH4+ transport appears to be a uniport mechanism driven by the membrane potential, but, depending on the organism, a different mode of ammonium uptake may be operating. Current knowledge offers the basis to investigate further the physiological role of ammonium transporters in the natural habitat of organisms and their importance in plant–bacteria interactions.

scholarly journals Re-examination of the roles of PEP and Mg2+ in the reaction catalysed by the phosphorylated and non-phosphorylated forms of phosphoenolpyruvate carboxylase from leaves of Zea mays

1998 ◽  
Vol 332 (3) ◽  
pp. 633-642 ◽  
Author(s):  
Alejandro TOVAR-MÉNDEZ ◽  
Rogelio RODRÍGUEZ-SOTRES ◽  
Dulce M. LÓPEZ-VALENTÍN ◽  
Rosario A. MUÑOZ-CLARES
Keyword(s):  
Active Site ◽  
Phosphoenolpyruvate Carboxylase ◽  
Metal Ion ◽  
Dissociation Constants ◽  
Physiological Role ◽  
Free Enzyme ◽  
Kinetic Properties ◽  
Allosteric Site ◽  
Physiological Concentration

To study the effects of phosphoenolpyruvate (PEP) and Mg2+ on the activity of the non-phosphorylated and phosphorylated forms of phosphoenolpyruvate carboxylase (PEPC) from Zea maysleaves, steady-state measurements have been carried out with the free forms of PEP (fPEP) and Mg2+ (fMg2+), both in a near-physiological concentration range. At pH 7.3, in the absence of activators, the initial velocity data obtained with both forms of the enzyme are consistent with the exclusive binding of MgPEP to the active site and of fPEP to an activating allosteric site. At pH 8.3, and in the presence of saturating concentrations of glucose 6-phosphate (Glc6P) or Gly, the free species also combined with the active site in the free enzyme, but with dissociation constants at least 35-fold that estimated for MgPEP. The latter dissociation constant was lowered to the same extent by saturating Glc6P and Gly, to approx. one-tenth and one-sixteenth in the non-phosphorylated and phosphorylated enzymes respectively. When Glc6P is present, fPEP binds to the active site in the free enzyme better than fMg2+, whereas the metal ion binds better in the presence of Gly. Saturation of the enzyme with Glc6P abolished the activation by fPEP, consistent with a common binding site, whereas saturation with Gly increased the affinity of the allosteric site for fPEP. Under all the conditions tested, our results suggest that fPEP is not able to combine with the allosteric site in the free enzyme, i.e. it cannot combine until after MgPEP, fPEP or fMg2+ are bound at the active site. The physiological role of Mg2+ in the regulation of the enzyme is only that of a substrate, mainly as part of the MgPEP complex. The kinetic properties of maize leaf PEPC reported here are consistent with the enzyme being well below saturation under the physiological concentrations of fMg2+ and PEP, particularly during the dark period; it is therefore suggested that the basal PEPC activity in vivois very low, but highly responsive to even small changes in the intracellular concentration of its substrate and effectors.

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