Expression and characterization of Phaseolus vulgaris epoxide hydrolase

Abstract:

[Background] Optically pure epoxides and vicinal diols are versatile chiral building blocks. Compared with chemical synthesis, biotransformation mediated by epoxide hydrolases (EHs), an environmental-friendly way, has become the current research focus. [Objective] A gene encoding EH was cloned from Phaseolus vulgaris and heterologously expressed in Escherichia coli. The catalytic characteristic of recombinant EH towards SO was studied. [Methods] By means of computer-aided analysis of EH primary structure, a hypothetical protein from Phaseolus vulgaris (PvEH4) was predicted to have EH activity. Using P. vulgaris total RNA as templet, the PvEH4-encoding gene, pveh4, was amplified by RT-PCR technique and expressed in E. coli BL21(DE3). To assay catalytic characteristics of PvEH4, asymmetric hydrolysis of styrene oxide (SO) was conducted by E. coli/pveh4 whole cells. [Results] The primary structure analysis showed that PvEH4 has the typical characteristics of conserved α/β fold EH motifs. SDS-PAGE analysis displayed that the apparent molecular weight of PvEH4 was 39.4 kD. The enantioselectivity (E value) of PvEH4 towards SO was 10.1, while regioselectivity coefficient, αS and βR was 99.5% and 82.5%, respectively. As the conversion ratio reached 68.1%, (R)-SO with 99.9% ees and 31.9% yield as well as (R)-PED with 92.3% eep and 65.6% yield were simultaneously obtained. [Conclusion] The excavated PvEH4 not only increases the number of plant EHs, but also provides a good reference for EH modification.