We adjusted our kinetic model to predict the evolution of the reaction cycle with the peptide as the catalyst in the reaction cycle. For the kinetic model with pyridine present in the system, we neglected the intermolecular phosphate-group transfer between pyridine and pyridinio-Nphosphonate. We empirically determined the reaction rate constants of the direct fuel hydrolysis and the 3-phosphoisomer hydrolysis. The formation (kpPy) and hydrolysis (k-pPy) of pPy were determined by reacting the fuel with pyridine alone and fitting the data using COPASI (Table ). We fixed those rate constants in the kinetic model and fitted the remaining others.