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L-阿拉伯糖异构酶对小鼠具有降血糖作用

The secreted L-arabinose isomerase displays anti-hyperglycemic effects in mice

Moez Rhimi, Luis G.Bermudez-Humaran, Yuan Huang, et al.

Rhimi et al. Microb Cell Fact (2015)14:204  DOI 10.1186/s12934-015-0391-5

Abstract

Background:The L-arabinose isomerase is an intracellular enzyme which converts L-arabinose into L-ribulose in living systems and D-galactose into D-tagatose in industrial processes and at industrial scales. D-tagatose is a natural ketohex-ose with potential uses in pharmaceutical and food industries. The D-galactose isomerization reaction is thermody-namically equilibrated, and leads to secondary subproducts at high pH. Therefore, an attractive L-arabinose isomerase should be thermoactive and acidotolerant with high catalytic efficiency. While many reports focused on the set out of a low cost process for the industrial production of D-tagatose, these procedures remain costly. When compared to intracellular enzymes, the production of extracellular ones constitutes an interesting strategy to increase the suitabil-ity of the biocatalysts.

Results:The L-arabinose isomerase (L-AI) from Lactobacillus sakei was expressed in Lactococcus lactis in fusion with the signal peptide of usp45 (SPUsp45). The L-AI protein and activity were detected only in the supernatant of the induced cultures of the recombinant L. lactis demonstrating the secretion in the medium of the intracellular L. sakeiL-AI in an active form. Moreover, we showed an improvement in the enzyme secretion using either (1) L. lactis strains deficient for their two major proteases, ClpP and HtrA, or (2) an enhancer of protein secretion in L. lactis fused to the recombinant L-AI with the SPUsp45. Th L-AI enzyme secreted by the recombinant L. lactis strains or produced intracel-lularly in E. coli, showed the same functional properties than the native enzyme. Furthermore, when mice are fed with the L. lactis strain secreting the L-AI and galactose, tagatose was produced invivo and reduced the glycemia index.

Conclusions:We report for the first time the secretion of the intracellular L-arabinose isomerase in the supernatant of food grade L. lactis cultures with hardly display other secreted proteins. The secreted L-AI originated from the food grade L. sakei 23K was active and showed the same catalytic and structural properties as the intracellular enzyme. The L. lactis strains secreting the L-arabinose isomerase has the ability to produce D-tagatose invivo and conferred an anti-hyperglycemic effect to mice.

Keywords:L-Arabinose isomerase, Secretion, Tagatose, Glycemia, Mice

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