Abstract
SUMMARY: The E-caprolactone hydrolases (EC 3.1.1-) induced by growth of Acinetobacter NCIB 9871 and Nocardia globerula CL1 with cyclohexanol were purified to homogeneity. Both enzymes constituted approximately 1% of the soluble protein of the bacteria. Each was formed from two electrophoretically indistinguishable subunits and each had a closely similar Mr value (⋍60000). Both enzymes had high turnover numbers typical of carboxyesterases, broad pH-activity spectra and very restricted substrate specificities. In contrast to other bacterial lactone hydrolases they catalysed irreversible lactone hydrolysis and were not inhibited by thiol-reactive compounds. Their sensitivity to Paraoxon (diethyl p-nitrophenylphosphate) suggested that they, in common with mammalian acetylcholinesterase and carboxyesterases, have a functional catalytic centre serine.