Competitive inhibition by the D-isomer in racemic mixtures used as substrate in kinetic studies: a simple method for data treatment

A set of equations was applied that allows the use of racemic mixtures for the estimation of kinetic parameters in systems where the L-isomer is substrate and the D-isomer a competitive inhibitor, displaying data as double reciprocal plots. A statistical treatment was introduced that renders compatible the output of presently available programs with the specific model requirements, with few additional calculations. An example is shown with beta-trypsin and its inhibition of benzozyl-D-arginine p-nitroanilide (Ki = 1.12 mM, pH 8,0, 37 degrees C).