Now, at the end of the reaction, because we always have to regenerate our enzyme, the enzyme is never used or depleted or changed in any reaction. We have to break that bond. And that's exactly why we call this bond a temporary or a transient Covalent bond. Now, in our discussion on irreversible suicide inhibitors, we discussed penicillin. And we said that penicillin is an antibiotic that affects a specific bacterial enzyme found in bacterial cells known as glycopeptide transpeptidase. And when we discussed this molecule, we said that inside the active site of glycopeptide transpeptidase is this catalytic residue, namely this serene molecule.