Thiolesterase that catalyzes the hydrolysis of S-D-lactoyl-glutathione to form glutathione and D-lactic acid. an S-(2-hydroxyacyl)glutathione + H2O = a 2-hydroxy carboxylate + glutathione + H(+) Binds 1 Fe(2+) or Fe(3+) and 1 Zn(2+) ion per subunit, catalysis is optimal with 1 Fe and 1 Zn. Electron spin resonance indicates the presence of a mixture of protein molecules that contain either Fe(2+) or Fe(3+) and Zn(2+). Mn(2+) is not a cofactor (PubMed:19834746). Secondary metabolite metabolism; methylglyoxal degradation; (R)-lactate from methylglyoxal: step 2/2. Homodimer. Mainly expressed in flowers and flower buds. Also detected in roots and leaves. Belongs to the metallo-beta-lactamase superfamily. Glyoxalase II family.