NylB′ carboxylesterase, which is 88% homologous to functional 6-aminohexanoate-dimer hydrolase (NylB) from Arthrobacter sp., possesses trace synthetic activity [0.0004 μmolmin− 1mg− 1 (U/mg)] from 6-aminohexanoate (Ahx) to its oligomers in 90% tert-butyl alcohol. The synthetic activity and the ratio of the synthetic activity to the hydrolytic activity were significantly affected by amino acid substitutions at positions 181, 266 and 370. The ...