Glucose transport in Cladosporium resinae was studies with the aid of the non-metabolizable glucose analogue 3-O-methyl-D-glucose (3-O-MG). 3-O-MG, transported as a free sugar without phosphorylation, was found to inhibit glucose uptake competitively. Conversely, glucose was a competitive inhibitor of 3-O-MG uptake. Moreover, both glucose and 3-O-MG were able to bring about rapid counterflow intracellular 3-O-MG. Thus, glucose and 3-O-MG share the same entry and exit systems. The transport of 3-O-MG is carrier mediated and energy dependent as shown by saturation kinetics, strong temperature dependence, accumulation of unaltered 3-O-MG against a concentration gradient, and inhibition of uptake by NaN3, NaCN, and 2,4-dinitrophenol. The glucose transport system appeared to be constitutive for glucose transport in cells grown on fructose, galactose, mannose, xylose, or glucose. There was no derepressible low-Km glucose transport system in C. resinae. n-Hexane and n-heptane were found to inhibit 3-O-MG uptake rapidly at temperatures above 20 C. Over 50% inhibition of the uptake rate occurred after only 10 min of incubation with n-hexane at 30 C. The percentage of inhibition in the presence of n-hexane, compared to controls in the absence of n-hexane, was found to increase with increasing temperature. Longer-chain n-alkanes (C8 to C18) had no significant effect on uptake. The efflux of intracellular 3-O-MG, which appeared to occur by facilitated diffusion, was not affected by any of the n-alkanes tested including n-hexane.

译文

借助不可代谢的葡萄糖类似物3-o-甲基-d-葡萄糖 (3-o-mg) 研究了树脂枝孢菌中的葡萄糖转运。发现3-O-MG以游离糖的形式运输而没有磷酸化,可以竞争性地抑制葡萄糖的摄取。相反,葡萄糖是3-O-MG摄取的竞争性抑制剂。此外,葡萄糖和3-O-MG都能带来细胞内3-O-MG的快速逆流。因此,葡萄糖和3-O-MG共享相同的进入和退出系统。3-O-MG的转运是载体介导的,并且取决于能量,如饱和动力学,强烈的温度依赖性,相对于浓度梯度未改变的3-O-MG的积累以及对NaN3,NaCN和2,4-的吸收的抑制。二硝基苯酚。葡萄糖转运系统似乎是在果糖,半乳糖,甘露糖,木糖或葡萄糖上生长的细胞中葡萄糖转运的组成部分。树脂中没有不可抑制的低Km葡萄糖转运系统。发现正己烷和正庚烷在高于20 °c的温度下会迅速抑制3-O-MG的吸收。在30 °c下与正己烷孵育仅10分钟后,对摄取速率的50% 抑制发生。发现与不存在正己烷的对照相比,在正己烷存在下的抑制百分比随温度升高而增加。长链正构烷烃 (C8至C18) 对吸收没有显着影响。细胞内3-O-MG的流出似乎是通过促进扩散而发生的,不受任何测试的正构烷烃 (包括正己烷) 的影响。

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