Takeuchi H, Kim K H, Liu G J, Yasuda-Kamatani Y, Minakata H, Nomoto K
Department of Physiology, Gifu University School of Medicine, Japan.
Acta Biol Hung. 1992;43(1-4):147-58.
The neuroexcitatory peptide isolated from Achatina ganglia was identical to the synthetic Gly-D-Phe-L-Ala-L-Asp with respect to either the bioassay experiments using the Achatina neurones or the instrumental analysis (1H-NMR, SIMS, CD and HPLC). We termed it achatin-I (yield: 50 micrograms from 30,000 animals). Its stereoisomer, Gly-L-Phe-L-Ala-L-Asp, termed achatin-II, was also isolated from the ganglia (yield: 17 micrograms), but this was ineffective on the Achatina neurones. Of the eight possible stereoisomers, only achatin-I markedly showed excitatory effects on the two Achatina neurones, PON and TAN, and [D-Ala3] achatin-I (Gly-D-Phe-D-Ala-L-Asp) had the slight effects. Among the fourteen neurones tested, seven, including the two mentioned above, were excited by achatin-I, whereas no neurone was inhibited. Achatin-I produced an inward current (Iin) with an increase in the membrane conductance (g) under voltage clamp. ED50 of achatin-I for exciting the neurones were 0.20-1.47 x 10(-5) M, and its Emax were 6.33-5.02 nA. Of the achatin-I analogues examined, only the three, Gly-Gly-D-Phe-L-Ala-L-Asp, D-Phe-L-Ala-L-Asp and Gly-D-Phe-L-Ala-L-Asn, produced Iin, but much smaller than that of achatin-I. The equiactive molar ratios (EMRs) of the four effective related peptides (three analogues and a stereoisomer) vs. achatin-I were: 8-60 for Gly-Gly-D-Phe-L-Ala-L-Asp, 200 - > 250 for D-Phe-L-Ala-L-Asp and > 200 for Gly-D-Phe-L-Ala-L-Asn and Gly-D-Phe-D-Ala-L-Asp. The Iin induced by achatin-I was blocked under the /Na+/0-free state, but unaffected under the [Ca2+]-free (replaced with Co2+), [Cl-]0-free or [K+]-enriched (3.0 x) medium, indicating that the Iin is produced by the gNa increase of neuromembrane. We propose that achatin-I having a D-phenylalanine residue is an excitatory neurotransmitter of the Achatina neurones.
从玛瑙螺神经节中分离出的神经兴奋性肽，在使用玛瑙螺神经元进行的生物测定实验以及仪器分析（1H-NMR、SIMS、CD和HPLC）方面，与合成的甘氨酰-D-苯丙氨酰-L-丙氨酰-L-天冬氨酸相同。我们将其命名为玛瑙螺素-I（产量：从30,000只动物中获得50微克）。它的立体异构体甘氨酰-L-苯丙氨酰-L-丙氨酰-L-天冬氨酸，命名为玛瑙螺素-II，也从神经节中分离出来（产量：17微克），但对玛瑙螺神经元无效。在八种可能的立体异构体中，只有玛瑙螺素-I对两种玛瑙螺神经元，即足神经节神经元（PON）和胸神经节神经元（TAN）有明显的兴奋作用，而[D-丙氨酸3]玛瑙螺素-I（甘氨酰-D-苯丙氨酰-D-丙氨酰-L-天冬氨酸）有轻微作用。在测试的14个神经元中，包括上述两个神经元在内的7个神经元被玛瑙螺素-I兴奋，而没有神经元被抑制。在电压钳制下，玛瑙螺素-I产生内向电流（Iin），同时膜电导（g）增加。玛瑙螺素-I兴奋神经元的半数有效剂量（ED50）为0.20 - 1.47×10^(-5) M，其最大效应（Emax）为6.33 - 5.02 nA。在所检测的玛瑙螺素-I类似物中，只有甘氨酰-甘氨酰-D-苯丙氨酰-L-丙氨酰-L-天冬氨酸、D-苯丙氨酰-L-丙氨酰-L-天冬氨酸和甘氨酰-D-苯丙氨酰-L-丙氨酰-L-天冬酰胺这三种产生了Iin，但比玛瑙螺素-I产生的Iin小得多。四种有效相关肽（三种类似物和一种立体异构体）与玛瑙螺素-I的等效活性摩尔比（EMR）分别为：甘氨酰-甘氨酰-D-苯丙氨酰-L-丙氨酰-L-天冬氨酸为8 - 60，D-苯丙氨酰-L-丙氨酰-L-天冬氨酸为200 - >250，甘氨酰-D-苯丙氨酰-L-丙氨酰-L-天冬酰胺和甘氨酰-D-苯丙氨酰-D-丙氨酰-L-天冬氨酸均>200。玛瑙螺素-I诱导的Iin在无钠（/Na+/0）状态下被阻断，但在无钙（用钴离子替代）、无氯（[Cl-]0）或富钾（3.0倍）培养基中不受影响，这表明Iin是由神经膜的钠电导增加产生的。我们提出，具有D-苯丙氨酸残基的玛瑙螺素-I是玛瑙螺神经元的兴奋性神经递质。
