Deformylase involved in photorespiration. Prevents excessive accumulation of 5-formyl tetrahydrofolate (THF), a potent inhibitor of the Gly decarboxylase/Ser hydroxymethyltransferase complex. (6S)-10-formyltetrahydrofolate + H2O = (6S)-5,6,7,8-tetrahydrofolate + formate + H(+) Expressed in leaves, cotyledons, roots, seeds and flowers. No visible phenotype. Puru1 and puru2 double mutant shows a 70-fold increase in Gly levels and accumulates elevated levels of 5- and 10-formyl THF. Embryo development arrests between heart and early bent cotyledon stages, and mature seeds are shriveled, accumulate low amounts of lipids, and fail to germinate. Puru1 and puru2 double mutant is only conditionally lethal and is rescued by growth under nonphotorespiratory conditions. Puru1, puru2 and fold1 triple mutant shows no photorespiratory phenotype. Belongs to the PurU family.