Five laccase enzyme isoforms were isolated and purified to homogeneity from the cladodes of xerophytic Cereus pterogonus and Opuntia vulgaris plant species. Catalytic activity of all isoforms was enhanced 40 % by 1 mM Cu(2+) and 1 mM Mn(2+), whereas the activity was inhibited 100 % by 10 mM Fe(2+).