RESUMEN
A series of N-substituted amide linked triazolyl ß-d-glucopyranoside derivatives (4a-l) were synthesized and their in vitro inhibitory activity against yeast α-glucosidase enzyme [EC.3.2.1.20] was assessed. Compounds 4e (IC50=156.06µM), 4f (IC50=147.94µM), 4k (IC50=127.71µM) and 4l (IC50=121.33µM) were identified as the most potent inhibitors for α-glucosidase as compared to acarbose (IC50=130.98µM) under the same in vitro experimental conditions. Kinetic study showed that both 4e and 4f inhibit the enzyme in a competitive manner with p-nitrophenyl α-d-glucopyranoside as substrate. Molecular docking studies of 4e, 4f, 4k and 4l were also carried out using homology model of α-glucosidase to find out the binding modes responsible for the inhibitory activity. This study revealed that the binding affinity of compounds 4e, 4f, 4k and 4l for α-glucosidase were -8.2, -8.6, -8.3 and -8.5kcal/mol respectively, compared to that of acarbose (-8.9kcal/mol). The results suggest that the N-substituted amide linked triazole glycoconjugates can reasonably mimic the substrates for the yeast α-glucosidase.
Asunto(s)
Amidas/farmacología , Glicoconjugados/farmacología , Inhibidores de Glicósido Hidrolasas/farmacología , Simulación del Acoplamiento Molecular , alfa-Glucosidasas/metabolismo , Amidas/química , Relación Dosis-Respuesta a Droga , Glicoconjugados/síntesis química , Glicoconjugados/química , Inhibidores de Glicósido Hidrolasas/síntesis química , Inhibidores de Glicósido Hidrolasas/química , Humanos , Estructura Molecular , Relación Estructura-ActividadRESUMEN
Human C-reactive protein (CRP), as a mediator of innate immunity, removed damaged cells by activating the classical complement pathway. Previous studies have successfully demonstrated that CRPs are differentially induced as glycosylated molecular variants in certain pathological conditions. Affinity-purified CRPs from two most prevalent diseases in India viz. tuberculosis (TB) and visceral leishmaniasis (VL) have differential glycosylation in their sugar composition and linkages. As anemia is a common manifestation in TB and VL, we assessed the contributory role of glycosylated CRPs to influence hemolysis via CRP-complement-pathway as compared to healthy control subjects. Accordingly, the specific binding of glycosylated CRPs with erythrocytes was established by flow-cytometry and ELISA. Significantly, deglycosylated CRPs showed a 7-8-fold reduced binding with erythrocytes confirming the role of glycosylated moieties. Scatchard analysis revealed striking differences in the apparent binding constants (10(4)-10(5) M(-1)) and number of binding sites (10(6)-10(7)sites/erythrocyte) for CRP on patients' erythrocytes as compared to normal. Western blotting along with immunoprecipitation analysis revealed the presence of distinct molecular determinants on TB and VL erythrocytes specific to disease-associated CRP. Increased fragility, hydrophobicity and decreased rigidity of diseased-erythrocytes upon binding with glycosylated CRP suggested membrane damage. Finally, the erythrocyte-CRP binding was shown to activate the CRP-complement-cascade causing hemolysis, even at physiological concentration of CRP (10 microg/ml). Thus, it may be postulated that CRP have a protective role towards the clearance of damaged-erythrocytes in these two diseases.
Asunto(s)
Proteína C-Reactiva/inmunología , Activación de Complemento/inmunología , Eritrocitos/inmunología , Hemólisis/inmunología , Leishmaniasis Visceral/inmunología , Tuberculosis/inmunología , Adulto , Proteína C-Reactiva/química , Secuencia de Carbohidratos , Membrana Eritrocítica/inmunología , Citometría de Flujo , Fluoresceína-5-Isotiocianato/metabolismo , Glicosilación , Humanos , India , Proteínas de la Membrana/metabolismo , Persona de Mediana Edad , Datos de Secuencia Molecular , Unión Proteica , Resonancia por Plasmón de Superficie , Adulto JovenRESUMEN
The lipopolysaccharide (LPS) of the Gram-negative Acidiphilium strain GS18h/ATCC55963, a new soil isolate, exhibited very low endotoxic activity as determined by Limulus gelation activity, lethal toxicity in galactosamine (GalN) sensitised mice, and level of tumor necrosis factor alpha (TNFalpha) in the blood serum of BALB/c mice. Analysis of the LPS, specially of lipid A which usually accounts for the toxicity, revealed the latter to contain glucosamine and phosphate besides fatty acids, of which 14:0(3-OH), 18:0(3-OH), 18:1 and 19:0(cyclo) are the major components, while 12:0, 16:0, 19:1, 20:0(3-OH) and 20:1(3-OH) are present in small amounts. The 14:0(3-OH) and 18:0(3-OH) fatty acids are amide-linked, whereas the rest are ester bound. Glucose, galactose, mannose, rhamnose, heptose, galacturonic acid and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) were present in the polysaccharide part of this LPS. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the LPS showed a macromolecular heterogeneity distinctly different from those of Escherichia coli or Salmonella. The toxicity of this LPS being extremely low attributed to fatty acid composition of its lipid A, promises potential therapeutic application.
Asunto(s)
Acidiphilium/metabolismo , Lipopolisacáridos , Microbiología del Suelo , Acidiphilium/aislamiento & purificación , Animales , Cobre , Cangrejos Herradura , India , Lípido A/análisis , Lipopolisacáridos/administración & dosificación , Lipopolisacáridos/química , Lipopolisacáridos/aislamiento & purificación , Lipopolisacáridos/toxicidad , Ratones , Ratones Endogámicos BALB C , Minería , Factor de Necrosis Tumoral alfa/biosíntesisRESUMEN
Earlier studies have demonstrated an over-expression of 9-O-acetylated sialoglycoconjugates (9-OAcSGs) on lymphoblasts, concomitant with high titers of anti-9-OAcSGs in childhood acute lymphoblastic leukemia (ALL). The present study was aimed to evaluate whether this high induction of anti-9-OAcSGs at disease presentation contributes toward immune surveillance. Accordingly, anti-9-OAcSGs were affinity purified from sera of ALL patients and normal individuals, and their specificity toward the glycotope having terminal 9-O-acetylated sialic acid-linked subterminal N-acetyl galactosamine (GalNAc) in alpha2-6 manner (9-OAcSAalpha2-6GalNAc) was established by hemagglutination assay, flow cytometry and confocal microscopy. Subclass distribution of anti-9-OAcSGs revealed a predominance of IgG2 in ALL. Analysis of glycosylation of anti-9-OAcSGs purified from sera of ALL patients (IgG(ALL)) and normal individuals (IgG(N)) by digoxigenin glycan enzyme assay, fluorimetric estimation, gas-liquid chromatography and lectin-binding assays demonstrated that disease-specific antibodies differ in content and nature as compared with normal controls. Enhanced amount of 9-OAcSA-specific IgG2 induced in ALL was unable to trigger activation of FcgammaR, the complement cascade and cell-mediated cytotoxicity, although its glycotope-binding ability remains unaffected. Interestingly, only IgG1N emerged as the potent mediator of cell-mediated cytotoxicity, complement fixation and activator of effector cells through FcgammaR. In ALL, the observed subclass switching of anti-9-OAcSGs to IgG2, alteration in their glycosylation profile along with impairment of a few Fc-glycosylation-sensitive effector functions hints toward a disbalanced homeostasis, thereby evading the host defense. These findings justify further evaluation of the mechanism for functional unresponsiveness of antibodies and production of 9-OAcSA-specific chimeric antibodies with normal Fc domain for therapeutic applications.