Inhibition of CpLIP2 Lipase Hydrolytic Activity by Four Flavonols (Galangin, Kaempferol, Quercetin, Myricetin) Compared to Orlistat and Their Binding Mechanisms Studied by Quenching of Fluorescence

The inhibition of recombinant CpLIP2 lipase/acyltransferase from Candida parapsiolosis was considered a key model for novel antifungal drug discovery and a potential therapeutic target for candidiasis. Lipases have identified recently as potent virulence factors in C. parapsilosis and some other yeasts. The inhibition effects of orlistat and four flavonols (galangin, kaempferol, quercetin and myricetin) characterized by an increasing degree of hydroxylation in B-ring, were investigated using ethyl oleate hydrolysis as the model reaction. Orlistat and kaempferol (14 µM) strongly inhibited CpLIP2 catalytic activity within 1 min of pre-incubation, by 90% and 80%, respectively. The relative potency of flavonols as inhibitors was: kaempferol > quercetin > myricetin > galangin. The results suggested that orlistat bound to the catalytic site while kaempferol interacted with W294 on the protein lid. A static mechanism of interactions between flavonols and CpLIP2 lipase was confirmed by fluorescence quenching analyses, indicating that the interactions were mainly driven by hydrophobic bonds and electrostatic forces. From the Lehrer equation, fractions of tryptophan accessibility to the quencher were evaluated, and a relationship with the calculated number of binding sites was suggested.

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The Estimation of the Number of Binding Sites for Antibody on Antigen Molecules with Reference to Factor VIII and its Antibody

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647956 ◽

1976 ◽

Vol 35 (02) ◽

pp. 274-288 ◽

Cited By ~ 2

Author(s):

Judith Pool ◽

Rosemary Biggs ◽

R. G Miller

Keyword(s):

Factor Viii ◽

Binding Sites ◽

Theoretical Basis ◽

Human Antibody ◽

Rabbit Antibody ◽

Number Of Binding Sites ◽

Theoretical Considerations

SummaryThe theoretical basis for determining the number of antibody sites on antigen molecules is examined. The theoretical considerations are applied to factor VIII molecules. Examples based on data available at the Oxford Haemophilia Centre are calculated to illustrate the approach. It is concluded that there are few sites on each factor VIII molecule for human antibody. The three antibodies for which reasonable data were available suggest 1–3 sites for human antibody. The data for rabbit antibody suggest 5–6 sites per factor VIII molecule.

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Abnormal Platelet Serotonin Uptake and Binding Sites in Myeloproliferative Disorders

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661099 ◽

1984 ◽

Vol 51 (03) ◽

pp. 349-353 ◽

Cited By ~ 9

Author(s):

C Caranobe ◽

P Sié ◽

F Fernandez ◽

J Pris ◽

S Moatti ◽

...

Keyword(s):

Binding Sites ◽

High Capacity ◽

Specific Inhibitor ◽

Myeloproliferative Disorders ◽

Normal Subjects ◽

Binding Data ◽

Full Explanation ◽

Number Of Binding Sites ◽

5 Ht Uptake ◽

Kinetics Of

SummaryA simultaneous investigation of the kinetics of serotonin (5 HT) uptake and of binding sites was carried out in the platelets of normal subjects and of 10 patients affected with various types of myeloproliferative disorders (MD). The 5 HT uptake was analysed according to the Lineweaver-Burk and the Eadie-Hofstee methods. With the two methods, the patient’s platelets exhibited a dramatic reduction of the Vi max and of the Km; in some patients the Eadie-Hofstee analysis revealed that a passive diffusion phenomenon is superimposed on the active 5 HT uptake at least for the higher concentration used. The binding data were analysed with the Scatchard method. Two classes of binding sites (high affinity - low capacity, low affinity - high capacity) were found in normal subjects and patients. Pharmacological studies with imipramine, a specific inhibitor of 5 HT uptake, suggested that both the sites are involved in 5 HT uptake. The number of both binding sites was significantly decreased in patient’s platelets while the affinity constants of these binding sites were not significantly reduced in comparison with those of the control subjects. No correlations were found between Vi max, Km and the number of binding sites. These results suggest that a reduction in the number of platelet membrane acceptors for 5 HT commonly occurs in myeloproliferative disorders but does not provide a full explanation of the uptake defect.

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Effects of cations on binding of human choriogonadotropin

Biochemistry and Cell Biology ◽

10.1139/o88-145 ◽

1988 ◽

Vol 66 (12) ◽

pp. 1258-1264

Author(s):

Patrick J. McIlroy

Keyword(s):

Binding Sites ◽

Regulatory Protein ◽

Guanine Nucleotides ◽

Guanine Nucleotide ◽

Human Choriogonadotropin ◽

Receptor Sites ◽

Number Of Binding Sites ◽

Receptor Number ◽

Guanine Nucleotide Regulatory Protein ◽

Low Ionic Strength

The effect of various salts on the binding of human choriogonadotropin to rat luteal membranes has been examined. Increasing salt concentrations had biphasic effects, initially increasing binding, then decreasing it. With NaCl, these effects were on both the affinity and the number of receptor sites. The affinity increased with increasing NaCl concentrations, to a maximum at 40 mM, and then decreased. Above 40 mM NaCl, the number of binding sites increased. NaCl also altered the effects of Mg2+ and guanyl nucleotides. At low ionic strength, Mg2+ was necessary to observe binding. Guanine nucleotides modulated this binding by decreasing the affinity. At 40 mM NaCl, Mg2+ increased receptor number without altering affinity. Guanyl nucleotides modulated this binding by reducing the number of sites to that observed in the absence of Mg2+. At 150 mM NaCl, Mg2+ and guanine nucleotides had no effect. The results suggest the presence of two pools of human choriogonadotropin receptor in rat corpus luteum, one coupled to the guanine nucleotide regulatory protein (Ns) and being Mg2+ dependent and guanine nucleotide sensitive, and the other not coupled to Ns and being Mg2+ independent and guanine nucleotide insensitive.

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Studies on synthetic peptides that bind to fibrinogen and prevent fibrin polymerization. Structural requirements, number of binding sites, and species differences

Biochemistry ◽

10.1021/bi00546a028 ◽

1980 ◽

Vol 19 (5) ◽

pp. 1013-1019 ◽

Cited By ~ 195

Author(s):

Andrew P. Laudano ◽

Russell F. Doolittle

Keyword(s):

Binding Sites ◽

Synthetic Peptides ◽

Species Differences ◽

Structural Requirements ◽

Fibrin Polymerization ◽

Number Of Binding Sites

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Somatostatin levels and binding in duodenal mucosa of rabbits with ligation of the pancreatic duct

Journal of Endocrinology ◽

10.1677/joe.0.1180227 ◽

1988 ◽

Vol 118 (2) ◽

pp. 227-232 ◽

Cited By ~ 2

Author(s):

L. G. Guijarro ◽

E. Arilla

Keyword(s):

Pancreatic Duct ◽

Binding Sites ◽

Exocrine Pancreas ◽

Duodenal Mucosa ◽

Physiological Significance ◽

Scatchard Analysis ◽

Pancreatic Duct Ligation ◽

Parallel Increase ◽

Duct Ligation ◽

Number Of Binding Sites

ABSTRACT Atrophy of the exocrine pancreas was induced in rabbits by pancreatic duct ligation. Somatostatin concentration and binding in cytosol from rabbit duodenal mucosa were studied after 6 and 14 weeks of pancreatic duct ligation. Somatostatin-like immunoreactivity was significantly increased in the duodenal mucosa in both periods. Scatchard analysis showed a parallel increase in the number of binding sites rather than a change in their affinity. The physiological significance of these findings remains to be clarified. J. Endocr. (1988) 118, 227–232

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Spectroscopic Study of the Interactions of Ruthenium-Ketoconazole Complexes of Known Antiparasitic Activity with Human Serum Albumin and Apotransferrin

Journal of the Mexican Chemical Society ◽

10.29356/jmcs.v57i3.203 ◽

2017 ◽

Vol 57 (3) ◽

Cited By ~ 1

Author(s):

Jesús G. Estrada ◽

Roberto A. Sánchez-Delgado

Keyword(s):

Human Serum Albumin ◽

Serum Albumin ◽

Human Serum ◽

Leishmania Major ◽

Tryptophan Fluorescence ◽

Ru Complex ◽

Complex Protein ◽

Number Of Binding Sites ◽

Antiparasitic Drugs ◽

Static Mechanism

The pharmacological properties of any drug are related to its ability to interact with macromolecular blood components. The interaction of human serum albumin (HSA) and apotransferrin (ATf) with six RuII complexes containing ketoconazole (KTZ), which we have previously reported to be active against Leishmania major and Trypanosoma cruzi, has been investigated by monitoring the tryptophan fluorescence intensity of each protein upon incremental addition of the complexes. All the Ru-KTZ derivatives, namely cis-fac-[RuIICl2(DMSO)3(KTZ)] (1), cis-[RuIICl2(bipy)(DMSO)(KTZ)] (2), [RuII(η6-p-cymene)Cl2(KTZ)] (3), [RuII(η6-p-cymene)(en)(KTZ)][BF4]2 (4), [RuII(η6-p-cymene)(bipy)(KTZ)][BF4]2 (5), and [RuII(η6-p-cymene)(acac)(KTZ)][BF4] (6) are able to quench the intrinsic fluorescence of HSA and ATf at 27 ºC. Analysis of the spectroscopic data using Stern-Volmer plots indicates that in both cases the quenching takes place principally through a static mechanism involving the formation of Ru complex-protein adducts; further analysis of the fluorescence data allowed the estimation of apparent association constants and the number of binding sites for each protein and each compound. The results indicate that both HSA and ATf are possible effective transporters for Ru-KTZ antiparasitic drugs.

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Prostaglandin E2 receptors in the heart are coupled to inhibition of adenylyl cyclase via a pertussis toxin sensitive G protein

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y92-011 ◽

1992 ◽

Vol 70 (1) ◽

pp. 77-84 ◽

Cited By ~ 5

Author(s):

Richard W. Lerner ◽

Gary D. Lopaschuk ◽

Peter M. Olley

Keyword(s):

Adenylyl Cyclase ◽

G Protein ◽

Pertussis Toxin ◽

Binding Sites ◽

Cyclase Activity ◽

Prostaglandin E ◽

Adenylyl Cyclase Activity ◽

Adp Ribosylation ◽

Number Of Binding Sites ◽

Guanine Nucleotide Binding

In previous studies we have identified and isolated a prostaglandin E2 (PGE2) receptor from cardiac sarcolemmal (SL) membranes. Binding of PGE2 to this receptor in permeabilized SL vesicles inhibits adenylyl cyclase activity. The purpose of this study was to determine if the cardiac PGE2 receptor is coupled to adenylyl cyclase via a pertussis toxin sensitive guanine nucleotide binding inhibitory (Gi) protein. Incubation of permeabilized SL vesicles in the presence of 100 μM 5′-guanylamidiophosphate, Gpp(NH)p, a nonhydrolyzable analogue of GTP, resulted in a shift in [3H]PGE2 binding from two sites, one of high affinity (KD = 0.018 ± 0.003 nM) comprising 7.7% of the total available binding sites and one of lower affinity (KD = 1.9 ± 0.7 nM) to one site of intermediate affinity (KD = 0.52 ± 0.01 nM) without a significant change in the total number of PGE2 binding sites. A shift from two binding sites to one binding site in the presence of Gpp(NH)p was also observed for [3H]dihydroalprenolol binding to permeabilized cardiac SL. When permeabilized SL vesicles were pretreated with activated pertussis toxin, ADP-ribosylation of a 40- to 41-kDa protein corresponding to Gi was observed. ADP-ribosylation of SL resulted in a shift in [3H]PGE2 binding to one site of intermediate affinity without significantly changing the number of binding sites. In alamethicin permeabilized SL vesicles, 1 nM PGE2 significantly decreased (30%) adenylyl cyclase activity. Pretreatment with activated pertussis toxin overcame the inhibitory effects of PGE2. These results demonstrate that the cardiac PGE2 receptor is coupled to adenylyl cyclase via a pertussis toxin sensitive Gi protein. They also demonstrate that the interaction of this Gi protein with the PGE2 receptor is important in the regulation of PGE2 binding to its receptor.Key words: prostaglandin E2, sarcolemma, heart, adenylyl cyclase, G protein.

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Modulation by cholecystokinins of3H-spiroperidol binding in rat striatum: evidence for increased affinity and reduction in the number of binding sites

Acta Physiologica Scandinavica ◽

10.1111/j.1748-1716.1981.tb06942.x ◽

1981 ◽

Vol 113 (4) ◽

pp. 567-569 ◽

Cited By ~ 131

Author(s):

KJELL FUXE ◽

LUIGI F. AGNATI ◽

FABIO BENFENATI ◽

MAURO CIMMINO ◽

SILVIO ALGERI ◽

...

Keyword(s):

Binding Sites ◽

Rat Striatum ◽

Number Of Binding Sites

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Number of binding sites of rabbit macroglobulin antibody and its subunits

Molecular Immunology ◽

10.1016/0161-5890(65)90039-8 ◽

1965 ◽

Vol 2 (4) ◽

pp. 401-406

Author(s):

K Onoue

Keyword(s):

Binding Sites ◽

Number Of Binding Sites

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The Importance of the Carbohydrate Moiety of the Factor VIII/Von Willebrand Factor Protein in Binding to and Causing Agglutination of Human Platelets

10.1055/s-0039-1687415 ◽

1979 ◽

Author(s):

H.R. Gralnick ◽

D.K. Morisato

Keyword(s):

Factor Viii ◽

Von Willebrand Factor ◽

Binding Sites ◽

Human Platelets ◽

Galactose Oxidase ◽

Scatchard Analysis ◽

Human Fibrinogen ◽

Number Of Binding Sites ◽

Von Willebrand ◽

Willebrand Factor

We have investigated the binding of radiolabelled factor VIII/von Willebrand factor (f. VIII/vWf) protein to human platelets (P) in the presence of ristocetin (R). In these atudies we have delineated the importance of the carbohydrate (CHO) moiety(s) in both the binding to the P and in cauaing agglutination of P. Binding of the f.VIII/vWf protein to human P was time and temperature dependent and dependent on the concentration of R. Binding was specific in that it could not be blocked by human fibrinogen but was inhibited by unlabelled f.VIII/vWf protein. In studies utilizing varying amounts of the f.VIII/vWf protein or by varying the number of P in the assay, the number of binding sites for the f. VIII/vWf protein were estimated at 9,500-9,800 per platelet. Scatchard analysis revealed 11,000 binding sites with 3,600 of high affinity and 7,400 of low affinity. Removal of the sialic acid of the f.VIII/vWf protein resulted in no significa nt change in its ability to bind to the P surface or cause agglutination in the presence, IR. Removal of the galactose by 6-galactosijase resulted in a 75% reduction of binding of the f.VIII/vWf protein and a 91% decrease in the agglutination of human P. Similar studies with galactose oxidase showed that oxidation of the penultimate galactose residue s results in a decrease in agglutination comparable to that seen with 6-galactosidase treatment. These studies indicate that the CHO moiety of the f.VIII/vWf protein is important in both binding to the P surface as well as causing agglutination of human P.

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