Figure 3.

Inhibition of DJ-1 cysteine protease function by oxidation. (A and C) Protease activity of 50 µm DJ-1 WTΔC (A) or 50 µm DJ-1 WT (C) was measured after pre-incubation with the indicated concentrations of H₂O₂ or 1 mm β-ME or mock-treated (control) at 37°C for 30 min by a real-time fluorescence-based protease assay using the fluorogenic substrate BODIPY FL-casein (10 µg/ml). RFU, relative fluorescence units. (B and D) Protease activity was quantified by measuring the initial velocity of the proteolytic reaction under the indicated conditions and normalized to the protease activity of mock-treated DJ-1 WTΔC (B) or DJ-1 WT (D). Data represents mean ± SEM from three independent experiments. *P < 0.05.