Boles E, Hollenberg C P
Institut für Mikrobiologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
FEMS Microbiol Rev. 1997 Aug;21(1):85-111. doi: 10.1111/j.1574-6976.1997.tb00346.x.
Transport across the plasma membrane is the first, obligatory step of hexose utilization. In yeast cells the uptake of hexoses is mediated by a large family of related transporter proteins. In baker's yeast Saccharomyces cerevisiae the genes of 20 different hexose transporter-related proteins have been identified. Six of these transmembrane proteins mediate the metabolically relevant uptake of glucose, fructose and mannose for growth, two others catalyze the transport of only small amounts of these sugars, one protein is a galactose transporter but also able to transport glucose, two transporters act as glucose sensors, two others are involved in the pleiotropic drug resistance process, and the functions of the remaining hexose transporter-related proteins are not yet known. The catabolic hexose transporters exhibit different affinities for their substrates, and expression of their corresponding genes is controlled by the glucose sensors according to the availability of carbon sources. In contrast, milk yeast Kluyveromyces lactis contains only a few different hexose transporters. Genes of other monosaccharide transporter-related proteins have been found in fission yeast Schizosaccharomyces pombe and in the xylose-fermenting yeast Pichia stipitis. However, the molecular genetics of hexose transport in many other yeasts remains to be established. The further characterization of this multigene family of hexose transporters should help to elucidate the role of transport in yeast sugar metabolism.
跨质膜转运是己糖利用的第一步，也是必不可少的一步。在酵母细胞中，己糖的摄取由一大类相关的转运蛋白介导。在面包酵母酿酒酵母中，已鉴定出20种不同的与己糖转运蛋白相关的蛋白质的基因。其中六种跨膜蛋白介导葡萄糖、果糖和甘露糖的代谢相关摄取以促进生长，另外两种仅催化少量这些糖类的转运，一种蛋白质是半乳糖转运蛋白但也能够转运葡萄糖，两种转运蛋白充当葡萄糖传感器，另外两种参与多药耐药过程，其余与己糖转运蛋白相关的蛋白质的功能尚不清楚。分解代谢的己糖转运蛋白对其底物表现出不同的亲和力，并且它们相应基因的表达由葡萄糖传感器根据碳源的可用性来控制。相比之下，乳酵母乳酸克鲁维酵母仅含有几种不同的己糖转运蛋白。在裂殖酵母粟酒裂殖酵母和木糖发酵酵母树干毕赤酵母中发现了其他与单糖转运蛋白相关的蛋白质的基因。然而，许多其他酵母中己糖转运的分子遗传学仍有待确定。对这个己糖转运蛋白多基因家族的进一步表征应该有助于阐明转运在酵母糖代谢中的作用。
