Some electrospray mass spectrometric evidence for the existence of covalentO‐acyl enzyme intermediates

Electrospray mass spectrometry has been used to measure the masses of the species present in solutions of three serine proteases (alpha-chymotrypsin, subtilisin Carlsberg and subtilisin BPN') before, during and after completion of the hydrolytic reaction with cinnamoyl imidazole and indole acryloyl imidazole. The masses measured during the reaction demonstrated that covalent O-acyl enzyme intermediates had been formed.