FIGURE 4.

H₂O₂ requires an SFK to phosphorylate and enhance the catalytic activity of SHIP-1. (A) The left panel shows a representative FACS overlay from one donor showing the effect of H₂O₂ on anti–phospho-SHIP-1 levels in T cells with or without PP2 treatment (1 μM). The right panel shows the mean values ± SEM from four independent donors. (B) Effect of H₂O₂ (1 μM) on the catalytic activity of SHIP-1 protein immunoprecipitated from 1 × 10⁶ SEB-activated T lymphocytes. Catalytic activity was quantified using a malachite green phosphatase assay, and protein concentration was determined by Western blot. Data are mean values ± SEM of three independent experiments. *p < 0.05, **p < 0.01.