Pico C, Pons A, Palou A
Departament de Biologia Fonamental i Ciències de la Salut, Universitat de les Illes Balears, Palma de Mallorca, Spain.
Int J Biochem Cell Biol. 1995 Aug;27(8):761-5. doi: 10.1016/1357-2725(95)00049-u.
Amino acids adsorbed onto blood cell membranes represent about 8% of the total amino acids in blood. The aim of this study was to determine the in vitro adsorption kinetics of different amino acids (L-alanine, glycine, L-glutamate, L-glutamine, L-phenylalanine and L-leucine) onto rat erythrocyte membranes and to assess the effect of 24-hr starvation on these adsorption kinetics. Isolated red cell membranes were incubated at 37 degrees C for 10 sec in the presence of 14C-amino acids--with different specific radioactivity--the radioactivity retained in the membrane fraction measured and kinetic parameters of amino acid adsorption determined. With the exception of glutamate, where the adsorption was negligible, all amino acids studied were adsorbed onto isolated red cell membranes, adhering to simple Michaelis-Menten kinetics. Km' values of glycine, phenylalanine and leucine adsorption in control rats (14.7 +/- 3.8 mM, 8.41 +/- 0.95 mM and 4.65 +/- 0.46 mM respectively, SEM, n = 6-8) decreased in response to 24-hr starvation, giving the following values: 0.792 +/- 0.122 mM, 5.32 +/- 0.82 mM and 3.53 +/- 0.31 mM respectively (SEM, n = 6-8), Vmax' value of glycine adsorption of control rats decreased (from 61.0 +/- 15.5 mmol/mol P/sec to 4.25 +/- 0.70 mmol/mol P/sec, SEM, n = 7) and that of leucine increased (from 13.5 +/- 1.0 mmol/mol P/sec to 18.9 +/- 2.0 mmol/mol P/sec, SEM, n = 7) as an effect of 24-hr starvation. This study shows that alanine, glycine, glutamine, phenylalanine and leucine, but not glutamate, adsorbed onto erythrocyte membranes according to Michaelis-Menten-like kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)
吸附在血细胞细胞膜上的氨基酸约占血液中总氨基酸的8%。本研究的目的是测定不同氨基酸（L-丙氨酸、甘氨酸、L-谷氨酸、L-谷氨酰胺、L-苯丙氨酸和L-亮氨酸）在大鼠红细胞膜上的体外吸附动力学，并评估24小时饥饿对这些吸附动力学的影响。将分离的红细胞膜在37℃下于含有不同比放射性的14C-氨基酸存在下孵育10秒，测量保留在膜部分的放射性，并确定氨基酸吸附的动力学参数。除谷氨酸的吸附可忽略不计外，所有研究的氨基酸均吸附在分离的红细胞膜上，遵循简单的米氏动力学。对照大鼠中甘氨酸、苯丙氨酸和亮氨酸吸附的Km'值（分别为14.7±3.8 mM、8.41±0.95 mM和4.65±0.46 mM，标准误，n = 6 - 8）在24小时饥饿后降低，分别为0.792±0.122 mM、5.32±0.82 mM和3.53±0.31 mM（标准误，n = 6 - 8），对照大鼠中甘氨酸吸附的Vmax'值降低（从61.0±15.5 mmol/mol P/秒降至4.25±0.70 mmol/mol P/秒，标准误，n = 7），而亮氨酸的Vmax'值增加（从13.5±1.0 mmol/mol P/秒增至18.9±2.0 mmol/mol P/秒，标准误，n = 7），这是24小时饥饿的影响。本研究表明，丙氨酸、甘氨酸、谷氨酰胺、苯丙氨酸和亮氨酸（而非谷氨酸）按照类似米氏的动力学吸附在红细胞膜上。（摘要截断于250字）
