A comparative study of the interactions of the nonpolar fluorescent ligand, 1-anilino-8-naphthalene sulfonic acid, with butyryl and acetylcholinesterase

The binding of 1-anilino-8-naphthalene sulfonic acid (ANS) to both horse serum butyrylcholinesterase and eel acetylcholinesterase is accompanied by a marked increase in the fluorescence quantum yield of the dye and is associated with a 30-mμ shift in the fluorescent emission of the fluorochrome toward the blue region of the spectrum. Acetylcholinesterase appears to have three binding sites for the dye while butyryl-cholinesterase has two. ANS inhibits the catalytic activity of both enzymes in an “uncompetitive” manner. The interaction of the dye with acetylcholinesterase brings about an irreversible inactivation of the enzyme. Binding constants, classical kinetic constants, and kinetic constants relating to inactivation have been calculated.