Design of active-site-directed fluorescent probes and their reactions with biopolymers

Fluorescent probes which are active‐site‐directed, reversible, competitive inhibitors of serum cholinesterase (ChE) enzymes have been designed and synthesized. Reversible inhibitors of enzyme active sites have a unique importance when they act as fluorescent probes, allowing fluorescence spectroscopic detection of conformation changes and activesite dynamics. 5‐Dimethylamino‐naphthalene‐1‐sulfonamido‐ N , N ‐dimethyl‐ n ‐propyl‐amine and its aliphatic quaternary derivative are fluorescent probes for serum cholinesterase. The quaternary probe forms complexes with acetylcholinesterase (AChE). The dissociation constants K d for the two probes with serum ChE are 6.0 × 10 −7 and 6.5 × 10 −7 M . The inhibition constants K i are 3.1 × 10 −6 and 6.3 × 10 −6 M from the slopes of Lineweaver‐Burk plots. The Michelis constant K m for the enzyme was 8.8 × 10 −4 M .