Functional Analyses and Application of Microbial Lactonohydrolases

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Microbial lactonohydrolases (intramolecular ester bond-hydrolyzing enzymes) with unique properties were found and characterized. The lactonohydrolase from Fusarium oxysporum catalyzes enantioselective hydrolysis of aldonate lactones and D-pantoyl lactone (D-PL). This enzyme is useful for the large-scale optical resolution of racemic PL.. The gene encoding latonohydrolase of F. oxysporum could be overexpressed in Aspergillus oryzae.The Agrobacterium tumefaciens enzyme catalyzes, asymmetric hydrolysis of PL, but the stereospecificity is opposite to that of the Fusarium enzyme. This enzyme gene also, could be expressed in E. coli transformant cells.Dihydrocoumarin hydrolase (DCH) from Acinetobacter calcoaceticus is a bifunctional enzyme, which catalyzes not only hydrolysis of aromatic lactones but also bromination of monochlorodirnedon in the presence of H_2O_2 and dihydrocoumarin. DCH also hydrolyzes several linear esters, and is useful for enantioselective hydrolysis of methyl DL-β-acetylthioisobutyrate and regioselective hydrolysis of methyl cetraxate. DCH in vivo detoxified peroxoacids in conjunction with the catalase.