Johnstone R M
Can J Biochem Cell Biol. 1983 Apr;61(4):165-70. doi: 10.1139/o83-024.
Many hydrophilic amino acids are transported via exchange by the Na+-independent L system in the Ehrlich cells. However, this exchange is measurable only at relative high concentrations of the small hydrophilic amino acids. Whereas leucine saturated this transport system at 0.2 mM, with threonine, serine, or alanine the system was below saturation at 30 mM. All amino acids capable of exchanging showed similar EA values (congruent to 20 X 10(3) cal X mol-1, 1 cal = 4.1868 J) and maximum velocities. Depending on the temperature, the apparent Km values for different amino acids differed by one or two orders of magnitude. These data suggest that for the small hydrophilic amino acids, the relatively slow rate of transport is due to the unfavorable Km values.
许多亲水性氨基酸通过埃利希细胞中不依赖钠离子的L系统进行交换运输。然而，这种交换只有在相对高浓度的小亲水性氨基酸时才可测量。亮氨酸在0.2 mM时使该转运系统饱和，而苏氨酸、丝氨酸或丙氨酸在30 mM时该系统仍未饱和。所有能够进行交换的氨基酸都表现出相似的EA值（约为20×10³ cal·mol⁻¹，1 cal = 4.1868 J）和最大速度。根据温度不同，不同氨基酸的表观Km值相差一到两个数量级。这些数据表明，对于小亲水性氨基酸来说，相对较慢的运输速率是由于不利的Km值所致。
