Non-homologous isofunctional enzymes

Non-homologous isofunctional enzymes (NISEs) refer to any set of evolutionarily unrelated enzymes that catalyze the same chemical reaction. Enzymes that catalyze the same reaction are sometimes referred to as analogous as opposed to homologous, though it is more appropriate to refer to them as "non-homologous" and "isofunctional", hence the acronym NISE. Such enzymes all serve the same end function but do so in different organisms, having evolved apparently independently without detectable similarity in primary and possibly tertiary structures, making them examples of convergent evolution.