RESUMO
XanA is an FeII- and α-ketoglutarate-dependent enzyme responsible for the conversion of xanthine to uric acid. It is unique to fungi and it was first described in Aspergillus nidulans. In this work, we present the preliminary characterization of the XanA enzyme from Aspergillus oryzae, a relevant fungus in food production in Japan. The XanA protein (GenBank BAE56701.1) was expressed as a recombinant protein in Escherichia coli BL21 (DE3) Arctic cells. Initial purification assays showed low protein solubility; therefore, the buffer composition was optimized using a fluorescence-based thermal shift assay. The protein was stabilized in solution in the presence of either 600 µM xanthine, 1 M NaCl, 600 µM α-ketoglutarate or 20% glycerol, which increases the melting temperature (Tm) by 2, 4, 5 and 6 °C respectively. The XanA protein was purified by following a three-step purification protocol. The nickel affinity purified protein was subjected to ion-exchange chromatography once the N-terminal 6XHis-tag had been successfully removed, followed by size-exclusion purification. Dynamic light scattering experiments showed that the purified protein was monodisperse and behaved as a monomer in solution. Preliminary activity assays in the presence of xanthine, α-ketoglutarate, and iron suggest that the enzyme is an iron- and α-ketoglutarate-dependent xanthine dioxygenase. Furthermore, the enzyme's optimum activity conditions were determined to be 25 °C, pH of 7.2, HEPES buffer, and 1% of glycerol. In conclusion, we established the conditions to purify the XanA enzyme from A. oryzae in its active form from E. coli bacteria and determined the optimal activity conditions.
Assuntos
Aspergillus oryzae , Dioxigenases , Proteínas Fúngicas , Aspergillus oryzae/enzimologia , Aspergillus oryzae/genética , Dioxigenases/biossíntese , Dioxigenases/química , Dioxigenases/genética , Dioxigenases/isolamento & purificação , Proteínas Fúngicas/biossíntese , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/isolamento & purificação , Ferro/química , Ferro/metabolismo , Ácidos Cetoglutáricos/química , Ácidos Cetoglutáricos/metabolismo , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificaçãoRESUMO
The essential GTPase Gpn1 mediates RNA polymerase II nuclear targeting and controls microtubule dynamics in yeast and human cells by molecular mechanisms still under investigation. Here, we purified human HisGpn1 expressed as a recombinant protein in bacteria E. coli BL-21 (DE3). Affinity purified HisGpn1 eluted from a size exclusion column as a protein dimer, a state conserved after removing the hexa-histidine tail and confirmed by separating HisGpn1 in native gels, and in dynamic light scattering experiments. Human HisGpn1 purity was higher than 95%, molecularly monodisperse and could be concentrated to more than 10 mg/mL without aggregating. Circular dichroism spectra showed that human HisGpn1 was properly folded and displayed a secondary structure rich in alpha helices. HisGpn1 effectively bound GDP and the non-hydrolyzable GTP analogue GMPPCP, and hydrolyzed GTP. We next tested the importance of the C-terminal tail, present in eukaryotic Gpn1 but not in the ancestral archaeal Gpn protein, on HisGpn1 dimer formation. C-terminal deleted human HisGpn1 (HisGpn1ΔC) was also purified as a protein dimer, indicating that the N-terminal GTPase domain contains the interaction surface needed for dimer formation. In contrast to HisGpn1, however, HisGpn1ΔC dimer spontaneously dissociated into monomers. In conclusion, we have developed a method to purify properly folded and functionally active human HisGpn1 from bacteria, and showed that the C-terminal tail, universally conserved in all eukaryotic Gpn1 orthologues, stabilizes the GTPase domain-mediated Gpn1 protein dimer. The availability of recombinant human Gpn1 will open new research avenues to unveil the molecular and pharmacological properties of this essential GTPase.
Assuntos
Proteínas de Ligação ao GTP/química , Proteínas de Ligação ao GTP/isolamento & purificação , Guanosina Trifosfato/química , Multimerização Proteica , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Ligação ao GTP/genética , Humanos , Hidrólise , Domínios Proteicos , Estrutura Quaternária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificaçãoRESUMO
A novel Cu/ZnSOD from Amaranthus hypochondriacus was cloned, expressed, and characterized. Nucleotide sequence analysis showed an open reading frame (ORF) of 456 bp, which was predicted to encode a 15.6-kDa molecular weight protein with a pI of 5.4. Structural analysis showed highly conserved amino acid residues involved in Cu/Zn binding. Recombinant amaranth superoxide dismutase (rAhSOD) displayed more than 50 % of catalytic activity after incubation at 100 °C for 30 min. In silico analysis of Amaranthus hypochondriacus SOD (AhSOD) amino acid sequence for globularity and disorder suggested that this protein is mainly disordered; this was confirmed by circular dichroism, which showed the lack of secondary structure. Intrinsic fluorescence studies showed that rAhSOD undergoes conformational changes in two steps by the presence of Cu/Zn, which indicates the presence of two binding sites displaying different affinities for metals ions. Our results show that AhSOD could be classified as an intrinsically disordered protein (IDP) that is folded when metals are bound and with high thermal stability.
Assuntos
Amaranthus/enzimologia , Proteínas Intrinsicamente Desordenadas/metabolismo , Superóxido Dismutase/metabolismo , Sequência de Aminoácidos , Cromatografia em Gel , Dicroísmo Circular , Estabilidade Enzimática/efeitos dos fármacos , Fluorescência , Peróxido de Hidrogênio/farmacologia , Proteínas Intrinsicamente Desordenadas/química , Cinética , Metais/farmacologia , Modelos Moleculares , Dados de Sequência Molecular , Multimerização Proteica/efeitos dos fármacos , Proteólise/efeitos dos fármacos , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Cloreto de Sódio/farmacologia , Superóxido Dismutase/química , TemperaturaRESUMO
Canary grass is used as traditional food for diabetes and hypertension treatment. The aim of this work is to characterize the biological activity of encrypted peptides released after gastrointestinal digestion of canary seed proteins. Canary peptides showed 43.5% inhibition of dipeptidyl peptidase IV (DPPIV) and 73.5% inhibition of angiotensin-converting enzyme (ACE) activity. An isolated perfused rat heart system was used to evaluate the canary seed vasoactive effect. Nitric oxide (NO), a major vasodilator agent, was evaluated in the venous effluent from isolated perfused rat heart. Canary seed peptides (1 µg/mL) were able to induce the production of NO (12.24 µM) in amounts similar to those induced by captopril (CPT) and bradykinin (BK). These results show that encrypted peptides in canary seed have inhibitory activity against DPPIV and ACE, enzymes that are targets for diabetes and hypertension treatments.
Assuntos
Anti-Hipertensivos/farmacologia , Hipoglicemiantes/farmacologia , Peptídeos/farmacologia , Phalaris/química , Sementes/química , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Animais , Bradicinina , Captopril , Vasos Coronários/efeitos dos fármacos , Digestão , Masculino , Miocárdio/metabolismo , Óxido Nítrico/análise , Óxido Nítrico/biossíntese , Peptídeos/isolamento & purificação , Peptídeos/metabolismo , Peptidil Dipeptidase A/metabolismo , Ratos , Ratos Wistar , Proteínas de Armazenamento de Sementes/química , Proteínas de Armazenamento de Sementes/isolamento & purificação , Proteínas de Armazenamento de Sementes/metabolismo , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologiaRESUMO
Bioactive compounds present in foods could potentially have beneficial effects on human health. In this study we report the in vitro inhibitory capacity of peptides released from amaranth seed proteins after enzymatic digestion, against dipeptidyl peptidase IV (DPPIV); an enzyme known to deactivate incretins, hormones involved in insulin secretion. Other seeds, such as soybean, black bean, and wheat were also tested. The highest inhibition of DPPIV was observed with amaranth peptides released after simulated gastrointestinal digestion, showing an IC(50) of 1.1mg/mL in a dose-dependent manner. In silico tryptic digestion of amaranth globulins was carried out releasing peptides larger than 13 residues. Some of these peptides were used for the in silico prediction of their binding modes with DPPIV. Docking models showed that the possible mechanism of globulin peptides to inhibit DPPIV was through blocking the active dimer formation. Peptides were also found inside the major cavity where the natural substrates reach the catalytic site of the enzyme. This is the first report of the identification of inhibitory DPPIV peptides from amaranth hydrolysates and the prediction of their binding modes at the molecular level, leading to their possible use as functional food ingredients in the prevention of diabetes.
Assuntos
Amaranthus/química , Inibidores da Dipeptidil Peptidase IV/química , Peptídeos/química , Proteínas de Plantas/química , Amaranthus/genética , Sequência de Aminoácidos , Animais , Domínio Catalítico , Digestão , Dipeptidil Peptidase 4/química , Inibidores da Dipeptidil Peptidase IV/isolamento & purificação , Humanos , Hidrólise , Modelos Biológicos , Dados de Sequência Molecular , Peptídeos/genética , Peptídeos/isolamento & purificação , Proteínas de Plantas/genética , Sementes/química , SuínosRESUMO
Amino acid replacements in the active site of glucosamine-6-P deaminase from Escherichia coli (GlcN6P deaminase, EC 3.5.99.6) involving the residues D141 and E148 produce atypical allosteric kinetics. These residues are located in the chain segment 139-156 which is part of the active site and which also forms several intersubunit contacts close to the allosteric site. In the D141N and E148Q mutant forms of this deaminase, there is an inversion of the effect of its physiological allosteric effector, N-acetylglucosamine 6-P, which becomes an inhibitor at substrate concentrations above a critical value. For both mutants, this particular point appears at low substrate concentration and the inhibition by the allosteric activator is the dominant effect in velocity versus substrate curves. These effects are analyzed as a particular case of the concerted allosteric model, assuming that the R state, the conformer displaying the higher affinity for the substrate, is the less catalytic state, thus producing an inverted allosteric response.