High Quality Content by WIKIPEDIA articles! Enzyme promiscuity is a property most enzymes possess which is essential for the evolution of new enzymatic functions. Enzymes are remarkably specific catalysts, but often do possess other activities that are very small and are under neutral selection, called promiscuous activities. Despite being ordinarily irrelevant physiologically, under new selective pressures these activities may confer a fitness benefit therefore prompting the evolution of the formerly promiscuous activity to become the new main activity. An example of this is the atrazine chlorohydrolase (atzA encoded) from Pseudomonas sp. ADP which evolved from melamine deaminase (triA encoded), which has very small promiscuous activity towards atrazine, a man-made chemical.