3,4‐Dihydrocoumarin hydrolase with haloperoxidase activity from Acinetobacter calcoaceticus F46

A novel lactonohydrolase, an enzyme that catalyzes the hydrolysis of 3,4‐dihydrocoumarin, was purified 375‐fold to apparent homogeneity, with a 22.7% overall recovery, from Acinetobacter calcoaceticus F46, which was isolated as a fluorene‐assimilating micro‐organism. The molecular mass of the native enzyme, as estimated by high‐performance gel‐permeation chromatography, is 56 kDa, and the subunit molecular mass is 30 kDa. The enzyme specifically hydrolyzes 3,4‐dihydrocoumarin, and the K m and V max for 3,4‐dihydrocoumarin are 0.806 m m and 4760 U·mg −1 , respectively. The N‐terminal and internal amino acid sequences of the enzyme show high similarity to those of bacterial non‐heme haloperoxidases. The enzyme exhibits brominating activity with monochlorodimedon in the presence of H 2 O 2 and 3,4‐dihydrocoumarin or an organic acid, such as acetate and n ‐butyrate.