Ladyzhenskaia E P, Sukhova L S, Korableva N P, Metlitskiĭ L V
Biokhimiia. 1982 Jan;47(1):66-70.
The uptake of 14C-L-leucine by the points of growth separated from potato tubers was studied. The pH optimum of the process was about 7.0. The leucine transport over a wide concentration range was biphasic. For descriptive convenience the isotherm was divided into two segments, both of which obeyed the Michaelis-Menten kinetics. The Km value for the high affinity transport was within the range of 7.0 x 10(-6) mM, while that for the low affinity transport was within the range of 5 x 10(-4) mM. The maximum velocities were 3 x 10(-8) mM/g of dry weight/hour and 3.8 x 10(-7) mM/g of dry weight/hour, respectively. Cycloheximide and 2.4-dinitroftorphenol caused a considerable inhibition of net transport of L-leucine, while actinomycin D had no such effect. The uptake of L-leucine was unaffected by phenylalanine and isoleucine, but was strongly inhibited by D-leucine. The results obtained are indicative of a biphasic carrier-mediated uptake system with a high affinity and high substrate specificity for leucine.
研究了从马铃薯块茎分离出的生长点对14C-L-亮氨酸的摄取情况。该过程的最适pH约为7.0。在较宽浓度范围内亮氨酸的转运呈双相性。为便于描述，等温线分为两段，两段均符合米氏动力学。高亲和力转运的Km值在7.0×10(-6) mM范围内，而低亲和力转运的Km值在5×10(-4) mM范围内。最大速度分别为3×10(-8) mM/干重/小时和3.8×10(-7) mM/干重/小时。环己酰亚胺和2,4-二硝基氟苯对L-亮氨酸的净转运有显著抑制作用，而放线菌素D则无此作用。L-亮氨酸的摄取不受苯丙氨酸和异亮氨酸的影响，但受到D-亮氨酸的强烈抑制。所得结果表明存在一种双相载体介导的摄取系统，对亮氨酸具有高亲和力和高底物特异性。
