CHEMBL5731357

Inhibition Assay: Protein Kinase C beta 2 (PKCβII) catalyzes the production of ADP from ATP that accompanies the phosphoryl transfer to the PKC Pseudosubstrate peptide (A→S, RFARKGSLRQKNV). This transfer is coupled to the oxidation of β-NADH through the activities of Pyruvate Kinase (PK) and Lactate Dehydrogenase (LDH). β-NADH conversion to NAD+ is monitored by the decrease in absorbance at 340 nm (e=6.22 cm−1 mM−1) using a Molecular Devices SPECTRA max PLUS spectrophotometer.A typical assay was carried out on a 96-well, clear microtiter plate in a Molecular Devices spectrophotometer for 20 minutes at 30° C. in 0.1 mL of assay buffer containing 50 mM HEPES, pH 7.4, 5 nM PKC, 23 units of pyruvate kinase, 33 units of lactate dehydrogenase, 0.15 mM peptide, 0.1 mM ATP, 1 mM DTT, 4 mM PEP, 8 mM MgCl2, 0.3 mM NADH, 60 mM CaCl2, 10 mg/mL PS, 50 ng/mL PMA, 7.5% DMSO and from about 10,000 nM to 0.169 nM compound inhibitor. Stock solutions of 3-sn-phosphatidyl-L-serine (PS) and phorbol-12-myristate-13-acetate (PMA) were sonicated for 30 seconds just prior to addition to assay buffer and assays were initiated by the addition of 100 μM ATP.Steady-state kinetic parameters for the bi-bi kinase reaction were determined at saturating phospho-acceptor peptide substrate concentration (0.15 mM) by fitting initial velocity data to the Michaelis-Menten equation, v=V max [S]/(K M +[S]) where v is the measured initial velocity, Vmax is the maximal enzyme velocity, [S] is the ATP substrate concentration, and KM is the Michealis constant for ATP. Enzyme turnover values (kcat) were calculated according to kcat=Vmax[E], where [E] is the total enzyme concentration. Enzyme inhibition constants (apparent Ki values) were determined by fitting initial velocities at variable inhibitor concentrations to a model for ATP competitive inhibition based on the Morrison equation). Morrison, J. F., Biochim. Biophys Acta 185: 269-286 (1969).