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1.
J Plant Physiol ; 265: 153493, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34403886

RESUMO

As members of the pathogenesis-related protein (PR)-2 family, ß-1,3-glucanases play pivotal roles in plant defense. Previous study showed that the rice genome contains 16 genes encoding putative ß-1,3-glucanases, and the ß-1,3-glucanases in subfamily A were deduced to be involved in plant defense. However, there was limited direct evidence. In this study, the expression of rice ß-1,3-glucanases Gns2-Gns6 belonging to subfamily A in rice plant infection with Magnaporthe oryzae was investigated, and the enhanced expression of Gns6 during infection confirmed its crucial role in the defense of rice seedlings. Enzymological characterization revealed that Gns6 preferentially hydrolyzed laminarin, pachymaran, and yeast glucan. The ß-1,3; 1,6-glucanase Gns6 exhibited a specific activity of 1.2 U/mg with laminarin as the substrate. In addition, Gns6 could hydrolyze laminarin via an endo-type mechanism, yielding a series of oligosaccharides with various degrees of polymerization that are known immune elicitors in plants. Moreover, Gns6 exhibited a significant inhibitory effect against the formation of the germ tubes and appressoria, with potential applications in plant protection. Taken together, this study shows that Gns6 is an essential effector in the defensive response of rice against pathogenic fungi.


Assuntos
Antifúngicos/farmacocinética , Magnaporthe/efeitos dos fármacos , Oryza/química , Oryza/genética , Doenças das Plantas/prevenção & controle , Extratos Vegetais/genética , Extratos Vegetais/metabolismo , Extratos Vegetais/farmacocinética , Regulação da Expressão Gênica de Plantas , Genes de Plantas
2.
Int J Biol Macromol ; 184: 551-557, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-34171255

RESUMO

Modified potato starch with slower digestion may aid the development of new starch derivatives with improved nutritional values, and strategies to increase nutritional fractions such as resistant starch (RS) are desired. In this study, a correspondence between starch structure and enzymatic resistance was provided based on the efficient branching enzyme AqGBE, and modified starches with different amylose content (Control, 100%; PS1, 90%; PS2, 72%; PS3, 32%; PS4, 18%) were prepared. Through SEM observation, NMR and X-ray diffraction analyses, we identified that an increased proportion of α-1,6-linked branches in potato starch changes its state of granule into large pieces with crystallinity. Molecular weight and chain-length distribution analysis showed a decrease of molecular weight (from 1.1 × 106 to 1.1 × 105 g/mol) without an obvious change of chain-length distribution in PS1, while PS2-4 exhibited an increased proportion of DP 6-12 with a stable molecular weight distribution, indicating a distinct model of structural modification by AqGBE. The enhancement of peak viscosity was related to increased hydrophobic interactions and pieces state of PS1, while the contents of SDS and RS in PS1 increased by 37.7 and 49.4%, respectively. Our result provides an alternative way to increase the RS content of potato starch by branching modification.


Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana/metabolismo , Burkholderiales/enzimologia , Solanum tuberosum/química , Amido/química , Amilose/química , Proteínas de Bactérias/metabolismo , Cristalografia por Raios X , Estrutura Molecular , Peso Molecular , Viscosidade , Difração de Raios X
3.
Protein Expr Purif ; 185: 105898, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33962003

RESUMO

Nutraceuticals containing modified starch with increased content of slowly-digestible starch (SDS) may reduce the prevalence of obesity, diabetes and cardiovascular diseases due to its slow digestion rate. Enzymatic methods for the preparation of modified starch have attracted increasing attention because of their low environmental impact, safety and specificity. In this study, the efficient glucan branching enzyme McGBE from Microvirga sp. MC18 was identified, and its relevant properties as well as its potential for industrial starch modification were evaluated. The purified McGBE exhibited the highest specificity for potato starch, with a maximal specific activity of 791.21 U/mg. A time-dependent increase in the content of α-1,6 linkages from 3.0 to 6.0% was observed in McGBE-modified potato starch. The proportion of shorter chains (degree of polymerization, DP < 13) increased from 29.2 to 63.29% after McGBE treatment, accompanied by a reduction of the medium length chains (DP 13-24) from 52.30 to 35.99% and longer chains (DP > 25) from 18.51 to 0.72%. The reduction of the storage modulus (G') and retrogradation enthalpy (ΔHr) of potato starch with increasing treatment time demonstrated that McGBE could inhibit the short- and long-term retrogradation of starch. Under the optimal conditions, the SDS content of McGBE-modified potato starch increased by 65.8% compared to native potato starch. These results suggest that McGBE has great application potential for the preparation of modified starch with higher SDS content that is resistant to retrogradation.


Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana/química , Proteínas de Bactérias/química , Suplementos Nutricionais/análise , Methylobacteriaceae/enzimologia , Amido/química , Enzima Ramificadora de 1,4-alfa-Glucana/genética , Enzima Ramificadora de 1,4-alfa-Glucana/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Clonagem Molecular , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Vetores Genéticos/metabolismo , Humanos , Hidrólise , Cinética , Methylobacteriaceae/química , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato
4.
Protein Expr Purif ; 179: 105798, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33232801

RESUMO

A pectinase-producing bacterial isolate, identified as Paenibacillus xylanexedens SZ 29, was screened by using the soil dilution plate with citrus pectin and congo red. A pectin methylesterase gene (Pxpme) was cloned and expressed in Escherichia coli. The gene coded for a protein with 334 amino acids and a calculated molecular mass of 36.76 kDa. PxPME showed the highest identity of 32.4% with the characterized carbohydrate esterase family 8 pectin methylesterase from Daucus carota. The recombined PxPME showed a specific activity with 39.38 U/mg against citrus pectin with >65% methylesterification. The optimal pH and temperature for PxPME activity were 5.0 and 45 °C. Its Km and Vmax value were determined to be 1.43 mg/mL and 71.5 µmol/mg·min, respectively. Moreover, PxPME could increase the firmness of pineapple cubes by 114% when combined with CaCl2. The acidic and mesophilic properties make PxPME a potential candidate for application in the fruit processing.


Assuntos
Proteínas de Bactérias , Hidrolases de Éster Carboxílico , Paenibacillus , Pectinas/metabolismo , Proteínas Recombinantes , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/genética , Hidrolases de Éster Carboxílico/metabolismo , Escherichia coli/genética , Manipulação de Alimentos , Frutas/química , Concentração de Íons de Hidrogênio , Paenibacillus/enzimologia , Paenibacillus/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Temperatura
5.
Int J Biol Macromol ; 145: 325-331, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31843609

RESUMO

Structural modification of starch using efficient α-amylases to improve its properties is an established method in the starch industry. In our previous research, the novel maltogenic α-amylase CoMA that catalyzes multi-molecular reactions has been identified. In this study, the impact of CoMA on the structure and retrogradation properties of potato starch was evaluated. CoMA cleaves internal starch chains to change the proportion of amylose and amylopectin in starch. Following treatment, visible pores and microporous on the surface of starch granules were observed from SEM analysis. CoMA modification led to increased insoluble blue complex formation and hydrolysis to shorten the outer chains, which was found to reduce the development rate of starch according to network interactions from the dynamic rheological analysis. Furthermore, maltose accumulation with water competition was also deduced to be involved in the inhibition of retrogradation. Its activities in the cleavage of internal starch granules, shortening of outer chains of starch, and maltose formation make CoMA a powerful agent for the inhibition of starch retrogradation with a very low effective dose of 0.5 mg/kg, which may find potential applications in the starch processing industry.


Assuntos
Proteínas de Bactérias/química , Solanum tuberosum/química , Amido/química , alfa-Amilases/química , Proteínas de Bactérias/isolamento & purificação , Tecnologia de Alimentos/métodos , Humanos , Hidrólise , Maltose/química , Myxococcales/química , Myxococcales/enzimologia , Porosidade , Solubilidade , Amido/isolamento & purificação , Água/química , alfa-Amilases/isolamento & purificação
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