Purification and characterization of an intracellular esterase from a Fusarium species capable of degrading dimethyl terephthalate

Abstract

Esterase is the key enzyme involved in microbial degradation of phthalate esters (PAEs). In this study, an intracellular esterase was purified from a coastal sediment fungus Fusarium sp. DMT-5-3 capable of utilizing dimethyl terephthalate (DMT) as a substrate. The purified enzyme is a polymeric protein consisting of two identical subunits with a molecular mass of about 84kDa. The enzyme showed a maximum esterase activity at 50°C and was stable below 30°C. The optimal pH was 8.0 and the enzyme was stable between pH 6.0 and 10.0. The esterase activity was inhibited by Cr3+, Hg2+, Cu2+, Zn2+, Ni2+, and Cd2+. Substrate specificity analysis showed that the enzyme was specific to DMT hydrolysis, but had no effect on other isomers of dimethyl phthalate esters (DMPEs) or monomethyl phthalate esters (MMPEs). These findings suggest that the phthalate esterase produced by Fusarium sp. DMT-5-3 is inducible and distinctive esterases involved in hydrolysis of the two carboxylic ester linkages of DMPEs.