Expression of a Novel Epoxide Hydrolase AuEH1 from Aspergillus usamii and Its Enzymatic Properties

Abstract:

A gene encoding a novel epoxide hydrolase （AuEH1），Aueh1，was amplified from the total RNA of Aspergillus usamii by RT-PCR technique and ligated with pET-28a（+），followed by transforming the recombinant plasmid，pET-28a-Aueh1，into E. coli BL21（DE3），forming an engineering strain E. coli/Aueh1. The recombinant AuEH1 （reAuEH1） was expressed in E. coli by IPTG induction. After the cells were disrupted by sonication，the supernatant was collected and used as the reAuEH1 solution. The analytical results indicated that the activity of reAuEH1 was 8.12 U/mL. The temperature and pH optima of reAuEH1 were 40 ℃ and 6.5，respectively. It was stable at a temperature of 40 ℃ or below，and at a pH range of 5~9. Its activity was not significantly influenced by EDTA and metal ions tested except for Ag+ and Cu2+. Under the conditions of 40 mmol/L potassium phosphate buffer （pH 6.5），20 mmol/L racemic styrene oxide （（R，S）-SO） and 0.8 U/mL reAuEH1，in a final volume of 6 mL，the hydrolytic resolution of （R，S）-SO was conducted at 35 ℃ for 50 min. The chiral product （S）-SO was obtained with a molar yield of 30.8% and an enantiomeric excess （e.e.） value more than 99%.