Guaicol peroxidase (GPX):

Total PX (EC 1.11.1.6) will be determined using guaiacol reaction solution (3 mL) containing 10 mM KH₂PO₄ at pH 7, 10 mM H₂O₂, 20 mM guaiacol, and 0.5 mL crude extract (Maehly and Chance, 1954).