Figure 3. Peroxidase activity of recombinant full-length and spliced human COX-1.

Peroxidase activity was measured spectrophotometrically as the increase in absorbance at 417 nm due to the oxidation of the substrate ABTS. The reaction was started by the addition of 1 μl of a solution of 20 mM H₂O₂ in water to the cuvette containing incubation buffer, microsome preparation, ABTS and haem as described in the Experimental section. Microsomes were prepared from COS-7 cells transiently transfected with cDNAs of full-length (COX-1) and spliced COX-1 (SV), or with vector control (pcDNA3.1). Equal amounts of protein were used in the assays.