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(3+) ion per subunit. Electron spin resonance clearly indicates the presence of Fe(3+) (PubMed:16227621). Binds 1 Fe(2+) or Zn(2+) ion per subunit. Electron spin resonance indicates the presence of either Fe(2+) or Zn(2+), while X-ray crystallography shows the presence of Zn(2+). Mn(2+) is not a cofactor (PubMed:16227621). Secondary metabolite metabolism; methylglyoxal degradation; (R)-lactate from methylglyoxal: step 2/2. Monomer. May be due to a competing acceptor splice site. Belongs to the metallo-beta-lactamase superfamily. Glyoxalase II family.