Inhibition of the plasma cholinesterase variants by pancuronium bromide and some of its analogues

Pancuronium bromide, a 3,17-diacetoxy-5α-androstane, and three of its analogues, the 17-desoxy, the 3,17-dibutyryloxy and the 16-N-monoquatemary ammonium derivatives have been used as inhibitors of the usual and atypical plasma cholinesterase variants. In all cases the usual enzyme is more sensitive to inhibition by the substituted steroids than the dibucaine resistant enzyme. The relative affinities of the bis-quaternary ammonium compounds for either enzyme is in the order dibutyryloxy derivative > 17-desoxy derivative ? pancuronium bromide. The monoquatemary compound has the least affinity of all the inhibitors for the usual enzyme but the greatest affinity for the atypical enzyme. These observations show that the bis-quaternary compounds are very powerful differentiators of the variants. The monoquatemary derivative shows less differential inhibition, but provides additional evidence that the usual and dibucaine resistant variants differ in structure at or near their esteratic active site.