Rolim M F, de Araujo P S, Panek A D, Paschoalin V M F, Silva J T
Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brasil.
Braz J Med Biol Res. 2003 Jul;36(7):829-37. doi: 10.1590/s0100-879x2003000700002. Epub 2003 Jun 26.
Trehalose biosynthesis and its hydrolysis have been extensively studied in yeast, but few reports have addressed the catabolism of exogenously supplied trehalose. Here we report the catabolism of exogenous trehalose by Candida utilis. In contrast to the biphasic growth in glucose, the growth of C. utilis in a mineral medium with trehalose as the sole carbon and energy source is aerobic and exhibits the Kluyver effect. Trehalose is transported into the cell by an inducible trehalose transporter (K M of 8 mM and V MAX of 1.8 mol trehalose min-1 mg cell (dry weight)-1. The activity of the trehalose transporter is high in cells growing in media containing trehalose or maltose and very low or absent during the growth in glucose or glycerol. Similarly, total trehalase activity was increased from about 1.0 mU/mg protein in cells growing in glucose to 39.0 and 56.2 mU/mg protein in cells growing in maltose and trehalose, respectively. Acidic and neutral trehalase activities increased during the growth in trehalose, with neutral trehalase contributing to about 70% of the total activity. In addition to the increased activities of the trehalose transporter and trehalases, growth in trehalose promoted the increase in the activity of alpha-glucosidase and the maltose transporter. These results clearly indicate that maltose and trehalose promote the increase of the enzymatic activities necessary to their catabolism but are also able to stimulate each other's catabolism, as reported to occur in Escherichia coli. We show here for the first time that trehalose induces the catabolism of maltose in yeast.
海藻糖的生物合成及其水解在酵母中已得到广泛研究，但关于外源供应海藻糖的分解代谢的报道却很少。在此，我们报道了产朊假丝酵母对外源海藻糖的分解代谢。与在葡萄糖中双相生长不同，产朊假丝酵母在以海藻糖作为唯一碳源和能源的矿物培养基中生长是需氧的，并表现出克鲁维效应。海藻糖通过一种可诱导的海藻糖转运蛋白转运进入细胞（米氏常数为8 mM，最大反应速度为1.8摩尔海藻糖每分钟每毫克细胞（干重））。海藻糖转运蛋白的活性在含有海藻糖或麦芽糖的培养基中生长的细胞中较高，而在葡萄糖或甘油中生长时则非常低或不存在。同样，总海藻糖酶活性从在葡萄糖中生长的细胞中的约1.0 mU/mg蛋白质分别增加到在麦芽糖和海藻糖中生长的细胞中的39.0和56.2 mU/mg蛋白质。酸性和中性海藻糖酶活性在海藻糖生长过程中增加，其中中性海藻糖酶约占总活性的70%。除了海藻糖转运蛋白和海藻糖酶活性增加外，在海藻糖中生长还促进了α-葡萄糖苷酶和麦芽糖转运蛋白活性的增加。这些结果清楚地表明，麦芽糖和海藻糖促进了其分解代谢所需酶活性的增加，但也能够相互刺激对方的分解代谢，正如在大肠杆菌中所报道的那样。我们在此首次表明，海藻糖可诱导酵母中麦芽糖的分解代谢。
