Centre of Environmental and Molecular Biology, Department of Biology, University of Minho, Campus of Gualtar, 4710-057 Braga, Portugal.
School of Microbiology, Centre for Synthetic Biology and Biotechnology, Environmental Research Institute, APC Microbiome Institute, University College Cork, T12YT20 Cork, Ireland.
FEMS Yeast Res. 2020 Feb 1;20(1). doi: 10.1093/femsyr/foaa004.
Torulaspora delbrueckii is a yeast species receiving increasing attention from the biotechnology industry, with particular relevance in the wine, beer and baking sectors. However, little is known about its sugar transporters and sugar transport capacity, frequently a rate-limiting step of sugar metabolism and efficient fermentation. Actually, only one glucose transporter, Lgt1, has been characterized so far. Here we report the identification and characterization of a second glucose transporter gene, IGT1, located in a cluster, upstream of LGT1 and downstream of two other putative hexose transporters. Functional characterization of IGT1 in a Saccharomyces cerevisiae hxt-null strain revealed that it encodes a transporter able to mediate uptake of glucose, fructose and mannose and established that its affinity, as measured by Km, could be modulated by glucose concentration in the medium. In fact, IGT1-transformed S. cerevisiae hxt-null cells, grown in 0.1% glucose displayed biphasic glucose uptake kinetics with an intermediate- (Km = 6.5 ± 2.0 mM) and a high-affinity (Km = 0.10 ± 0.01 mM) component, whereas cells grown in 2% glucose displayed monophasic kinetics with an intermediate-affinity (Km of 11.5 ± 1.5 mM). This work contributes to a better characterization of glucose transport in T. delbrueckii, with relevant implications for its exploitation in the food industry.
毕赤酵母是一种受到生物技术行业越来越多关注的酵母物种，特别是在葡萄酒、啤酒和烘焙领域。然而，人们对其糖转运蛋白和糖转运能力知之甚少，而这些通常是糖代谢和高效发酵的限速步骤。实际上，到目前为止，只鉴定出了一种葡萄糖转运蛋白 Lgt1。在这里，我们报道了第二种葡萄糖转运蛋白基因 IGT1 的鉴定和特性，该基因位于 Lgt1 的上游和两个假定的六碳糖转运蛋白的下游的一个基因簇中。在 Saccharomyces cerevisiae hxt-null 菌株中对 IGT1 的功能进行了表征，结果表明它编码一种能够介导葡萄糖、果糖和甘露糖摄取的转运蛋白，并证实其亲和力（Km 表示）可以通过培养基中的葡萄糖浓度来调节。事实上，在 0.1%葡萄糖中生长的 IGT1 转化的 S. cerevisiae hxt-null 细胞表现出双相葡萄糖摄取动力学，具有中间亲和力（Km = 6.5 ± 2.0 mM）和高亲和力（Km = 0.10 ± 0.01 mM）组分，而在 2%葡萄糖中生长的细胞表现出单相动力学，具有中间亲和力（Km 为 11.5 ± 1.5 mM）。这项工作有助于更好地描述毕赤酵母中的葡萄糖转运，对其在食品工业中的利用具有重要意义。
