Purification of Mro APO by FPLC (Mono Q, steps two and five). (A) - Early FPLC separation step on a Mono Q column 10/100 column showing four major heme peaks with veratryl alcohol oxidizing activity (further purification focused on the second peak). (B) - FPLC elution profile of the final purification step of Mro APO performed on a Mono Q 5/50 column. Heme absorption at 420 nm (red line), total protein at 280 nm (blue line), NaCl gradient (dotted line). APO activity was detected by the oxidation of veratryl alcohol at pH 5.5. The insets show the respective SDS-PAGE (left) and isoelectric focusing gels (right). The second lane of the SDS-PAGE gel shows the molecular mass of the partially and fully deglycosylated Mro APO protein at 29 and 27 kDa, respectively.