A range of cross-linked enzyme aggregates (CLEAs) was prepared from commercially available aminoacylase 1. Results from three test reactions showed that aminoacylase does not possess aminolysis or alcoholysis activity, both previously ascribed to this enzyme. This result was confirmed using aminoacylase purified by chromatographic techniques, which leads us to conclude that the previously observed acylations of esters and amines is due to other enzymes present as impurities in the crude aminoacylase 1. (C) 2003 Wiley Periodicals, Inc.