BOVINE INOSITOL MONOPHOSPHATASE - THE IDENTIFICATION OF A HISTIDINE RESIDUE REACTIVE TO DIETHYLPYROCARBONATE

The inositol monophosphatase from bovine brain is inactivated by the h istidine-specific reagent diethylpyrocarbonate. Using 4 mM reagent at pH 6.5, the reaction results in the modification of 3 equivalents of h istidine per polypeptide chain. The loss of activity occurs at the sam e rate as the slowest reacting of these residues. Site directed mutage nesis studies have been used to generate a mutated enzyme species bear ing a His-217-->GIn replacement and have shown that it is the modifica tion of histidine 217 which results in the inactivation of the enzyme.