It has been recognized that the rate-limiting function of pyruvate kinase M2 (PKM2) in glycolysis plays an important role in distributing glycolytic intermediates for anabolic and catabolic purposes in cancer cells. removal of upstream intermediates to prevent the obstruction of the pathway. The discussion is usually in accordance with the catalytic capacity of glycolytic enzymes, rules range of enzyme activities, metabolic flux control, and thermodynamics. and but no and strain XL-1 blue (Qiagen). Each clone was confirmed by sequencing by Invitrogen. When the culture achieved an absorbance (600 nm) of 0.7, manifestation was induced by 1 mm isopropyl -d-thiogalactoside (Gibco) for 6 h at room heat. The cells were collected and lysed by a freeze/thaw cycle and sonication. The lysate was exceeded through a nickel-Sepharose column (GE Healthcare); the protein not bound to nickel-Sepharose was washed with washing buffer (0.1 m Tris-HCl, pH 7.8, containing 0.5 m NaCl, and 40 mm imidazole), and PK was eluted by using 250 mm imidazole. The purity of recombinant PKs was decided by SDS-PAGE and Coomassie Blue staining. The kinetic characteristic of the PKs was decided by an LDH-coupled activity assay. Glucose Consumption and Lactate Generation 1 106 cells were seeded into 25-cm2 culture flask (Corning) to allow attachment overnight in a humidified CO2 incubator. The culture media were then replaced with fresh complete RPMI 1640 LY500307 medium plus 6 mm LY500307 glucose. The glucose level was assessed automatically by the HK colorimetric method using an Olympus AU2700 system, and the lactate production was decided by the VITROS Chemistry Product LAC Slides using the VITROS 5.1 FS LY500307 system; the L/G ratio was calculated as lactate generated over glucose consumption. Preparation of Cell Lysate 4T1, Bcap37, HeLa, SGC7901, RKO, HepG2, and SMMC7721 cells cultured in complete RPMI 1640 medium with 6 mm glucose and at 70% confluence were washed twice with ice-cold PBS and lysed with M-PERTM mammalian protein extraction reagent supplemented with HaltTM protease inhibitor mixture (both from Thermo Scientific). The resultant crude cell lysates were used for enzyme activity and determination. Protein concentration was assessed by BCA protein assay kit (Pierce). Western Blot Cells were lysed with M-PERTM mammalian protein extraction reagent supplemented with HaltTM protease inhibitor mixture. Protein concentration was assessed by BCA protein assay kit. After heat denaturation, the protein was applied to a 10C12% SDS-polyacrylamide solution, transferred to a PVDF membrane, and then detected LY500307 by the proper primary and secondary antibodies before visualization by Western Lighting Plus ECL kit (PerkinElmer Life Sciences). The primary antibodies used were as follows: rabbit anti-PKM1 and PKM2 (Cell Signaling Technology); rabbit anti-PKLR (Abcam); rabbit anti-HK2 (Cell Signaling Technology); and mouse anti-lactate dehydrogenase A (LDHA) (Cell Signaling Technology). Measurement of Enzyme Activity at Saturating Substrate Concentration The activities of each of the 11 enzymes were individually assessed according to previously reported methods (13,C23). Briefly, a reaction was initiated by addition of the cell lysate (2C20 g of protein) into the reaction buffer, reactant, and when appropriate the cofactor in a total volume of 1 ml. The amounts of the lysates used and the reaction occasions were carefully tested for each enzyme to maintain the linearity for each reaction. The absorbance at a wavelength of 260 nm (phosphoglycerate mutase and enolase) or 340 nm (HK, PGI, PFK1, aldolase, TPI, GAPDH, PGK, PKM2, and LDH) were monitored at 37 C with a spectrophotometer (DU? Series 700, Beckman IRF5 Coulter, Inc.). To get the linearity of each reaction, we added different amounts of cell lysate into the reaction mixture for different enzyme assays. The reaction mixture for each enzyme measurement was as described below. HK Reaction mixture contained 50 mm Hepes, 5 mm MgCl2, 0.1 m glucose, 0.5 mm ATP, 0.2 mm NADP, 1 unit of glucose-6-phosphate dehydrogenase, and the cell lysate was added into the reaction mixture to a final concentration of 20 g of protein/ml. PGI 50 mm Hepes, 5 mm MgCl2, 2 mm Fru-6-P and cell lysate was added into the reaction LY500307 mixture to a final concentration of 5 g of protein/ml. PFK1 50 mm Hepes, 100 mm KCl, 5 mm MgCl2, 5 mm Na2HPO4, 1 mm NH4Cl, 5 mm Fru-6-P, 1.5 mm ATP, 0.2 mm NADH, 0.1 mm AMP, 1 unit of -glycerophosphate dehydrogenase (-GPDH), 1 unit of TPI, 1 unit of aldolase, and cell lysate was added into the reaction mixture to a final concentration of 20 g of.