[PQQ precursor protein] + S-adenosyl-L-methionine = E-Y cross-linked-[PQQ precursor protein] + 5'-deoxyadenosine + L-methionine + H(+)
[pqq precursor protein] + s-adenosyl-l-methionine = e-y cross-linked-[pqq precursor protein] + 5'-deoxyadenosine + l-methionine + h(+)