Rajaian H, Symonds H W, Bowmer C J
Department of Pharmacology, University of Leeds, UK.
J Vet Pharmacol Ther. 1997 Dec;20(6):421-6. doi: 10.1046/j.1365-2885.1997.00099.x.
Mammalian albumins have two main structurally selective ligand binding sites. Site I binds drugs such as azapropazone, phenylbutazone and warfarin; whereas benzodiazepines, some dansyl amino acids, such as dansylsarcosine, and short chain fatty acids like octanoic acid interact with site II. However, it is not known if non-mammalian albumins have similar binding loci. In this study, drug binding sites on chicken albumin were investigated using site selective fluorescent probes (warfarin and dansylsarcosine) and p-nitrophenyl acetate (NPA); the hydrolysis of which is selectively inhibited by site II ligands. Azapropazone and phenylbutazone decreased the binding of warfarin and dansylsarcosine to a similar extent. Diazepam and octanoic acid also inhibited binding of the two fluorescent probes in a non-selective manner. However, the fluorescence intensity of the warfarin-chicken albumin complex decreased when the pH was increased from 6.0-9.0; but by contrast, the fluorescence of bound dansylsarcosine remained unchanged. Furthermore, the hydrolysis of NPA was selectively inhibited by dansylsarcosine, diazepam and octanoic acid (ligands selective for site II on mammalian albumins), but not by site I selective ligands such as azapropazone and warfarin. Overall, the results suggest that chicken albumin, like mammalian albumins, has discrete binding sites for warfarin and dansylsarcosine.
哺乳动物白蛋白有两个主要的结构选择性配体结合位点。位点I结合阿扎丙宗、保泰松和华法林等药物；而苯二氮䓬类药物、一些丹磺酰氨基酸（如丹磺酰肌氨酸）以及辛酸等短链脂肪酸与位点II相互作用。然而，尚不清楚非哺乳动物白蛋白是否具有类似的结合位点。在本研究中，使用位点选择性荧光探针（华法林和丹磺酰肌氨酸）和对硝基苯乙酸（NPA）研究了鸡白蛋白上的药物结合位点；NPA的水解受到位点II配体的选择性抑制。阿扎丙宗和保泰松对华法林和丹磺酰肌氨酸结合的降低程度相似。地西泮和辛酸也以非选择性方式抑制这两种荧光探针的结合。然而，当pH从6.0升高到9.0时，华法林 - 鸡白蛋白复合物的荧光强度降低；但相比之下，结合的丹磺酰肌氨酸的荧光保持不变。此外，NPA的水解受到丹磺酰肌氨酸、地西泮和辛酸（哺乳动物白蛋白上位点II的选择性配体）的选择性抑制，但不受阿扎丙宗和华法林等位点I选择性配体的抑制。总体而言，结果表明鸡白蛋白与哺乳动物白蛋白一样，具有华法林和丹磺酰肌氨酸的离散结合位点。
