Barnett J E, Ralph A, Munday K A
Biochem J. 1970 Aug;118(5):843-50. doi: 10.1042/bj1180843.
Several weakly transported sugars were tested for transport by the Na(+)-dependent sugar carrier with slices of everted hamster intestinal tissue. Sugars were assumed to be transported by this carrier if the accumulation was diminished in the absence of Na(+) and in the presence of the competitive inhibitor 1,5-anhydro-d-glucitol. The extent of accumulation was correlated with the number of hydroxyl groups in the d-gluco configuration if the ring oxygen was placed in the normal d-glucose position. 5-Thio-d-glucose, with a sulphur atom in the ring, was transported at about the same rate as d-glucose and had a similar K(i) for d-galactose transport, but myoinositol was poorly accumulated. It is suggested that there is no hydrogen bonding at the ring oxygen atom, but that the oxygen atom is found at this position as a result of steric constraints. No sugar without a hydroxyl group in the d-gluco position at C-2 of the sugar, including d-mannose, 2-deoxy-d-glucose, 2-chloro-2-deoxy-d-glucose and 2-deoxy-2-fluoro-d-glucose, was transported by the Na(+)-dependent carrier, but these sugars and l-fucose weakly and competitively inhibit the Na(+)-dependent accumulation of l-glucose into slices of everted hamster intestinal tissue. It is concluded that the bond between the carrier and C-2 of the sugar may be covalent, and a possible mechanism for active intestinal transport is proposed.
用外翻的仓鼠肠组织切片，通过钠依赖性糖载体对几种转运较弱的糖类进行了转运测试。如果在无钠存在以及有竞争性抑制剂1,5 - 脱水 - d - 葡萄糖醇存在时积累减少，则假定糖类是由该载体转运的。如果环氧化合物处于正常d - 葡萄糖位置，积累程度与d - 葡萄糖构型中的羟基数量相关。5 - 硫代 - d - 葡萄糖在环中有一个硫原子，其转运速率与d - 葡萄糖大致相同，对d - 半乳糖转运具有相似的抑制常数（Ki），但肌醇积累较差。有人认为在环氧化合物原子处不存在氢键，而是由于空间位阻，氧原子处于该位置。没有一种在糖的C - 2位d - 葡萄糖位置没有羟基的糖，包括d - 甘露糖、2 - 脱氧 - d - 葡萄糖、2 - 氯 - 2 - 脱氧 - d - 葡萄糖和2 - 脱氧 - 2 - 氟 - d - 葡萄糖，能被钠依赖性载体转运，但这些糖和L - 岩藻糖能微弱且竞争性地抑制L - 葡萄糖向外翻的仓鼠肠组织切片中的钠依赖性积累。得出结论，载体与糖的C - 2之间的键可能是共价键，并提出了一种肠道主动转运的可能机制。
