Presence of a histidine at the active site of the neutral endopeptidase-24.11.

Diethylpyrocarbonate treatment of the neutral endopeptidase (EC 3.4.24.11) inhibits both catalytic activity and binding of the inhibitor [3H]-N(R,S)-3-hydroxyaminocarbonyl-2-benzyl-1-oxopropyl]-glycine. The loss of activity can be reversed by hydroxylamine and almost completely prevented by the competitive inhibitor phenylalanyl-leucine suggesting the presence, as in thermolysin, of a histidine residue at the active site. Butanedione treatment also reduces both catalytic activity and [3H] inhibitor binding. Phenylalanyl-leucine completely protects from the butanedione induced loss of activity, providing further evidence for an essential arginine at the active site. In contrast, the tyrosine modifying agent N-acetylimidazole has no apparent effect on enzyme activity.