Abstract:Production of melanin has been described in a variety of life forms ranging from bacteria to human. Though melanin is not essential to the growth of organisms, it can help to improve their competitive abilities through confering organisms diverse functions such as resistance to UV radiation and toxic free radicals elimination. Nowadays, research on enzymes essential for the formation of melanin has attracted more attentions because they can metabolize dozens of phenol compounds. It made these enzymes, like tyrosinase, a significant value in biotechnology application. This review summarizes the present knowledge of melanin categories, biosynthetic pathways and physiological functions.