Catalyzes the conversion of hemimercaptal, formed from methylglyoxal and glutathione, to S-lactoylglutathione (PubMed:20454679, PubMed:9705294, PubMed:23122816). Involved in the regulation of TNF-induced transcriptional activity of NF-kappa-B (PubMed:19199007). Required for normal osteoclastogenesis (By similarity). (R)-S-lactoylglutathione = glutathione + methylglyoxal Binds 1 zinc ion per subunit. In the homodimer, two zinc ions are bound between subunits. Regulated by oxidation of Cys-139 in response to the redox state of the cell. Results in the alternative formation of cystine or glutathione-bound cysteine, the latter modification leading to reduced enzyme activity. Reduction of GLO1 was carried out by incubation with 20 mM betamercaptoethanol prior to kinetic analysis. Secondary metabolite metabolism; methylglyoxal degradation; (R)-lactate from methylglyoxal: step 1/2. Homodimer. Glutathionylation at Cys-139 inhibits enzyme activity. Phosphorylated at Thr-107 in the presence of CaMK2. However, this is a consensus site for phosphorylation by CK2 so phosphorylation may be mediated by CK2 rather than CaMK2. Phosphorylation is induced by TNF and suppresses the TNF-induced transcriptional activity of NF-kappa-B. Exists in a nitric oxide (NO)-modified form. The exact nature of the modification is unknown, but it suppresses the TNF-induced transcriptional activity of NF-kappa-B. Variant Glu-111. The measured range is 2-184. Variant Ala-111. The measured range is 2-184. Exists in three separable isoforms which originate from two alleles in the genome. These correspond to two homodimers and one heterodimer composed of two subunits showing different electrophoretic properties. Belongs to the glyoxalase I family. Extended N-terminus.