A common way for FAD to become covalently bound to its enzyme is by having a proton

Question:

A common way for FAD to become covalently bound to its enzyme is by having a proton removed from the C-8 methyl group and a proton donated to N-1. Then a cysteine or other nucleophilic side chain of the enzyme attacks the methylene carbon at C-8 as a proton is donated to N-5. Describe these events mechanistically.