Phylogenetic trees of the total Prxs. A Maximum likelihood tree of 260 PRX sequences from cyanobacteria, higher plants, and Metazoa was constructed as described in the Methods. The Le and Gascuel evolutionary mode (LG) was selected assuming an estimated proportion of invariant sites and four gamma-distributed rate categories to account for rate heterogeneity across sites. Reliability of internal branches was assessed using the bootstrapping method (400 bootstrap replicates). PRXs from distinct subfamilies are indicated by different colours.