Dienelactone hydrolases play a crucial role in chlorocatechol degradation via the modified ortho cleavage pathway. Enzymes induced in 4-fluorobenzoate-utilizing bacteria have been classified into three groups on the basis of their specificity towards cis- and trans-dienelactone. The catalytic triad of the prototype psepu-clcd1 consists of Cys123, His202 and Asp171