cDNA cloning and characterization of human glyoxalase I isoforms from HT-1080 cells

We have isolated two kinds of cDNA clones encoding glyoxalase I from a human fibrosarcoma HT-1080 cDNA library. One of them is identical to the glyoxalase I cDNA isolated by us, and the other encodes a protein in which alanine at position 111 of the reported sequence for glyoxalase I is replaced by glutamic acid. When the two cDNAs were co-translated in vitro, three bands representing two homodimers and one heterodimer appeared on native polyacrylamide gel electrophoresis, as observed for glyoxalase I purified from human erythrocytes or derived from a HT-1080 cell lysate. Escherichia coli cells carrying an expression vector of one of the novel glyoxalase I cDNAs showed glyoxalase I activity. These results reveal that two isoforms of human glyoxalase I showing different electrophoretic properties result from a change in one amino acid residue.