Inhibition of PFKFB3 (unknown origin) expressed in Escherichia coli assessed as fructose -2,6-bisphosphate level using fructose-6-phosphate as substrate and ATP measured after 10 mins by spectrophotometry
Inhibition of PFKFB4 (unknown origin) expressed in Escherichia coli assessed as ADP level preincubated for 15 mins followed by addition of fructose-6-phosphate as substrate and ATP measured after 40 mins by luciferase assay
Inhibition of PFKFB3/PFKFB4 in human Panc1 cells assessed as fructose -2,6-bisphosphate production preincubated for 1 hr followed by addition of D-glucose measured after 2 hrs by spectrophotometry
Kinase Assay (Method A): The kinase activity of the bi-functional enzyme is readily quantified based on the production of F-2,6-P2 as described by Van Schaftingen et al. (1982) Eur. J. Biochem. 129, 191-5. This sensitive assay is based on the potent activation of pyrophosphate dependent phosphofructokinase-1 (PPi-PFK) from potato tubers by F-2,6-P2. The use of a series of coupled enzymes leads to a consumption of NADH (nicotinamide adenine dinucleotide) that can be followed spectrophotometrically (an updated protocol is available in Van Schaftingen, (1984) Methods of Enzymatic Analysis (Bergmeyer, H. U., ed.), 3rd edn., vol. 6, pp. 335-341, Verlag Chemie, Weinheim). A protocol for measurements in 96-well microtiter plate format is also available (Bruni et al., (1989) Anal. Biochem. 178, 324-6). These assay protocols have been adopted for the measurement of the kinase activity of PFKFB3 with some modifications as described in the protocol below. The assay was run in 96-well microtiter plates.
Kinase Assay (Method B): The kinase activity of the bi-functional enzyme is readily quantified based on the production of ADP and F-2,6-P2 from ATP and F6P. The ADP is detected with a kit, ADP-Glo Kinase Assay(a-e), from Promega. The assay is a luminescent ADP detection assay that measures kinase activity by quantifying the amount of ADP produced during the kinase reaction. The assay is performed in two steps; first, after the kinase reaction, an equal volume of ADP-Glo Reagent is added to terminate the kinase reaction and deplete the remaining ATP. Second, the Kinase Detection Reagent is added to simultaneously convert ADP to ATP and allow the newly synthesized ATP to be measured using a luciferase/luciferine reaction. The light generated is measured using a luminescence counter (1450 MicroBeta TriLux).The assay was performed in white 384-well microtiter plates (OptiPlate, 6007299, PerkinElmer) by consecutive additions of 0.1 uL of a test compound solution.