To determine the regio-and enantioselectivity of HheC and HheG mutants in epoxide ring opening of epichlorohydrin (1), cyclohexene oxide (2) and styrene oxide (3) in comparison to respective wild-type enzymes, reactions of 1 mL volume were performed in 50 mM Tris•SO4, pH 7.0 containing 10 mM epoxide, 20 mM azide and 10-200 µg purified enzyme. Reactions were incubated at 22 °C (HheG and its mutants) or 30 °C (HheC and its mutants) with shaking at 900 rpm in an Eppendorf ThermoMixer C. Samples were taken after 15 min for epoxide 1, 30 min for epoxide 3 and 2 h for epoxide 2, and extracted with an equal volume of tert-butyl methyl ether containing 0.1% (v/v) n-dodecane as internal standard. Organic phases were dried over MgSO4 and samples were analyzed by achiral and chiral GC (see Table for details regarding temperature programs and retention times).