Enantiomeric Tartaric Acid Production Using cis-Epoxysuccinate Hydrolase: History and Perspectives

Abstract

Tartaric acid is an important chiral chemical building block with broad industrial and scientific applications. The enantioselective synthesis of l(+)- and d(-)-tartaric acids has been successfully achieved using bacteria presenting cis-epoxysuccinate hydrolase (CESH) activity, while the catalytic mechanisms of CESHs were not elucidated clearly until very recently. As biocatalysts, CESHs are unique epoxide hydrolases because their substrate is a small, mirror-symmetric, highly hydrophilic molecule, and their products show very high enantiomeric purity with nearly 100% enantiomeric excess. In this paper, we review over forty years of the history, process and mechanism studies of CESHs as well as our perspective on the future research and applications of CESH in enantiomeric tartaric acid production.

Keywords: biocatalyst; cis-epoxysuccinate hydrolase; enantioselectivity; enzyme stability; epoxide hydrolase; immobilization; regioselectivity; stereoselectivity; tartaric acid; whole cell catalyst.

Figure 1

Comparison of CESH[D] and FosX: (a) structure of CESH[D]; (b) structure of FosX; (c) the active site of CESH[D]; (d) the active site of FosX. Both proteins are dimeric and colored in green and cyan for each monomer. The metal ions are shown as yellow balls. The products are shown as magenta and red ball and sticks for CESH[D] and FosX, respectively. In (c,d), the three coordinative residues of the metal ion are shown as blue sticks.