RESUMO
The current climate crisis demands replacement of fossil energy sources with sustainable alternatives. In this scenario, second-generation bioethanol, a product of lignocellulosic biomass fermentation, represents a more sustainable alternative. However, Saccharomyces cerevisiae cannot metabolize pentoses, such as xylose, present as a major component of lignocellulosic biomass. Xylose isomerase (XI) is an enzyme that allows xylose consumption by yeasts, because it converts xylose into xylulose, which is further converted to ethanol by the pentose-phosphate pathway. Only a few XI were successfully expressed in S. cerevisiae strains. This work presents a new bacterial XI, named GR-XI 1, obtained from a Brazilian goat rumen metagenomic library. Phylogenetic analysis confirmed the bacterial origin of the gene, which is related to Firmicutes XIs. After codon optimization, this enzyme, renamed XySC1, was functionally expressed in S. cerevisiae, allowing growth in media with xylose as sole carbon source. Overexpression of XySC1 in S. cerevisiae allowed the recombinant strain to efficiently consume and metabolize xylose under aerobic conditions.
Assuntos
Aldose-Cetose Isomerases , Cabras , Microbiota , Rúmen , Saccharomyces cerevisiae , Aldose-Cetose Isomerases/genética , Aldose-Cetose Isomerases/metabolismo , Animais , Fermentação , Cabras/microbiologia , Filogenia , Rúmen/enzimologia , Rúmen/microbiologia , Saccharomyces cerevisiae/metabolismo , Xilose/metabolismoRESUMO
Isomerases are enzymes that induce physical changes in a molecule without affecting the original molecular formula. Among this class of enzymes, xylose isomerases (XIs) are the most studied to date, partly due to their extensive application in industrial processes to produce high-fructose corn sirups. In recent years, the need for sustainable initiatives has triggered efforts to improve the biobased economy through the use of renewable raw materials. In this context, D-xylose usage is crucial as it is the second-most abundant sugar in nature. The application of XIs in biotransforming xylose, enabling downstream metabolism in several microorganisms, is a smart strategy for ensuring a low-carbon footprint and producing several value-added biochemicals with broad industrial applications such as in the food, cosmetics, pharmaceutical, and polymer industries. Considering recent advancements that have expanded the range of applications of XIs, this review provides a comprehensive and concise overview of XIs, from their primary sources to the biochemical and structural features that influence their mechanisms of action. This comprehensive review may help address the challenges involved in XI applications in different industries and facilitate the exploitation of xylose bioprocesses.
Assuntos
Aldose-Cetose Isomerases , Xilose , Aldose-Cetose Isomerases/química , Aldose-Cetose Isomerases/metabolismo , Saccharomyces cerevisiae/metabolismo , Xilose/metabolismoRESUMO
This study reports an alternative strategy for the expression of a recombinant L-AI from Enterococcus faecium DBFIQ E36 by auto-induction using glucose and glycerol as carbon sources and residual whey lactose as inducer agent. Commercial lactose and isopropyl ß-D-1-thiogalactopyranoside (IPTG) were also evaluated as inducers for comparison of enzyme expression levels. The enzymatic extracts were purified by affinity chromatography, characterized, and applied in the bioconversion of D-galactose into D-tagatose. L-AI presented a catalytic activity of 1.67 ± 0.14, 1.52 ± 0.01, and 0.7 ± 0.04 U/mL, when expressed using commercial lactose, lactose from whey, and IPTG, respectively. Higher activities could be obtained by changing the protocol of enzyme extraction and, for instance, the enzymatic extract produced with whey presented a catalytic activity of 3.8 U/mL. The specific activity of the enzyme extracts produced using lactose (commercial or residual whey) after enzyme purification was also higher when compared to the enzyme expressed with IPTG. Best results were achieved when enzyme expression was conducted using 4 g/L of residual whey lactose for 11 h. These results proved the efficacy of an alternative and economic protocol for the effective expression of a recombinant L-AI aiming its high-scale production.
Assuntos
Aldose-Cetose Isomerases/genética , Aldose-Cetose Isomerases/metabolismo , Enterococcus faecium/enzimologia , Escherichia coli/crescimento & desenvolvimento , Isopropiltiogalactosídeo/metabolismo , Lactose/metabolismo , Aldose-Cetose Isomerases/isolamento & purificação , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Clonagem Molecular , Meios de Cultura/química , Enterococcus faecium/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Regulação Bacteriana da Expressão Gênica , Regulação Enzimológica da Expressão Gênica , Glucose/metabolismo , Glicerol/metabolismo , Concentração de Íons de Hidrogênio , Proteínas Recombinantes/metabolismo , Soro do Leite/químicaRESUMO
Ribose 5-phosphate isomerase type B (RPI-B) is a key enzyme of the pentose phosphate pathway that catalyzes the isomerization of ribose 5-phosphate (R5P) and ribulose 5-phosphate (Ru5P). Trypanosoma cruzi RPI-B (TcRPI-B) appears to be a suitable drug-target mainly due to: (i) its essentiality (as previously shown in other trypanosomatids), (ii) it does not present a homologue in mammalian genomes sequenced thus far, and (iii) it participates in the production of NADPH and nucleotide/nucleic acid synthesis that are critical for parasite cell survival. In this survey, we report on the competitive inhibition of TcRPI-B by a substrate - analogue inhibitor, Compound B (Ki = 5.5 ± 0.1 µM), by the Dixon method. This compound has an iodoacetamide moiety that is susceptible to nucleophilic attack, particularly by the cysteine thiol group. Compound B was conceived to specifically target Cys-69, an important active site residue. By incubating TcRPI-B with Compound B, a trypsin digestion LC-MS/MS analysis revealed the identification of Compound B covalently bound to Cys-69. This inhibitor also exhibited notable in vitro trypanocidal activity against T. cruzi infective life-stages co-cultured in NIH-3T3 murine host cells (IC50 = 17.40 ± 1.055 µM). The study of Compound B served as a proof-of-concept so that next generation inhibitors can potentially be developed with a focus on using a prodrug group in replacement of the iodoacetamide moiety, thus representing an attractive starting point for the future treatment of Chagas' disease.
Assuntos
Aldose-Cetose Isomerases/antagonistas & inibidores , Desenho de Fármacos , Inibidores Enzimáticos/química , Proteínas de Protozoários/antagonistas & inibidores , Tripanossomicidas/síntese química , Trypanosoma cruzi/enzimologia , Células 3T3 , Aldose-Cetose Isomerases/metabolismo , Animais , Sítios de Ligação , Domínio Catalítico , Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/farmacologia , Cinética , Camundongos , Simulação de Dinâmica Molecular , Proteínas de Protozoários/metabolismo , Especificidade por Substrato , Tripanossomicidas/metabolismo , Tripanossomicidas/farmacologia , Trypanosoma cruzi/efeitos dos fármacosRESUMO
Apple (Malus domestica) fruits accumulate negligible levels of carotenoids, antioxidant pigments that are precursors for vitamin A in humans. As vitamin A deficiency is an important public health issue, we aimed at increasing carotenoids in apple by constitutively expressing the Arabidopsis thaliana DXR gene, one of the key regulatory steps in the plastidial isoprenoid pathway. For this purpose, we optimized an Agrobacterium-mediated transformation method in the commercial Fuji Raku Raku variety. This resulted in a shoot establishment efficiency of 0.75% at 20 weeks after infection. Molecular and microscopical analyses revealed that 80% of the hygromycin resistant shoots contained and expressed AtDXR:eGFP and that the AtDXR:eGFP fusion protein located in plastids. Transgenic seedlings displayed up to 3-fold increase in total carotenoids and in individual carotenoids compared to the WT, correlating with an increased transcript abundance of endogenous carotenogenic genes such as MdDXS, MdPSY1, MdPSY2, MdPSY3, MdLCYB1, and MdLCYB2. In addition, buds of 2-year-old transgenic dormant trees showed an increment up to 3-fold in lutein, and transient transformation of fruits revealed that AtDXR induced a 2-fold increment in total carotenoids. Thus, these results suggest that DXR may be a good candidate for increasing carotenoid levels in apple fruits through metabolic engineering.
Assuntos
Agrobacterium/genética , Aldose-Cetose Isomerases/genética , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Carotenoides/metabolismo , Malus/genética , Aldose-Cetose Isomerases/metabolismo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Malus/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Transformação GenéticaRESUMO
BACKGROUND: Enzymatic isomerization is a promising strategy to solve the problem of xylose fermentation and, consequently, to leverage the production of advanced biofuels and biochemicals. In a previous work, our research group discovered a new strain of Streptomyces with great biotechnological potential due to its ability to produce a broad arsenal of enzymes related to lignocellulose degradation. METHODS: We applied a multidisciplinary approach involving enzyme kinetics, biophysical methods, small angle X-ray scattering and X-ray crystallography to investigate two novel xylose isomerases, XylA1F1 and XylA2F1, from this strain. RESULTS: We showed that while XylA1F1 prefers to act at lower temperatures and relatively lower pH, XylA2F1 is extremely stable at higher temperatures and presents a higher turnover number. Structural analysis revealed that XylA1F1 exhibits unique properties in the active site not observed in classical XylAs from classes I and II nor in its ortholog XylA2F1. It encompasses the natural substitutions, M86A and T93K, that create an extra room for substrate accommodation and narrow the active-site entrance, respectively. Such modifications may contribute to the functional differentiation of these enzymes. CONCLUSIONS: We have characterized two novel xylose isomerases that display distinct functional behavior and harbor unprecedented amino-acid substitutions in the catalytic interface. GENERAL SIGNIFICANCE: Our findings contribute to a better understanding of the functional and structural aspects of xylose isomerases, which might be instrumental for the valorization of the hemicellulosic fraction of vegetal biomass.
Assuntos
Aldose-Cetose Isomerases/química , Streptomyces/enzimologia , Aldose-Cetose Isomerases/metabolismo , Sequência de Aminoácidos , Domínio Catalítico , Cristalografia por Raios X , Modelos Moleculares , Conformação Proteica , Alinhamento de Sequência , Streptomyces/química , Streptomyces/metabolismo , Especificidade por SubstratoRESUMO
Understanding the regulatory mechanisms that affect obesogenic genes expression in newborns is essential for early prevention efforts, but they remain unclear. Our study aimed to explore whether the maternal p-BMI and GWG were associated with regulatory single-locus DNA methylation in selected obesogenic genes. For this purpose, DNA methylation was assayed by Methylation-Sensitive High Resolution Melting (MS-HRM) technique and Sanger allele-bisulfite sequencing in fifty samples of umbilical vein to evaluate glucosamine-6-phosphate deaminase 2 (GNPDA2), peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α), and leptin receptor (LEPR) genes. Correlations between DNA methylation levels and indicators of maternal nutritional status were carried out. Western blotting was used to evaluate protein expression in extracts of the same samples. Results indicated that GNPDA2 and PGC1α genes have the same level of DNA methylation in all samples; however, a differential DNA methylation of LEPR gene promoter was found, correlating it with GWG and this correlation is unaffected by maternal age or unhealthy habits. Furthermore, leptin receptor (Lep-Rb) was upregulated in samples that showed the lowest levels of DNA methylation. This study highlights the association between poor GWG and adjustments on obesogenic genes expression in newborn tissues with potential consequences for development of obesity in the future.
Assuntos
Aldose-Cetose Isomerases/metabolismo , Metilação de DNA , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Receptores para Leptina/metabolismo , Veias Umbilicais/metabolismo , Adolescente , Adulto , Aldose-Cetose Isomerases/genética , Índice de Massa Corporal , Feminino , Ganho de Peso na Gestação , Humanos , Estado Nutricional , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/genética , Gravidez , Primeiro Trimestre da Gravidez , Regiões Promotoras Genéticas , Receptores para Leptina/genética , Adulto JovemRESUMO
D-Tagatose is a ketohexose, which presents unique properties as a low-calorie functional sweetener possessing a sweet flavor profile similar to D-sucrose and having no aftertaste. Considered a generally recognized as safe (GRAS) substance by FAO/WHO, D-tagatose can be used as an intermediate for the synthesis of other optically active compounds as well as an additive in detergent, cosmetic, and pharmaceutical formulations. This study reports important features for L-arabinose isomerase (EC 5.3.1.4) (L-AI) use in industry. We describe arabinose (araA) gene virulence analysis, gene isolation, sequencing, cloning, and heterologous overexpression of L-AI from the food-grade GRAS bacterium Enterococcus faecium DBFIQ E36 in Escherichia coli and assess biochemical properties of this recombinant enzyme. Recombinant L-AI (rL-AI) was one-step purified to homogeneity by Ni2+-agarose resin affinity chromatography and biochemical characterization revealed low identity with both thermophilic and mesophilic L-AIs but high degree of conservation in residues involved in substrate recognition. Optimal conditions for rL-AI activity were 50 °C, pH 5.5, and 0.3 mM Mn2+, exhibiting a low cofactor concentration requirement and an acidic optimum pH. Half-life at 45 °C and 50 °C were 1427 h and 11 h, respectively, and 21.5 h and 39.5 h at pH 4.5 and 5.6, respectively, showing the high stability of the enzyme in the presence of a metallic cofactor. Bioconversion yield for D-tagatose biosynthesis was 45% at 50 °C after 48 h. These properties highlight the technological potential of E. faecium rL-AI as biocatalyst for D-tagatose production.
Assuntos
Aldose-Cetose Isomerases/metabolismo , Proteínas de Bactérias/metabolismo , Enterococcus faecium/enzimologia , Galactose/metabolismo , Hexoses/biossíntese , Aldose-Cetose Isomerases/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Cátions Bivalentes , Clonagem Molecular , Coenzimas/metabolismo , Enterococcus faecium/genética , Ensaios Enzimáticos , Estabilidade Enzimática , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Temperatura Alta , Concentração de Íons de Hidrogênio , Cinética , Manganês/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade por SubstratoRESUMO
A recombinant L-arabinose isomerase from Enterococcus faecium DBFIQ E36 was immobilized onto multifunctional epoxide supports by chemical adsorption and onto a chelate-activated support via polyhistidine-tag, located on the N-terminal (N-His-L-AI) or on the C-terminal (C-His-L-AI) sequence, followed by covalent bonding between the enzyme and the support. The results were compared to reversible L-AI immobilization by adsorption onto charged agarose supports with improved stability. All the derivatives presented immobilization yields of above 75%. The ionic interaction established between agarose gels containing monoaminoethyl-N-aminoethyl structures (MANAE) and the enzyme was the most suitable strategy for L-AI immobilization in comparison to the chelate-activated agarose. In addition, the immobilized biocatalysts by ionic interaction in MANAE showed to be the most stable, retaining up to 100% of enzyme activity for 60 min at 60 °C and with Km values of 28 and 218 mM for MANAE-N-His-L-AI and MANAE-C-His-L-AI, respectively.
Assuntos
Aldose-Cetose Isomerases/metabolismo , Proteínas de Bactérias/metabolismo , Enterococcus faecium/enzimologia , Hexoses/biossíntese , Aldose-Cetose Isomerases/genética , Proteínas de Bactérias/genética , Biocatálise , Biotecnologia , Enterococcus faecium/genética , Estabilidade Enzimática , Enzimas Imobilizadas/genética , Enzimas Imobilizadas/metabolismo , Temperatura Alta , Concentração de Íons de Hidrogênio , Cinética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , SolubilidadeRESUMO
Despite the versatility and many advantages of polyhydroxyalkanoates as petroleum-based plastic substitutes, their higher production cost compared to petroleum-based polymers has historically limited their large-scale production. One appealing approach to reducing production costs is to employ less expensive, renewable feedstocks. Xylose, for example is an abundant and inexpensive carbon source derived from hemicellulosic residues abundant in agro-industrial waste (sugarcane bagasse hemicellulosic hydrolysates). In this work, the production of poly-3-hydroxybutyrate P(3HB) from xylose was studied to develop technologies for conversion of agro-industrial waste into high-value chemicals and biopolymers. Specifically, this work elucidates the organization of the xylose assimilation operon of Burkholderia sacchari, a non-model bacterium with high capacity for P(3HB) accumulation. Overexpression of endogenous xylose isomerase and xylulokinase genes was successfully assessed, improving both specific growth rate and P(3HB) production. Compared to control strain (harboring pBBR1MCS-2), xylose utilization in the engineered strain was substantially improved with 25% increase in specific growth rate, 34% increase in P(3HB) production, and the highest P(3HB) yield from xylose reported to date for B. sacchari (YP3HB/Xil = 0.35 g/g). This study highlights that xylA and xylB overexpression is an effective strategy to improve xylose utilization and P(3HB) production in B. sacchari.