Chang L S, Wen E Y, Chang C C
Department of Biochemistry, Kaohsiung Medical College, Taiwan, ROC.
Biochem Mol Biol Int. 1996 Mar;38(3):617-23.
The binding of the apolar fluorescent dye 8-anilinonaphthalene-1-sulfonate (ANS) to Naja naja atra and Bungarus multicinctus phospholipase A2 (PLA2) as well as the ANS fluorescence enhancement of PLA2-ANS complexes were pH-dependent. However, the pH-dependent curves and the ionizable groups perturbed by the binding of ANS were essentially different for the two PLA2 enzymes. Methylation of His residue or removal of the N-terminal octapeptide made the ANS fluorescence of PLA2-ANS complexes become less sensitive to pH changes. Moreover, the N-terminus-removed derivatives showed the same fluorescence-pH profiles. These results, together with the findings that the His residue and the N-terminal residues might locate around the ANS-binding site, suggested that the His residue and N-terminus of the two PLA2 enzymes may interact electrostatically with the bound ANS, and that ionization of these residues should appreciably affect the ANS fluorescence.
非极性荧光染料8-苯胺基萘-1-磺酸盐（ANS）与眼镜蛇和多环扁尾海蛇磷脂酶A2（PLA2）的结合以及PLA2-ANS复合物的ANS荧光增强都依赖于pH值。然而，这两种PLA2酶的pH依赖曲线以及因ANS结合而受到扰动的可电离基团本质上是不同的。组氨酸残基的甲基化或N端八肽的去除使得PLA2-ANS复合物的ANS荧光对pH变化变得不那么敏感。此外，去除N端的衍生物显示出相同的荧光-pH谱。这些结果，连同组氨酸残基和N端残基可能位于ANS结合位点附近的发现，表明这两种PLA2酶的组氨酸残基和N端可能与结合的ANS发生静电相互作用，并且这些残基的电离应该会显著影响ANS荧光。
