MODIFICATION OF HISTIDINE IN RAT SKELETAL-MUSCLE AMP-DEAMINASE WITH DIETHYL PYROCARBONATE

Diethyl pyrocarbonate inhibited the activity of AMP-deaminase from rat skeletal muscles with second-order rate constant 580 M(-1)-min(-1) at pH 6.5, 23 degrees C. The loss of activity was accompanied by increas ed absorption at 240 nm. The activity of the enzyme was recovered in t he presence of hydroxylamine. The dependence of the recovery on pH ind icates the presence of a group with pK(a) = 6.9 in the active center o f the enzyme. These features of the inactivation indicate that the cat alytic activity of the AMP-deaminase is inhibited by modification of o ne histidine residue per subunit of the tetrameric enzyme molecule.