The reactivation of phosphorylated chymotrypsin

Chymotrypsin, like most other enzymes with esterase activity, is inactivated by combination with organophosphates (Balls & Jansen, 1952). The inactive phosphorylated enzyme is relatively stable in water but hydroxylamine and picolinohydroxamic acid will restore the activity by nucleo- philic displacement of the enzyme from the phosphoryl residue The only reported kinetic study of this process is by Cunningham (1954) on reactivation with hydroxylamine, but his conclu- sions as to mechanism are open to criticism as, at best, only about 30 % of the original enzymic