Figure 1. Formation of (A) dimers and (B) peroxides from tyrosine, tyramine, N-acetyltyrosine (NAT) and p-hydroxyphenylacetic acid (pOH-PA).

Substrates were incubated with horseradish peroxidase, acetaldehyde and xanthine oxidase, as described in the Experimental section, without (▪) or with (□) SOD. The total amount of hydrogen peroxide generated was 54 μM. Dimers were determined by fluorescence and peroxides by the FOX assay. In the FOX assay, zero-time blanks (typically equivalent to approx. 0.2 μM hydrogen peroxide) have been subtracted. Results are means and S.D. for triplicate analyses from one experiment. Similar results were obtained in two other independent experiments.