we postulate that a single serum enzyme , with both paraoxonase and arylesterase activity , exists in two different isozymic forms with qualitatively different properties , and that paraoxon is a `` '' discriminating '' '' substrate ( having a polymorphic distribution of activity ) and phenylacetate is a `` '' nondiscriminating '' '' substrate for the two isozymes .
C0014442
enzyme
C0022173
two isoz