Shimada I
J Gen Physiol. 1978 Jan;71(1):19-36. doi: 10.1085/jgp.71.1.19.
Seven D-amino acids, including D-valine, D-phenylalanine, D-leucine, D-isoleucine, D-tryptophan, D-methionine, and D-alpha-aminobutyric acid, are markedly less stimulative than the corresponding L-isomers that can stimulate the labellar sugar receptor of the fleshfly. A distinct effect of len;th of the amino acid side chain is clearly observed. Esterification and amidation of the alpha-carboxyl group, as well as substitution by hydroxyl and methyl groups, result in extremely decreased responses. Amino acids whose amino groups are located at a position other than the alpha are almost ineffective. With all these rigid stereospecificities of the sugar receptor for amino acids, certain replacement of the alpha-amino group with the hydroxyl or carbonyl group shows a slight increase of the response at neutral pH. Furthermore, certain fatty acids can stimulate the sugar receptor once the solutions are buffered at neutral pH. This observation was further supported by the presence of a remarkable similarity of stimulating effectiveness between amino acids that can stimulate the sugar receptor and those fatty acids. The similarity was shown by testing the response concentration relationships, the stimulating effect of fatty acid derivatives, the effect of treatment with p-chloromercuribenzoate, the behavioral response, and so on.
七种D-氨基酸，包括D-缬氨酸、D-苯丙氨酸、D-亮氨酸、D-异亮氨酸、D-色氨酸、D-甲硫氨酸和D-α-氨基丁酸，其刺激作用明显低于相应的L-异构体，后者能够刺激麻蝇的唇瓣糖受体。氨基酸侧链长度的明显影响清晰可见。α-羧基的酯化和酰胺化，以及羟基和甲基的取代，都会导致反应极度降低。氨基位于α位以外位置的氨基酸几乎没有作用。鉴于糖受体对氨基酸具有所有这些严格的立体特异性，在中性pH值下，用羟基或羰基对α-氨基进行特定取代会使反应略有增加。此外，一旦溶液在中性pH值下缓冲，某些脂肪酸就能刺激糖受体。氨基酸与那些脂肪酸在刺激效果上存在显著相似性，这一观察结果得到了进一步支持。通过测试反应浓度关系、脂肪酸衍生物的刺激作用、对氯汞苯甲酸处理的效果、行为反应等，显示出了这种相似性。
