Untersuchungen zum Stoffwechsel von Tropan-Alkaloiden, VII. Versuche zur Charakterisierung der Tropacocainesterase

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Abstract
The enzymatic hydrolysis of tropacocaine (benzoyl-pseudotropine) by a preparation of horse serum was studied and compared with that of benzoylcholine and acetylcholine. The enzyme(s) that hydrolyse(s) tropacocaine is (are) very sensitive to physostigmine; this suggests that it is a carboxylesterase, and very similar to the acylcholine acylhydrolases. The optimum pH for the hydrolysis of tropacocaine is 7.2, and for benzoylcholine and acetylcholin, 8.4. The inhibition of the hydrolysis of tropacocaine by neutral salts and by certain other inhibitors also differs from that of benzoylcholine and acetylcholine. So far it has not been possible to separate (or to increase the relative amount of) the tropacocainesterase activity from benzoylcholinesterase activity. Unlike the tropinesterase of rabbit serum, the tropacocainesterase, which is widely distributed in the animal kingdom, only attacks cis-tropine esters; some examples of this are reported. It is proposed that the specific tropacocainesterase reported by Glick and Glaubach does not exist, and that tropacocaine is hydrolyzed by one or more of the unspecific serum cholinesterases, that were isolated from human serum by Pilz.