皮状丝孢酵母同步利用葡萄糖/木糖的糖转运动力学

Kinetics of sugar transport by Trichosporon cutaneum using simultaneous utilization of glucose and xylose

皮状丝孢酵母(Trichosporon cutaneum)能够同步利用葡萄糖和木糖生产油脂。以2-脱氧葡萄糖(2-DOG)为底物,考察皮状丝孢酵母糖跨膜运输的转运动力学。结果表明:2-DOG转运符合米氏方程,表观米氏常数K m为0.19 mmol/L,最大转运速率V max为14.1 nmol/(min·mg)。葡萄糖和木糖均竞争性抑制2-DOG转运,葡萄糖表观抑制常数K i远低于木糖,表明存在一个共用转运体系,且该转运体系对葡萄糖亲和力更高。大量木糖与2-DOG同时转运到胞内,进一步说明木糖与葡萄糖共运输。代谢抑制剂和pH对糖转运有明显影响,说明质子/底物同向运输系统是该酵母的主要糖转运系统。

The yeast Trichosporon cutaneum can utilize glucose and xylose simultaneously for microbial lipid production. The sugar transport kinetics was studied by using 2-deoxyglucose （ 2-DOG ） as a surrogate substrate.It was found that kinetics data of 2-DOG transport fitted well to Michaelis-Menten plot and that the apparent Km of 0.19 mmol/L and Vmax of 14.1 nmol/（ min＆#183;mg） were obtained.Both glucose and xylose inhibited competitively the transport of 2-DOG, indicating that these compounds shared the same transporter.The apparent inhibition constant Ki of glucose was much lower than that of xylose, suggesting a higher affinity of the transporter to glucose than xylose.The fact that large amount of xylose was uptaken together with 2-DOG further supported the co-transport of glucose and xylose.As 2-DOG transport was sensitive to metabolic inhibitors and pH,an H＋/sugar-symport system was suggested as the main sugar transporter.