Eksittikul T, Chulavatnatol M, Limpaseni T
Department of Biochemistry, Faculty of Science, Chulalongkorn University, 10330, Bangkok, Thailand
Plant Sci. 2001 Mar;160(4):733-737. doi: 10.1016/s0168-9452(00)00455-6.
A leaf disc system was developed to study sucrose uptake in cassava (Manihot esculenta Crantz). The uptake of (U-(14)C) sucrose by cassava leaf discs followed Michaelis-Menten kinetics with a K(m) value for sucrose of 1.3 mM. It was found to be strongly inhibited by sulfhydryl reagents, N-ethylmaleimide, p-chloromercuribenzene sulfonate and iodoacetate. Several metabolic inhibitors were also tested. Among these, dinitrophenol, chlorocarbonyl cyanide phenylhydrazone, phloridzin and vanadate inhibited the sucrose uptake by the leaf discs. Linamarin, the main cassava cyanogenic glucoside, strongly inhibited the sucrose uptake by the leaf discs, while other cyanogenic glycosides tested (prunasin and amygdalin) showed a much weaker inhibition. A linamarin analog, isopropylthioglucoside, was a weaker inhibitor than p-nitrophenyl glucosides (both alpha and beta forms). Cassava root discs were also capable of taking up sucrose, but linamarin activated its uptake. The observations suggested that linamarin may regulate the sucrose transport in cassava.
开发了一种叶盘系统来研究木薯（Manihot esculenta Crantz）对蔗糖的吸收。木薯叶盘对（U-(14)C）蔗糖的吸收遵循米氏动力学，蔗糖的K(m)值为1.3 mM。发现它受到巯基试剂、N-乙基马来酰亚胺、对氯汞苯磺酸盐和碘乙酸的强烈抑制。还测试了几种代谢抑制剂。其中，二硝基苯酚、羰基氰化物间氯苯腙、根皮苷和钒酸盐抑制叶盘对蔗糖的吸收。木薯主要的含氰糖苷亚麻苦苷强烈抑制叶盘对蔗糖的吸收，而测试的其他含氰糖苷（樱草糖苷和苦杏仁苷）的抑制作用则弱得多。亚麻苦苷类似物异丙基硫代葡萄糖苷的抑制作用比对硝基苯基葡萄糖苷（α和β两种形式）弱。木薯根盘也能够吸收蔗糖，但亚麻苦苷能激活其吸收。这些观察结果表明，亚麻苦苷可能调节木薯中的蔗糖运输。
