HPLC analysis was performed on a 1200 Series Agilent LC system with an InfinityLab Poroshell 120 EC-C18, 4.6 mm x 100 mm, 4µm LC Column (Agilent). Substrates and products were eluted over 14 minutes using a gradient of 2-20% acetonitrile in 20 mM NH4OAc pH 4.5 at 0.3 mL min -1 . Peaks were assigned by comparison to chemically synthesized standards and the peak areas were integrated using Agilent OpenLab software.