Analysis of the sequence of a randomly cloned chromosomal DNA fragment (3.2 kb) from Lactococcus lactis revealed the presence of part of an open reading frame, designated tn,amd1, which specifies a protein displaying significant similarity to aminoacylases from various bacteria. The presence of an immobilised copy of an IS982 element immediately upstream of the coding region of amd1 has probably resulted in the displacement of amd1's native promoter. This genetic organisation was shown to be retained in seven other dairy strains, one of which was only slightly different. The amd1 gene was overexpressed in L. lactis NZ9800 under the control of the inducible nisA promoter and the deacetylating capacity of its gene product was measured on a number of substrates. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.