Repair of a certain type of oxidative DNA damage leads to the release of
phosphoglycolate, which is an inhibitor of
triose phosphate isomerase and is predicted to indirectly inhibit
phosphoglycerate mutase activity. Thus, we hypothesized that
phosphoglycolate might play a role in a metabolic DNA damage response. Here, we determined how
phosphoglycolate is formed in cells, elucidated its effects on cellular metabolism and tested whether DNA damage repair might release sufficient
phosphoglycolate to provoke metabolic effects.
Phosphoglycolate concentrations were below 5 µM in wild-type U2OS and HCT116 cells and remained unchanged when we inactivated
phosphoglycolate phosphatase (PGP), the
enzyme that is believed to dephosphorylate
phosphoglycolate. Treatment of PGP knockout cell lines with
glycolate caused an up to 500-fold increase in
phosphoglycolate concentrations, which resulted largely from a side activity of
pyruvate kinase. This increase was much higher than in
glycolate-treated wild-type cells and was accompanied by metabolite changes consistent with an inhibition of
phosphoglycerate mutase, most likely due to the removal of the priming phosphorylation of this
enzyme. Surprisingly, we found that
phosphoglycolate also inhibits
succinate dehydrogenase with a Ki value of <10 µM. Thus,
phosphoglycolate can lead to profound metabolic disturbances. In contrast,
phosphoglycolate concentrations were not significantly changed when we treated PGP knockout cells with
Bleomycin or ionizing radiation, which are known to lead to the release of
phosphoglycolate by causing DNA damage. Thus,
phosphoglycolate concentrations due to DNA damage are too low to cause major metabolic changes in HCT116 and U2OS cells.