Cornford E M, Fitzpatrick A M, Quirk T L, Diep C P, Landaw E M
Comprehensive Epilepsy Program, V. A. Wadsworth Medical Center, Los Angeles, California 90073.
J Parasitol. 1988 Feb;74(1):116-28.
Tegumental hexose transporters have been kinetically characterized in mated and separated male and female Schistosoma mansoni 8-12 wk postinfection. Significant gender-specific differences in Km and Vmax were observed. In mated males, the estimated constants (mean +/- SE) were: Km = 0.63 +/- 0.31 mM, Vmax = 0.93 +/- 0.44 nmol/mg worm water/min, and the Kd = 0.25 +/- 0.09 microliter/mg worm water/min. In mated females the kinetics were: Km = 0.99 +/- 0.40 mM, Vmax = 1.22 +/- 0.42 nmol/mg worm water/min, and Kd = 0.60 +/- 0.14 microliter/mg worm water/min. The influx of 2-deoxy-D-glucose and 3-O-methylglucose has been similarly characterized; these analogs share the same glucose transporter in male and female schistosomes. 2-Deoxy-D-glucose has a higher affinity, and 3-O-methylglucose a lower affinity, than does glucose. Because mated male schistosomes supply glucose to female partners, similarities between the free glucose concentration of the male and the affinity of the transporter determined for mated female schistosomes suggest that male-to-female transfer may be a potentially rate-limiting step in glucose utilization by the female. Permeability x surface are (PS) products and Vmax/Km ratios were significantly elevated in mated schistosomes, suggesting that the transporter is primarily localized to the dorsal surface of the male. Gender- and mating-specific analyses of PS products indicate that tegumental permeability to glucose is significantly increased in mated schistosomes, and compares very favorably to that of the host liver.
在感染后8 - 12周的已交配和未交配的曼氏血吸虫雌雄虫体中，对皮层己糖转运蛋白进行了动力学特征分析。观察到了Km和Vmax存在显著的性别特异性差异。在已交配的雄虫中，估算的常数（平均值±标准误）为：Km = 0.63±0.31 mM，Vmax = 0.93±0.44 nmol/（mg虫体湿重/分钟），Kd = 0.25±0.09 μl/（mg虫体湿重/分钟）。在已交配的雌虫中，动力学参数为：Km = 0.99±0.40 mM，Vmax = 1.22±0.42 nmol/（mg虫体湿重/分钟），Kd = 0.60±0.14 μl/（mg虫体湿重/分钟）。2 - 脱氧 - D - 葡萄糖和3 - O - 甲基葡萄糖的摄取也进行了类似的特征分析；这些类似物在雌雄血吸虫中共享相同的葡萄糖转运蛋白。2 - 脱氧 - D - 葡萄糖比葡萄糖具有更高的亲和力，而3 - O - 甲基葡萄糖比葡萄糖具有更低的亲和力。由于已交配的雄血吸虫会向雌虫伴侣供应葡萄糖，雄虫游离葡萄糖浓度与已交配雌血吸虫转运蛋白亲和力之间的相似性表明，雄虫向雌虫的葡萄糖转移可能是雌虫利用葡萄糖过程中一个潜在的限速步骤。已交配血吸虫的通透系数×表面积（PS）乘积和Vmax/Km比值显著升高，表明转运蛋白主要定位于雄虫的背表面。PS乘积的性别和交配特异性分析表明，已交配血吸虫的皮层对葡萄糖的通透性显著增加，与宿主肝脏的通透性相比非常有利。
