Peptidase M20 family, aminoacylase-I like (AcyI-like; acylase I; N-acyl-L-amino-acid amidohydrolase; EC 3.5.1.14) subfamily. Acylase I is involved in the hydrolysis of N-acylated or N-acetylated amino acids (except L-aspartate) and is considered as a potential target of antimicrobial agents. Porcine AcyI is also shown to deacetylate certain quorum-sensing N-acylhomoserine lactones, while the rat enzyme has been implicated in degradation of chemotactic peptides of commensal bacteria. Prokaryotic arginine synthesis usually involves the transfer of an acetyl group to glutamate by ornithine acetyltransferase in order to form ornithine. However, Escherichia coli acetylornithine deacetylase (acetylornithinase, ArgE) (EC 3.5.1.16) catalyzes the deacylation of N2-acetyl-L-ornithine to yield ornithine and acetate. Phylogenetic evidence suggests that the clustering of the arg genes in one continuous sequence pattern arose in an ancestor common to Enterobacteriaceae and Vibrionaceae, where ornithine acetyltransferase was lost and replaced by a deacylase. Elevated levels of serum aminoacylase-1 autoantibody have been seen in the disease progression of chronic hepatitis B (CHB), making ACY1 autoantibody a valuable serum biomarker for discriminating hepatitis B virus (HBV) related liver cirrhosis from CHB.