Kandpal M, Fouce R B, Pal A, Guru P Y, Tekwani B L
Division of Biochemistry, Central Drug Research Institute, Lucknow, India.
Mol Biochem Parasitol. 1995 May;71(2):193-201. doi: 10.1016/0166-6851(95)00042-y.
Characteristics of transport of L-arginine were studied in Leishmania donovani promastigotes grown in vitro in a defined medium. The promastigotes exhibited a time-dependent, temperature-sensitive, pH-dependent and saturable uptake of arginine. Metabolic inhibitors caused 81-92% inhibition, indicating that arginine influx in promastigotes is an energy requiring process. The presence of Na+ ions was necessary for full activity. Considerable inhibition was also noticed with valinomycin, gramicidin and amiloride. The transporter seems to involve an -SH group at the active site. The most distinctive feature of the leishmanial transporter was that lysine and ornithine did not show significant competition with arginine transport. Other neutral and acidic amino acids, as well as polyamines were also ineffective. The arginine analogues, viz., nitro-L-arginine methyl ester, N-nitro-L-arginine, aminoguanidine, agmatine and D-arginine were not recognised by the transporter, while N-methyl-L-arginine acetate and phospho-L-arginine showed competition, indicating stereo-specificity of the transporter and recognition of both the guanidino group, as well as the arginine side chain by the transporter. No exchange of intracellular [14C]arginine taken up by the promastigotes was noticed during incubation with 2 or 5 mM arginine in the extracellular medium. Eighty percent of the arginine taken up remained in the trichloroacetic acid-soluble fraction. Pentamidine caused competitive inhibition of arginine transport, exhibiting an IC50 value of 40 microM. Results indicate the presence of a novel distinct arginine transporter in Leishmania promastigotes.
在限定培养基中体外培养的杜氏利什曼原虫前鞭毛体中，对L-精氨酸的转运特性进行了研究。前鞭毛体对精氨酸的摄取呈现出时间依赖性、温度敏感性、pH依赖性和饱和性。代谢抑制剂导致81%-92%的抑制率，表明前鞭毛体中精氨酸的内流是一个需要能量的过程。Na⁺离子的存在对充分发挥活性是必需的。缬氨霉素、短杆菌肽和氨氯吡咪也引起了相当程度的抑制。该转运体似乎在活性位点涉及一个-SH基团。利什曼原虫转运体最显著的特征是赖氨酸和鸟氨酸与精氨酸转运没有明显的竞争。其他中性和酸性氨基酸以及多胺也无效。精氨酸类似物，即硝基-L-精氨酸甲酯、N-硝基-L-精氨酸、氨基胍、胍丁胺和D-精氨酸不被该转运体识别，而N-甲基-L-精氨酸乙酸盐和磷酸-L-精氨酸表现出竞争，表明该转运体具有立体特异性，并且能识别胍基以及精氨酸侧链。在前鞭毛体与细胞外培养基中2或5 mM精氨酸孵育期间，未观察到细胞内摄取的[¹⁴C]精氨酸的交换。摄取的精氨酸中有80%保留在三氯乙酸可溶部分。喷他脒对精氨酸转运产生竞争性抑制，IC50值为40 μM。结果表明杜氏利什曼原虫前鞭毛体中存在一种新型独特的精氨酸转运体。
