Yang C C, Chang L S
Institute of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan, Republic of China.
Int J Biol Macromol. 1989 Feb;11(1):13-6. doi: 10.1016/0141-8130(89)90032-9.
Tryptophan (Trp) fluorescence of two phospholipases A2 (PLA2) from Naja naja atra and Naja nigricollis snake venoms was quenched by acrylamide and iodide. Trp residues in N. naja atra PLA2 were equally accessible to acrylamide and iodide. Iodide quenching studies indicate that there are two classes of Trp fluorophores in N. nigricollis CMS-9. The accessible class consists of Trp-18 and Trp-19. Removal of the N-terminal octapeptide caused a perturbation of the micro-environment of the Trp residues in the PLA2 enzymes. The presence of a substrate lowers the susceptibility of the Trp residues to iodide quenching in N. naja atra PLA2, suggesting that all three Trp residues are at the substrate binding site, but in N. nigricollis CMS-9 Trp-18 and Trp-19 are related to substrate binding.
眼镜蛇和黑颈眼镜蛇蛇毒中两种磷脂酶A2（PLA2）的色氨酸（Trp）荧光被丙烯酰胺和碘化物淬灭。眼镜蛇PLA2中的Trp残基对丙烯酰胺和碘化物的可及性相同。碘化物淬灭研究表明，黑颈眼镜蛇CMS-9中有两类Trp荧光团。可及的一类由Trp-18和Trp-19组成。去除N端八肽会导致PLA2酶中Trp残基微环境的扰动。底物的存在降低了眼镜蛇PLA2中Trp残基对碘化物淬灭的敏感性，表明所有三个Trp残基都位于底物结合位点，但在黑颈眼镜蛇CMS-9中，Trp-18和Trp-19与底物结合有关。
