Fig. 1.

Identification of SAICAR as a regulator of PKM2. (A) LC-MS total ion current chromatographs of PKM2-copurified metabolites from glucose-rich (top) and glucose-free cells (bottom). A metabolite further characterized (Fig. S1) is noted with an asterisk (*). A549 cells were incubated in fresh DMEM (10% dialyzed FBS) containing either 25 mM or no glucose for 30 min, and used for metabolite extraction as described in SOM. Extracted metabolites were mixed with recombinant human PKM2 for 30 min at 37°C, cooled on ice, and subjected to a gel-filtration chromatography (exclusion limit: 10 kDa) at 4°C. Metabolites that co-purified with PKM2 were subjected to LC-MS analysis [C₁₈, electron-spray ionization (ESI), positive mode]. (B) Structure of SAICAR. (C) Effect of enzymatically synthesized SAICAR (Fig. S2) on PK activities of (●) PKM2 and (○) PKM1. Avg.±s.d. (n=3).