Glutathione traps formaldehyde by formation of a bicyclo[4.4.1] undecane adduct

Glutathione forms complex reaction products with formaldehyde, which can be further modified through enzymatic modi. cation. We studied the non-enzymatic reaction between glutathione and formaldehyde and identified a bicyclic complex containing two equivalents of formaldehyde and one glutathione molecule by protein X-ray crystallography ( PDB accession number 2PFG). We have also used H-1, C-13 and 2D NMR spectroscopy to confirm the structure of this unusual adduct. The key feature of this adduct is the involvement of the gamma-glutamyl alpha-amine and the Cys thiol in the formation of the bicyclic ring structure. These findings suggest that the structure of GSH allows for bi-dentate masking of the reactivity of formaldehyde. As this species predominates at near physiological pH values, we suggest this adduct may have biological significance.