RESUMEN
The gene encoding an α-L-arabinofuranosidase (BvAF) GH51 from Bacillus velezensis FZB42 was cloned and expressed in Escherichia coli. The corresponding open reading frame consists of 1,491 nucleotides which encode 496 amino acids with the molecular mass of 56.9 kDa. BvAF showed the highest activity against sugar beet (branched) arabinan in 50 mM sodium acetate buffer (pH 6.0) at 45°C. However, it could hardly hydrolyze debranched arabinan and arabinoxylans. The time-course hydrolyses of branched arabinan and arabinooligosaccharides (AOS) revealed that BvAF is a unique exo-hydrolase producing exclusively L-arabinose. BvAF could cleave α-(1,2)- and/or α-(1,3)-L-arabinofuranosidic linkages of the branched substrates to produce the debranched forms of arabinan and AOS. Although the excessive amount of BvAF could liberate L-arabinose from linear AOS, it was extremely lower than that on branched AOS. In conclusion, BvAF is the arabinan-specific exo-acting α-L-arabinofuranosidase possessing high debranching activity towards α-(1,2)- and/or α-(1,3)-linked branches of arabinan, which can facilitate the successive degradation of arabinan by endo-α-(1,5)-L-arabinanase.
Asunto(s)
Bacillus/enzimología , Proteínas Bacterianas/metabolismo , Glicósido Hidrolasas/metabolismo , Polisacáridos/metabolismo , Secuencia de Aminoácidos , Arabinosa/metabolismo , Bacillus/genética , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Proteínas Bacterianas/aislamiento & purificación , Beta vulgaris/química , Clonación Molecular , Escherichia coli/enzimología , Escherichia coli/genética , Expresión Génica , Glicósido Hidrolasas/química , Glicósido Hidrolasas/genética , Glicósido Hidrolasas/aislamiento & purificación , Concentración de Iones de Hidrógeno , Hidrólisis , Cinética , Peso Molecular , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/metabolismo , Especificidad por Sustrato , TemperaturaRESUMEN
BACKGROUND: There is no approved therapy for patients with failed transarterial chemoembolization (TACE) and progression of hepatocellular carcinoma. We aimed to investigate the efficacy and prognostic factors in patients with TACE failure who received sorafenib rescue therapy. METHODS: We investigated 54 patients who met the criteria of TACE failure as defined by the international guidelines of Europe and Japan. Sorafenib was used as a rescue therapy. Overall survival (OS) and progression-free survival (PFS) were analyzed by Kaplan-Meier methods, and multivariate analysis was performed to find prognostic factors. RESULTS: The patients were followed for a median 5.5 months, and the median duration of sorafenib administration was 3.3 months. The presence of main (or lobar) portal vein invasion (PVI) (3.7 versus 8.4 months, p = 0.004), dose reduction of sorafenib (4.0 versus 8.8 months, p = 0.002) and Child-Pugh class B (5.3 versus 8.9 months, p = 0.004) were associated with shorter OS compared to the presence of segmental PVI (or absence of macroscopic vascular invasion, MVI), full dosage of sorafenib and Child-Pugh class A, respectively. The presence of main (or lobar) PVI was associated with poorer PFS compared to the presence of segmental PVI (or absence of MVI) (2.1 versus 3.8 months p = 0.010). CONCLUSIONS: Sorafenib is a potential rescue therapy in patients with TACE failure. However, the clinical benefits need to be further evaluated for patients with main (or lobar) PVI or those treated with reduced doses of sorafenib.
Asunto(s)
Carcinoma Hepatocelular/tratamiento farmacológico , Neoplasias Hepáticas/tratamiento farmacológico , Niacinamida/análogos & derivados , Compuestos de Fenilurea/farmacología , Vena Porta/patología , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma Hepatocelular/patología , Quimioembolización Terapéutica/métodos , Progresión de la Enfermedad , Supervivencia sin Enfermedad , Femenino , Humanos , Neoplasias Hepáticas/patología , Masculino , Persona de Mediana Edad , Invasividad Neoplásica , Niacinamida/administración & dosificación , Niacinamida/efectos adversos , Niacinamida/farmacología , Compuestos de Fenilurea/administración & dosificación , Compuestos de Fenilurea/efectos adversos , Pronóstico , Inhibidores de Proteínas Quinasas/uso terapéutico , Estudios Retrospectivos , Sorafenib , Insuficiencia del Tratamiento , Resultado del TratamientoRESUMEN
This study was conducted to investigate the prebiotic effects of linear arabino-oligosaccharides (LAOS) and debranched (linear) sugar beet arabinan (LAR) for the development of new prebiotics. LAOS were prepared from LAR by enzymatic hydrolysis with endo-arabinanase from Bacillus licheniformis, followed by removal of the arabinose fraction by incubation with resting cells of Leuconostoc mesenteroides. The resulting LAOS contained DP2 (28.7%), DP3 (49.9%), DP4 (20.1%), and DP5 (1.16%). A standardized digestibility test showed that LAOS and LAR were not digestible. Individual cultures of 24 strains of gastrointestinal bacteria showed that LAOS and LAR stimulated growth of Lactobacillus brevis, Bifidobacterium longum, and Bacteroides fragilis. In vitro batch fermentation using human fecal samples showed that LAOS had higher bifidogenic properties than LAR; LAOS increased the population of bifidobacteria which produced short-chain fatty acids (SCFAs). LAOS was fermented slowly compared to fructo-oligosaccharides and this may permit SCFA production in the distal colon. This study demonstrates that LAOS prepared from LAR are promising dietary substrates for improvement of human intestinal health.
Asunto(s)
Beta vulgaris/química , Fermentación , Oligosacáridos/metabolismo , Polisacáridos/metabolismo , Bacterias/crecimiento & desarrollo , Bacterias/metabolismo , Ácidos Grasos Volátiles/análisis , Heces/microbiología , Humanos , Concentración de Iones de Hidrógeno , Intestinos/microbiología , Ácido Láctico/metabolismo , Prebióticos , Análisis de Componente PrincipalRESUMEN
Two recombinant arabinosyl hydrolases, α-L-arabinofuranosidase from Geobacillus sp. KCTC 3012 (GAFase) and endo-(1,5)-α-L-arabinanase from Bacillus licheniformis DSM13 (BlABNase), were overexpressed in Escherichia coli, and their synergistic modes of action against sugar beet (branched) arabinan were investigated. Whereas GAFase hydrolyzed 35.9% of L-arabinose residues from sugar beet (branched) arabinan, endo-action of BlABNase released only 0.5% of L-arabinose owing to its extremely low accessibility towards branched arabinan. Interestingly, the simultaneous treatment of GAFase and BlABNase could liberate approximately 91.2% of L-arabinose from arabinan, which was significantly higher than any single exo-enzyme treatment (35.9%) or even stepwise exo- after endo-enzyme treatment (75.5%). Based on their unique modes of action, both exo- and endo-arabinosyl hydrolases can work in concert to catalyze the hydrolysis of arabinan to L-arabinose. At the early stage in arabinan degradation, exo-acting GAFase could remove the terminal arabinose branches to generate debranched arabinan, which could be successively hydrolyzed into arabinooligosaccharides via the endoaction of BlABNase. At the final stage, the simultaneous actions of exo- and endo-hydrolases could synergistically accelerate the L-arabinose production with high conversion yield.