Sofue M, Yoshimura Y, Nishida M, Kawada J
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
Biochem J. 1992 Dec 1;288 ( Pt 2)(Pt 2):669-74. doi: 10.1042/bj2880669.
A kinetic study of the uptake of nicotinamide by reconstituted liposomes containing the human erythrocyte glucose transporter, compared with that of D-glucose, demonstrated that the Km and Vmax. values were almost the same for each compound, and that the uptake of D-glucose was competitively inhibited by nicotinamide. At 20 mM concentration, 2-deoxy-D-glucose, 3-O-methyl-D-glucose and 4,6-O-ethylidene-D-glucose all caused 50% inhibition of nicotinamide uptake, but L-glucose and nicotinic acid were not inhibitory. Similar results were obtained for the uptake of D-glucose. Cytochalasin B binding to the liposomes was inhibited in a dose-dependent manner by either nicotinamide or D-glucose. Antibody for glucose transporter detected in band 4.5 by SDS/PAGE inhibited the uptake of D-glucose and nicotinamide. A possible uptake of nicotinamide by nucleoside transporter was excluded. In human erythrocytes, cytochalasin B binding was inhibited dose-dependently by either nicotinamide or D-glucose, and cytochalasin B depressed the uptake of both nicotinamide and 2-deoxy-D-glucose. These findings were well reproduced in the reconstituted liposomes. The very close similarities between uptake of nicotinamide and D-glucose suggest that the glucose transporter plays a direct role in transport of nicotinamide, which is structurally quite different from monosaccharides, and thus that the transporter is probably multifunctional.
一项关于含有人红细胞葡萄糖转运蛋白的重构脂质体摄取烟酰胺的动力学研究，与D - 葡萄糖的摄取情况相比，结果表明每种化合物的Km和Vmax值几乎相同，并且烟酰胺竞争性抑制D - 葡萄糖的摄取。在20 mM浓度下，2 - 脱氧 - D - 葡萄糖、3 - O - 甲基 - D - 葡萄糖和4,6 - O - 亚乙基 - D - 葡萄糖均导致烟酰胺摄取受到50%的抑制，但L - 葡萄糖和烟酸没有抑制作用。D - 葡萄糖摄取也得到了类似结果。细胞松弛素B与脂质体的结合受到烟酰胺或D - 葡萄糖的剂量依赖性抑制。通过SDS/PAGE在4.5条带中检测到的葡萄糖转运蛋白抗体抑制了D - 葡萄糖和烟酰胺的摄取。排除了核苷转运蛋白摄取烟酰胺的可能性。在人红细胞中，细胞松弛素B的结合受到烟酰胺或D - 葡萄糖的剂量依赖性抑制，并且细胞松弛素B降低了烟酰胺和2 - 脱氧 - D - 葡萄糖的摄取。这些发现可以在重构脂质体中很好地重现。烟酰胺和D - 葡萄糖摄取之间非常相似，这表明葡萄糖转运蛋白在结构与单糖有很大不同的烟酰胺转运中起直接作用，因此该转运蛋白可能具有多种功能。
