PPO activity in Acinetobacter crude cell extracts as measured by continuous fluorescence spectroscopy. (A) In vitro PPO assay results are shown for wild-type (•) and ACN1054 (○) extracts, as well as an extract-free control (▾). (B) PPO activity in membrane and soluble fractions of Acinetobacter extracts. Activity levels in the soluble fraction (○), the membrane fraction (▾), an extract-free control (•), and the membrane and soluble fractions together (▵) are shown. Approximately 0.1 mg/ml protein was present in each extract. Proto, protoporphyrin.