CARBOXYLESTERASES WITH DIFFERENT SUBSTRATE SPECIFICITY IN HUMAN BRAIN EXTRACTS

Abstract— Methods for the determination of carboxylesterase activity in soluble as well as in particulate samples with p ‐mtrophenylacetate and ‐butyrate and α‐naphthylacetate and ‐butyrate as substrates are described. Of the carboxylesterase activity of human brain, 8‐20% was present in aqueous extracts. Particle‐bound carboxylesterases could not be solubilized. By DEAE‐cellulose chromatography the carboxylesterases were separated into 6 more or less inhomogeneous fractions. One of these was further resolved into 2 fractions by chromatography on CM‐cellulose. Fractions obtained by ion exchange chromatography were resolved into several fractions by isoelectric focusing. Gel chromatography on Sephadex G‐200 resolved the carboxylesterases of brain extract into two fractions (molecular weights about 60.000 and 300,000). At least 4 different types of carboxylesterases could be distinguished on the basis of different substrate specificity.