RESUMEN
Arginase catalyzes the first committed step in the biosynthesis of polyamines that enable cell growth and hence potential drug target for the treatment of leishmaniasis. The arginase from Leishmania donovani (LdARG) was cloned, overexpressed and characterized. Analysis of the deduced amino acid sequence of LdARG with homologous enzyme from other trypanosomatids arginases identified a non-conserved 12 residues long segment VWGLIERTFLSA from position 161-172. This counter segment in L. mexicana arginase exhibits a different conformation compared with human arginase I. The pH and temperature optima of LdARG were 9.0 and 37⯰C, respectively. Biochemical studies revealed that the KM for the substrate L-arginine was 24.76⯱â¯0.06â¯mM. Molecular modeling of LdARG studies revealed that the glutamic acid residue at position 288 plays a role in substrate binding. The importance of this glutamic acid residue was validated by constructing a mutant variant of LdARG (E288Q-LdARG) by replacing glutamic acid with glutamine through site-directed mutagenesis. The KM value of mutant variant for L-arginine was found to be 107⯱â¯0.18â¯mM. The increase in KM value of E288Q-LdARG as compared to LdARG suggested that substrate binding was significantly affected which could be exploited further. Studies on biochemical and structural characterization of recombinant LdARG will help in evaluating this enzyme as a potential drug target for visceral leishmaniasis.
Asunto(s)
Arginasa/metabolismo , Leishmania donovani/metabolismo , Poliaminas/química , Proteínas Protozoarias/metabolismo , Proteínas Recombinantes/metabolismo , Secuencia de Aminoácidos , Arginasa/genética , Sitios de Unión , Biocatálisis , Inhibidores Enzimáticos/metabolismo , Ácido Glutámico/química , Glutamina/química , Cinética , Simulación de Dinámica Molecular , Mutagénesis Sitio-Dirigida , Mutación , Unión Proteica , Conformación Proteica , Proteínas Protozoarias/genética , Proteínas Recombinantes/genética , TermodinámicaRESUMEN
Phosphoglycerate kinase (PGK) is a glycolytic enzyme present in many parasites. It has been reported as a candidate molecule for drug and vaccine developments. In the present study, a full-length cDNA encoding the Brugia malayi 3-phosphoglycerate kinase (BmPGK) with an open reading frame of 1.3 kb was isolated and PCR amplified and cloned. The exact size of the BmPGK's ORF is 1377 bps. The BmPGK gene was subcloned into pET-28a (+) expression vector, the expressed enzyme was purified by affinity column and characterized. The SDS-PAGE analysis revealed native molecular weight of recombinant Brugia malayi 3-phosphoglycerate kinase (rBmPGK) to be â¼45 kDa. The enzyme was found sensitive to temperature and pH, it showed maximum activity at 25 °C and pH 8.5. The Km values for PGA and ATP were 1.77 and 0.967 mM, respectively. The PGK inhibitor, clorsulon and antifilarial drugs albendazole and ivermectin inhibited the enzyme. The specific inhibitor of PGK, clorsulon, competitively inhibited enzyme with Ki value 1.88 µM. Albendazole also inhibited PGK competitively with Ki value 35.39 µM. Further these inhibitory studies were confirmed by docking and molecular simulation of drugs with enzyme. Clorsulon interacted with substrate binding site with glutamine 37 as well as in hinge regions with aspartic acid 385 and valine 387 at ADP binding site. On the other hand albendazole interacted with asparagine 335 residues. These effects were in good association with binding interactions. Thus current study might help in designing and synthesis of effective inhibitors for this novel drug target and understanding their mode of interaction with the potent anthelmintic drugs.
Asunto(s)
Brugia Malayi , Clonación Molecular , Expresión Génica , Proteínas del Helminto , Sistemas de Lectura Abierta , Fosfoglicerato Quinasa , Animales , Brugia Malayi/enzimología , Brugia Malayi/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas del Helminto/biosíntesis , Proteínas del Helminto/química , Proteínas del Helminto/genética , Proteínas del Helminto/aislamiento & purificación , Fosfoglicerato Quinasa/biosíntesis , Fosfoglicerato Quinasa/química , Fosfoglicerato Quinasa/genética , Fosfoglicerato Quinasa/aislamiento & purificación , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/aislamiento & purificaciónRESUMEN
Serine hydroxymethyltransferase belongs to the class of pyridoxal-5-phosphate enzymes along with aspartate aminotransferase. To explore the function of residue(s) involved in binding of the carboxylate group of Tetrahydrofolic acid (THF) to L. donovani cytosolic serine hydroxymethyltransferase (LdcSHMT), the gene was cloned in pET-28(a) vector, overexpressed and purified to homogeneity. With the help of docking results of THF to the active site of protein, the key residues involved in interaction were identified. In an attempt to unravel the function of Arg265 residue involved in binding of the carboxylate group of THF, Arg-265 was mutated to Ala by site-directed mutagenesis. The Arg265Ala-LdcSHMT showed increased Km value (threefold) and decreased kcat/Km value (threefold) for H4-folate as compared with wild type enzyme. The wild and mutant enzymes exhibited similar Km and kcat/Km values for L-allo-threonine. Unlike the wild type enzyme, mutant failed to form characteristic quinonoid intermediate and was unable to carry out the exchange of α-proton from glycine in the presence of Tetrahydrofolate. These results suggested that Arg265 residue is required for the binding of Tetrahydrofolate and may be the base that abstracts α-proton from glycine, leading to formation of quinonoid intermediate in cytosolic SHMT of L. donovani.
Asunto(s)
Arginina/fisiología , Glicina Hidroximetiltransferasa/metabolismo , Leishmania donovani/metabolismo , Tetrahidrofolatos/metabolismo , Alanina/química , Alanina/genética , Secuencia de Aminoácidos , Arginina/química , Arginina/genética , Clonación Molecular , Citosol/enzimología , ADN Protozoario/química , Escherichia coli/genética , Vectores Genéticos , Glicina Hidroximetiltransferasa/química , Glicina Hidroximetiltransferasa/genética , Leishmania donovani/enzimología , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Plásmidos , Estructura Secundaria de Proteína , Análisis Espectral , Tetrahidrofolatos/químicaRESUMEN
The antidyslipidemic activity of Ocimum sanctum leaf extract was studied in streptozotocin induced diabetic rats. In this model, there was significant increase in plasma markers of diabetic-dyslipidemia following diminution of lipid metabolizing enzymes. Oral administration of leaf extract (500 mg/kg b.w.p.o.) for 15 days resulted in significant decrease in diabetogenic and dyslipidemia parameters; namely blood glucose, glycosylated hemoglobin, lipid peroxide, free fatty acids, small dense low density lipoprotein, lipid and protein components of plasma lipoproteins, adipose and liver. The regulation of lipids was accompanied by stimulation of postheparin lipolytic activity, reactivation of lecithin cholesterol acyl transferase and hepatic lipoprotein lipase enzymes. The results of the present study demonstrated antidyslipidemic and antioxidant activities in leaf extract of O. sanctum which could be used in prevention of diabetic-dyslipidemia and related complications.
RESUMEN
The hypolipidemic activity of Cassia tora (Chakvat, Chakunda) (Family: Caesalpiniaceae) seeds extract have been studied in two models of hyperlipidemia in rats. In an acute model, hyperlipidemia was induced by injecting a single dose of Triton WR-1339 (400 mg/kg, b.w.) intraperitonially in rats. Feeding with C. tora seed extract at the dose of 500 mg/kg, b.w. exerted significant lipid lowering effect as assessed by the reversal of plasma levels of total cholesterol, phospholipids, triglyceride and reactivation of post heparin lipolytic activity. In the chronic model, hyperlipidemia was induced by feeding with cholesterol rich-HFD in rats. The treatment with seeds extract of C. tora (500 mg/kg, b.w.) simultaneously for 15 days also caused lowering of lipid levels in plasma and liver following reactivation of plasma post heparin lipolytic activity and hepatic lipoprotein lipase activity in animals. The hypolipidemic activity of C. tora seeds was compared with a standard drug guggulipid (200 mg/kg, b.w.) in both models.
RESUMEN
The antidyslipidemic activity of Hibiscus rosa sinensis (Malvaceae) root extract has been studied in alloxan induced diabetic rats. In this model, oral administration of root extract (500 mg/kg bw. p.o.) for 15 days resulted in significant decreased in the levels of blood glucose, plasma lipids and reactivated post heparin lipoprotein lipase activity in alloxan induced diabetic rats. Furthermore, the root extract (50-500 µg) when tested for its antioxidant activity, inhibited the generation of super oxide anions and hydroxyl radicals, in both enzymic and non enzymic systems in vitro. The results of the present study demonstrated antidyslipidemic and antioxidant activities in root extract of H. rosa sinensis which could be used in prevention of diabetic-dyslipidemia and related complications.
RESUMEN
BACKGROUND: As per estimates by WHO in 2021 almost half of the world's population was at risk of malaria and > 0.6 million deaths were attributed to malaria. Therefore, the present study was aimed to explore the antimalarial activity of extracts derived from the leaves of the plant Anacardium occidentale L., which has been used traditionally for the treatment of malaria. Different extracts of A. occidentale leaves were prepared and tested for their inhibitory activity against recombinant P. falciparum transketolase (rPfTK) enzyme, in vitro. Further, growth inhibitory activity against cultivated blood stage P. falciparum parasites (3D7 strain), was studied using SYBR Green fluorescence-based in vitro assays. Acute toxicity of the hydro alcoholic extracts of leaves of A. occidentale (HELA) at different concentrations was evaluated on mice and Zebra fish embryos. HELA showed 75.45 ± 0.35% inhibitory activity against the recombinant PfTk and 99.31 ± 0.08% growth inhibition against intra-erythrocytic stages of P. falciparum at the maximum concentration (50 µg/ml) with IC50 of 4.17 ± 0.22 µg/ml. The toxicity test results showed that the heartbeat, somite formation, tail detachment and hatching of embryos were not affected when Zebra fish embryos were treated with 0.1 to 10 µg/ml of the extract. However, at higher concentrations of the extract, at 48 h (1000 µg/ml) and 96 h (100 µg/ml and 1000 µg/ml, respectively) there was no heartbeat in the fish embryos. In the acute oral toxicity tests performed on mice, the extract showed no toxicity up to 300 mg/kg body weight in mice. CONCLUSION: The hydro-alcoholic extract of leaves of A. occidentale L. showed potent antimalarial activity against blood stage P. falciparum. Based on the observed inhibitory activity on the transketolase enzyme of P. falciparum it is likely that this enzyme is the target for the development of bioactive molecules present in the plant extracts. The promising anti-malarial activity of purified compounds from leaves of A. occidentale needs to be further explored for development of new anti-malarial therapy.
Asunto(s)
Anacardium , Antimaláricos , Malaria Falciparum , Malaria , Animales , Ratones , Antimaláricos/toxicidad , Plasmodium falciparum , Transcetolasa/uso terapéutico , Pez Cebra , Malaria/tratamiento farmacológico , Malaria/parasitología , Malaria Falciparum/tratamiento farmacológico , Extractos Vegetales/farmacologíaRESUMEN
PURPOSE: We identified calreticulin in human filaria Brugia malayi (BmCRT) that shares 97% homology with Wuchereria bancrofti calreticulin (WbCRT), but only 56% with human calreticulin. We found that BmCRT binds C1q and prevents complement-mediated parasite death; immunization with BmCRT leads to parasite death in a rodent model of the infection. BmCRT could, therefore, be a potential vaccine candidate. In the present study, we determined the levels of BmCRT-reactive IgG and its isotype in bancroftian filarial subjects. METHODS: Recombinant BmCRT (rBmCRT) was prepared, and the sera of endemic normal subjects (EN), microfilaraemics (Mf+) and chronic amicrofilaraemics (ChMf-) from a bancroftian filaria-endemic area and normal subjects from filaria-non-endemic area (NEN) were probed for IgG and its isotypes reacting with rBmCRT and its domains rN, rP and rC. RESULTS: rBmCRT and its rN domain-reactive IgG levels were high in EN and Mf+ groups; rC domain and rP domain showed moderate and very little reactivity, respectively. NEN sera were non-reactive. Moderate levels of rBmCRT-reactive IgG1, IgG3 and IgG4 in EN and Mf+ groups and low levels of IgG2 in Mf+ were found; IgG1 and IgG3 reactivity was found for rBmCRT and its rN domain only, while IgG4 reactivity was moderate for rN domain and low for rP and rC domains. While IgG reactivity was seen in all the endemic subjects, IgG isotype reactivity was found mostly in EN and Mf+ subjects. CONCLUSIONS: Moderate levels of rBmCRT (and its rN domain)-reactive IgG and its isotypes are present in bancroftian subjects. Preponderance of IgG1 and IgG3 isotypes which bind and activate complement has relevance to vaccine potential of BmCRT.
Asunto(s)
Brugia Malayi , Filariasis Linfática , Vacunas , Animales , Anticuerpos Antihelmínticos , Antígenos Helmínticos , Calreticulina/metabolismo , Filariasis Linfática/prevención & control , Humanos , Inmunización , Inmunoglobulina GRESUMEN
Plasmodium lacks the de novo pathway for purine biosynthesis and relies exclusively on the salvage pathway. Adenosine deaminase (ADA), first enzyme of the pathway, was purified and characterized from Plasmodium yoelii, a rodent malarial species, using ion exchange and gel exclusion chromatography. The purified enzyme is a 41 kDa monomer. The enzyme showed K(m) values of 41 µM and 34 µM for adenosine and 2'-deoxyadenosine, respectively. Erythro-9-(2-hydroxy-3-nonyl) adenine competitively inhibited P. yoelii ADA with K(i) value of 0.5 µM. The enzyme was inhibited by DEPC and protein denaturing agents, urea and GdmCl. Purine analogues significantly inhibited ADA activity. Inhibition by p-chloromercuribenzoate (pCMB) and N-ethylmaleimide (NEM) indicated the presence of functional -SH groups. Tryptophan fluorescence maxima of ADA shifted from 339 nm to 357 nm in presence of GdmCl. Refolding studies showed that higher GdmCl concentration irreversibly denatured the purified ADA. Fluorescence quenchers (KI and acrylamide) quenched the ADA fluorescence intensity to the varied degree. The observed differences in kinetic properties of P. yoelii ADA as compared to the erythrocyte enzyme may facilitate in designing specific inhibitors against ADA.
Asunto(s)
Adenosina Desaminasa/química , Adenosina Desaminasa/aislamiento & purificación , Plasmodium yoelii/enzimología , Adenosina Desaminasa/inmunología , Adenosina Desaminasa/metabolismo , Inhibidores de la Adenosina Desaminasa/farmacología , Sulfato de Amonio , Animales , Especificidad de Anticuerpos , Antimaláricos/farmacología , Fraccionamiento Químico , Cromatografía en Gel , Cromatografía por Intercambio Iónico , Electroforesis en Gel de Poliacrilamida , Guanidina/farmacología , Concentración de Iones de Hidrógeno , Cinética , Ratones , Peso Molecular , Purinas/farmacología , Conejos , Espectrometría de FluorescenciaRESUMEN
Lymphatic filariasis causes permanent and long-term disability worldwide. Lack of potent adulticidal drugs, the emergence of drug resistance, and the nonavailability of effective vaccines are the major drawbacks toward LF elimination. However, immunomodulatory proteins present in the parasite secretome are capable of providing good protection against LF and thus offer hope in designing new vaccines against LF. Here, we evaluated the immunogenicity and protective efficacy of B. malayi calreticulin protein (BmCRT) using in vitro and in vivo approaches. Stimulation with recombinant BmCRT (rBmCRT) significantly upregulated Th1 cytokine production in mouse splenocytes, mesenteric lymph nodes (mLNs), and splenic and peritoneal macrophages (PMΦs). Heightened NO release, ROS generation, increased lymphocyte proliferation, and increased antigen uptake were also observed after rBmCRT exposure. Mice immunized with rBmCRT responded with increased Th1 and Th2 cytokine secretion and exhibited highly elevated titers of anti-BmCRT specific IgG at day 14 and day 28 postimmunization while splenocytes and mLNs from immunized mice showed a robust recall response on restimulation with rBmCRT. Infective larvae (L3) challenge and protection studies undertaken in Mastomys coucha, a permissive model for LF, showed that rBmCRT-immunized animals mounted a robust humoral immune response as evident by elevated levels of total IgG, IgG1, IgG2a, IgG2b, and IgG3 in their serum even 150 days after L3 challenge, which led to significantly reduced microfilariae and worm burden in infected animals. BmCRT is highly immunogenic and generates robust antiparasitic immunity in immunized animals and should therefore be explored further as a putative vaccine candidate against LF.
Asunto(s)
Brugia Malayi , Filariasis Linfática , Animales , Antiparasitarios , Brugia Malayi/metabolismo , Calreticulina/genética , Citocinas/metabolismo , Filariasis Linfática/prevención & control , Inmunización , RatonesRESUMEN
Guanidine hydrochloride and urea-induced unfolding of B. malayi hexokinase (BmHk), a tetrameric protein, was examined in detail by using various optical spectroscopic techniques, enzymatic activity measurements, and size-exclusion chromatography. The equilibrium unfolding of BmHk by guanidine hydrochloride (GdmCl) and urea proceeded through stabilization of several unique oligomeric intermediates. In the presence of low concentrations of GdmCl, stabilization of an enzymatically active folded dimer of BmHk was observed. However an enzymatically inactive dimer of BmHk was observed for urea-treated BmHk. This is the first report of an enzymatically active dimer of hexokinase from any human filarial parasite. Furthermore, although complete recovery of the native enzyme was observed on refolding of BmHk samples denatured by use of low concentrations of GdmCl or urea, no recovery of the native enzyme was observed for BmHk samples denatured by use of high concentrations of GdmCl or urea.
Asunto(s)
Brugia Malayi/química , Brugia Malayi/enzimología , Guanidina/química , Proteínas del Helminto/química , Hexoquinasa/química , Urea/química , Animales , Cromatografía en Gel , Dicroismo Circular , Glutaral/química , Cinética , Conformación Proteica , Desnaturalización Proteica , Pliegue de Proteína , Multimerización de Proteína , Espectrometría de FluorescenciaRESUMEN
The lipid lowering activity of Anthocephalus indicus (family Rubiaceae; Hindi name Kadamba) root extract has been studied in triton WR-1339 induced hyperlipidemia in rats. In this model, feeding with root extract (500 mg kg(-1) b.w.) lowered plasma lipids and reactivated post-heparin lipolytic activity in hyperlipidemic rats. Furthermore, the root extract (50-500 µM) inhibited the generation of superoxide anions and hydroxyl radicals, in both enzymic and non-enzymic systems, in vitro. The results of the present study demonstrated both lipid lowering and antioxidant activities in root extract of A. indicus, which could help prevention of hyperlipidemia and related diseases.
RESUMEN
The present study was carried out to explore the anti-diabetic, anti-dyslipoproteinemic and anti-oxidant activities of Anthocephalus indicus root extract in alloxan-induced (150 mg/kg body wt.) diabetic rats. A marked increase in plasma levels of glucose and lipid peroxides accompanied with an elevation in the lipids and apoprotein levels of serum very low density lipoprotein (VLDL) and low density lipoprotein (LDL) following decrease in lipid and protein constituents of high density lipoprotein (HDL) were observed. The alterations in lipoprotein pattern was associated with inhibition of lipolytic and antioxidant enzymes. Oral administration of root extract (500 mg/kg body wt.) for 30 days in dyslipidemic animals resulted in significant decrease in plasma glucose, total cholesterol, phospholipids, triglyceride and lipid peroxides. The decrease of lipids and apoprotein levels of VLDL and LDL were followed by stimulation of plasma post-heparin lipolytic activity and lecithin cholesterol acyltransferase as well as hepatic superoxide dismutase and catalase activities. Lipid and apoprotein levels of HDL were also recovered partially on treatment with root extract.
Asunto(s)
Antioxidantes/farmacología , Hipolipemiantes/farmacología , Extractos Vegetales/farmacología , Raíces de Plantas/química , Árboles/química , Animales , Antioxidantes/uso terapéutico , Ácidos y Sales Biliares/metabolismo , Diabetes Mellitus Experimental/sangre , Diabetes Mellitus Experimental/tratamiento farmacológico , Diabetes Mellitus Experimental/metabolismo , Ácidos Grasos/sangre , Ácidos Grasos/metabolismo , Heces , Hipolipemiantes/uso terapéutico , Metabolismo de los Lípidos/efectos de los fármacos , Peróxidos Lipídicos/sangre , Hígado/efectos de los fármacos , Hígado/enzimología , Hígado/metabolismo , Masculino , RatasRESUMEN
The hypolipidemic activity of Hibiscus rosa sinensis (family Malvaceae) root extract was studied on triton and cholesterol-rich high fat diet (HFD) induced models of hyperlipidemia in rats. In triton WR-1339-induced hyperlipidemia, feeding with root extract (500 mg/kg body wt/day p.o.) exerted lipid-lowering effect, as assessed by reversal of plasma levels of total cholesterol (TC), phospholipids (PL) and triglycerides (TG) and reactivation of post-heparin lipolytic activity (PHLA) of plasma. The other model was fed with cholesterol-rich HFD and root extract (500 mg/kg body wt/ day p.o.) simultaneously for 30 days. This also caused lowering of lipid levels in plasma and liver homogenate and reactivation of plasma PHLA and hepatic total lipoprotein lipase activity. The hypolipidemic activity of Hibiscus rosa sinensis root was compared with a standard drug guggulipid (200 mg/kg body wt/day p.o.), a known lipid- lowering agent in both models. Histopathological findings in rat liver supported the protective role of H. rosa sinensis root extract in preventing cholesterol-rich HFD-induced hepatic steatosis.
Asunto(s)
Hibiscus/química , Hipolipemiantes/farmacología , Extractos Vegetales/farmacología , Raíces de Plantas/química , Animales , Colesterol/metabolismo , Grasas de la Dieta/efectos adversos , Hiperlipidemias/inducido químicamente , Hiperlipidemias/metabolismo , Hiperlipidemias/patología , Hígado/efectos de los fármacos , Hígado/patología , Masculino , Fitoterapia , Polietilenglicoles/farmacología , RatasRESUMEN
The pentose phosphate pathway (PPP) is an important metabolic pathway for yielding reducing power in the form of NADPH and production of pentose sugar needed for nucleic acid synthesis. Transketolase, the key enzyme of non-oxidative arm of PPP, plays a vital role in the survival/replication of the malarial parasite. This enzyme in Plasmodium falciparum is a novel drug target as it has least homology with the human host. In the present study, the P. falciparum transketolase (PfTk) was expressed, localized and biochemically characterized. The recombinant PfTk harboring transketolase activity catalyzed the oxidation of donor substrates, fructose-6-phosphate (F6P) and hydroxypyruvate (HP), with K(m)(app) values of 2.25 and 4.78 mM, respectively. p-Hydroxyphenylpyruvate (HPP) was a potent inhibitor of PfTk, when hydroxypyruvate was used as a substrate, exhibiting a K(i) value of 305 microM. At the same time, noncompetitive inhibition was observed with F6P. The native PfTk is a hexamer with subunit molecular weight of 70kDa, which on treatment with low concentrations of guanidine hydrochloride (GdmCl) dissociated into functionally active dimers. This protein was localized in the cytosol and nucleus of the parasite as studied by confocal microscopy. A model structure of PfTk was constructed based on the crystal structure of the transketolases of Saccharomyces cerevisae, Leishmania mexicana and Escherichia coli to assess the structural homology. Consistent with the homology modeling predictions, CD analysis indicated that PfTk is composed of 39% alpha-helices and 26% beta-sheets. The availability of a structural model of PfTk and the observed differences in its kinetic properties compared to the host enzyme may facilitate designing of novel inhibitors of PfTk with potential anti-malarial activity.
Asunto(s)
Clonación Molecular , Plasmodium falciparum/enzimología , Transcetolasa/aislamiento & purificación , Transcetolasa/metabolismo , Secuencia de Aminoácidos , Animales , Western Blotting , Núcleo Celular/química , Dicroismo Circular , Citoplasma/química , ADN Protozoario/aislamiento & purificación , Fructosafosfatos/metabolismo , Cinética , Microscopía Confocal , Modelos Moleculares , Datos de Secuencia Molecular , Plasmodium falciparum/citología , Estructura Secundaria de Proteína , Piruvatos/metabolismo , Proteínas Recombinantes/análisis , Proteínas Recombinantes/aislamiento & purificaciónRESUMEN
5' EST from filarial gene database has been subjected to 3' rapid amplification of cDNA ends (RACE), semi-nested PCR and PCR to obtain full-length cDNA of Brugia malayi. Full-length hexokinase gene was obtained from cDNA using gene specific primers. The elicited PCR product was cloned, sequenced and expressed as an active enzyme in Escherichia coli. Sequence analysis of B. malayi hexokinase (BmHk) revealed 59% identity with nematode Caenorhabditis elegans but low similarity with all other available hexokinases including human. BmHk, an apparent tetramer with subunit molecular mass of 72 kDa, was able to phosphorylate glucose, fructose, mannose, maltose and galactose. The Km values for glucose, fructose and ATP were found to be 0.035+/-0.005, 75+/-0.3 and 1.09+/-0.5 mM respectively. BmHk was strongly inhibited by ADP, glucosamine, N-acetyl glucosamine and mannoheptulose. The recombinant enzyme was found to be activated by glucose-6-phosphate. ADP exhibited noncompetitive inhibition with the substrate glucose (Ki=0.55 mM) while, mixed type of inhibition was observed with inorganic pyrophosphate (PPi) when ATP was used as substrate (Ki=9.92 microM). The enzyme activity is highly dependent on maintenance of free sulfhydryl groups. CD analysis indicated that BmHk is composed of 37% alpha-helices and 26% beta-sheets. The observed differences in kinetic properties of BmHk as compared to host enzyme may facilitate designing of specific inhibitors against BmHk.
Asunto(s)
Brugia Malayi/enzimología , Clonación Molecular , Hexoquinasa , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Brugia Malayi/genética , Brugia Malayi/patogenicidad , Dicroismo Circular , Filariasis/parasitología , Proteínas del Helminto/genética , Proteínas del Helminto/metabolismo , Hexoquinasa/química , Hexoquinasa/genética , Hexoquinasa/aislamiento & purificación , Hexoquinasa/metabolismo , Humanos , Masculino , Datos de Secuencia Molecular , Murinae , Análisis de Secuencia de ADNRESUMEN
Calreticulin (CRT), a highly conserved ubiquitous eukaryotic protein with a molecular mass of 46â¯kDa, containing three domains (N, P, and C) is involved in promoting prolonged parasite-host relations. Brugia malayi Calreticulin (BmCRT) is involved in the establishment of parasite infection by suppression of C1q-mediated host immune response. Calcium plays important role in this immunomodulatory mechanism of BmCRT. In the present study binding of calcium with BmCRT region involved in this interaction was investigated and correlated with the accompanying changes in fluorescence, circular dichroism (CD) and UV absorption. The results obtained clearly indicated that BmCRT is a calcium binding protein and contains types two of Ca2+ binding sites, one high affinity Ca2+ binding site at P domain and another low affinity Ca2+ binding site at C domain. Zinc also binds to additional sites that do not have appreciable affinity for the calcium. These studies have provided new knowledge that allows us to describe how the structure of BmCRT responds to interactions with calcium and zinc which is different from human CRT and also discuss how this mechanism help to complex formation with host C1q.
Asunto(s)
Calreticulina/química , Metales/química , Animales , Brugia Malayi/genética , Brugia Malayi/inmunología , Brugia Malayi/metabolismo , Proteínas de Unión al Calcio/química , Proteínas de Unión al Calcio/metabolismo , Calreticulina/genética , Calreticulina/metabolismo , Proteínas Portadoras , Dicroismo Circular , Proteínas del Helminto/química , Proteínas del Helminto/metabolismo , Humanos , Inmunomodulación , Metales/metabolismo , Conformación Molecular , Unión Proteica , Estabilidad Proteica , Desplegamiento Proteico , Relación Estructura-ActividadRESUMEN
Calreticulin of Brugia malayi (BmCRT) play very important role in host-parasite interaction. In previous study it was found that BmCRT is responsible for prevention of host classical complement pathway activation via its interaction with first component C1q of the human host. Therefore, BmCRT is an essential protein for parasite survival and an important drug target to fend filariasis. In the present study, we have carried out a systamatic biophysical characterization of BmCRT protein. Unfolding of BmCRT was found to be non-cooperative two-state process in the presence of both denaturant GdmCl and urea. The results also illustrated that protein lost its 50% activity at 1.5M GdmCl and 3M Urea. Partially unfolded and molten-globule like intermediate state was observed at 0.8 to 1.2M GdmCl while Urea unfolding showed intermediate state at 1.2 to 1.6M. Unfolding pathway monitored with the help of apolar quencher, favor above observations. All of these findings support the presence of detectable intermediate state during unfolding pathway of BmCRT. Furthermore, this study indicates that BmCRT is more stable toward temperature (Tm=65°C), pH and trypsin digestion. These differences in properties as compared to host can be fruitfully utilized for synthesis of compounds effective against the parasite.
Asunto(s)
Brugia Malayi , Calreticulina/química , Proteínas del Helminto/química , Desplegamiento Proteico , Temperatura , Animales , Dicroismo Circular , Concentración de Iones de Hidrógeno , Espectrometría de FluorescenciaRESUMEN
Lymphatic filariasis results in an altered lymphatic system and the abnormal enlargement of body parts, causing pain, serious disability and social stigma. Effective vaccines are still not available nowadays, drugs against the disease is required. Protein disulfide isomerase (PDI) is an essential catalyst of the endoplasmic reticulum which is involved in folding and chaperone activities in different biological systems. Here, we report the enzymatic characterization of a Brugia malayi Protein disulfide isomerase (BmPDI), which was expressed and purified from Escherichia coli BL21 (DE3). Western blotting analysis showed the recombinant BmPDI could be recognized by anti-BmPDI Rabbit serum. The rBmPDI exhibited an optimum activity at pH 8 and 40 °C. The enzyme was inhibited by aurin and PDI inhibitor. Recombinant BmPDI showed interaction with recombinant Brugia malayi calreticulin (rBmCRT). The three-dimensional model for BmPDI and BmCRT was generated by homology modelling. A total of 25 hydrogen bonds were found to be formed between two interfaces. There are 259 non-bonded contacts present in the BmPDI-BmCRT complex and 12 salt bridges were formed in the interaction.
RESUMEN
Lymphatic filariasis is a debilitating disease caused by lymph dwelling nematodal parasites like Wuchereria bancrofti, Brugia malayi and Brugia timori. Thymidylate kinase of B. malayi is a key enzyme in the de novo and salvage pathways for thymidine 5'-triphosphate (dTTP) synthesis. Therefore, B. malayi thymidylate kinase (BmTMK) is an essential enzyme for DNA biosynthesis and an important drug target to rein in filariasis. In the present study, the structural and functional changes associated with recombinant BmTMK, in the presence of protein denaturant GdnHCl, urea and pH were studied. GdnHCl and urea induced unfolding of BmTMK is non-cooperative and influence the functional property of the enzyme much lower than their Cm values. The study delineate that BmTMK is more prone to ionic perturbation. The dimeric assembly of BmTMK is an absolute requirement for enzymatic acitivity and any subtle change in dimeric conformation due to denaturation leads to loss of enzymatic activity. The pH induced changes on structure and activity suggests that selective modification of active site microenvironment pertains to difference in activity profile. This study also envisages that chemical moieties which acts by modulating oligomeric assembly, could be used for better designing of inhibitors against BmTMK enzyme.