chloramphenicol acetyltransferase (CAT) transfers acetate to chloramphenicol thereby inactivating the antibiotic. .EstDL136 catalyzed the deacetylation of 1- and 3- acetyl and 1,3-diacetyl derivates counteracting CAT and restoring Chloramphenicol. EstDL136 also acts as a chloramphenicol hydrolase.It cleaves the amide linkage at C2 of chloramphenicol and thereby confers resistance to bacteria
Title: Crystal structure of chloramphenicol-metabolizing enzyme EstDL136 from a metagenome Kim SH, Kang PA, Han K, Lee SW, Rhee S Ref: PLoS ONE, 14:e0210298, 2019 : PubMed
Metagenomes often convey novel biological activities and therefore have gained considerable attention for use in biotechnological applications. Recently, metagenome-derived EstDL136 was found to possess chloramphenicol (Cm)-metabolizing features. Sequence analysis showed EstDL136 to be a member of the hormone-sensitive lipase (HSL) family with an Asp-His-Ser catalytic triad and a notable substrate specificity. In this study, we determined the crystal structures of EstDL136 and in a complex with Cm. Consistent with the high sequence similarity, the structure of EstDL136 is homologous to that of the HSL family. The active site of EstDL136 is a relatively shallow pocket that could accommodate Cm as a substrate as opposed to the long acyl chain substrates typical of the HSL family. Mutational analyses further suggested that several residues in the vicinity of the active site play roles in the Cm-binding of EstDL136. These results provide structural and functional insights into a metagenome-derived EstDL136.