Reversible formation of S-d-3-phosphoglyceroyl glutathione contributes to cellular protection from acylation by cyclic 3-phosphoglyceric anhydride

Abstract

A spontaneous cyclization of 1,3-bisphosphoglycerate produces a highly reactive cyclic 3-phosphoglyceric anhydride (cPGA), which damages cellular nucleophiles through indiscriminate acylation. Although evidence suggests that most of the cPGA is inactivated by DJ-1, a highly efficient cPGA hydrolase, alternative routes of cPGA detoxification have not been explored. Here, we use a kinetic approach to show that a thiol group of glutathione (GSH) reacts with cPGA to produce the corresponding thioester S-D-3-phosphoglyceroyl glutathione (pgGS). We found that pgGS is unstable and decomposes back to GSH and cPGA with a half-life of 80 minutes providing DJ-1 with another chance to inactivate cPGA. Apart from spontaneous decomposition, pgGS is efficiently hydrolyzed by Glyoxalase II (GlxII); therefore a significant fraction of cPGA that escapes hydrolysis by DJ-1 is trapped by GSH and subsequently detoxified. Experiments with DJ-1-null cells revealed that depletion of GSH causes a multi-fold increase in the cellular level of N-glyceroyl glutamine, confirming that reversible formation of pgGS in reaction of cPGA with GSH serves as a second line of defense against acylation of biomolecules by cPGA.