Figure 2.

Dianisidine peroxidase activity in extracts of E. scolopes tissues. Squid light organ, mantle, and digestive gland were each homogenized over ice in ground glass tissue homogenizers containing 500 μl of buffer (50 mM sodium phosphate, pH 6.0). The homogenates were centrifuged at 8000 × g for 20 min at 4°C in a Sorvall RC-5B superspeed centrifuge, and the resulting supernatant fluids were kept on ice. For each assay, 17 μl of the supernatant fluid were added to 483 μl of an assay buffer containing 50 mM sodium phosphate, 0.002% H₂O₂, and 5 μM O-dianisidine·HCl (pH 6.0), and the absorbance of the solution was monitored at A₄₆₀ for 1 min. Concentration of soluble protein was determined spectrophotometrically (18). Enzyme activity was expressed as mol O-dianisidine produced·min⁻¹·mg soluble protein⁻¹ as determined from Beer’s Law (ɛ = 11.3 cm²·millimol⁻¹; ref. 19). Activity of commercially available human MPO was measured for comparison. Bars are averages ± standard deviation (n = 18).