A strain of Klebsiella sp. BK-58 that produces cis-epoxysuccinate was screened and identified. This novel enzyme hydrolyzes cis-epoxysuccinate to l(+)-tartaric acid and was purified to homogeneity. Its molecular mass was 30.1 kDa determined by MALDI-TOF-MS analysis. It was stable up to 50 A degrees C and from pH 5 to 11 with optima at 50 A degrees C and pH 8.5. The enzyme was metal-independent and was strongly inhibited by 1 mM Cu2+ and Ag+, and 1 % (w/v) SDS. The K (m) , V (max) and turnover number (k (cat) ) values for cis-epoxysuccinate were 19.3, 2.24 mM min(-1) and 220 s(-1), respectively.