As a tyrosinase inhibitor, azelaic acid reduces synthesis of melanin. The key enzyme in melanin synthesis is tyrosinase. It is an inhibitor of grape polyphenol oxidase and mushroom tyrosinase. The production of melanin occurs in melanocytes in a complex process involving the enzyme tyrosinase. The activity of tyrosinase is similar to catechol oxidase, a related class of copper oxidase. Polyphenol oxidases are a family of di-copper metalloenzymes that include tyrosinase and catechol oxidase. Some common genetic causes include mutations in the tyrosinase gene or OCA2 gene. Albinism is often but not always related to the "TYR" gene coding the tyrosinase enzyme. Human tyrosinase is a single membrane-spanning transmembrane protein. Some insecticides are aimed to inhibit tyrosinase. The best-known type of albinism is OCA1A, which impairs tyrosinase production. Loss of melanogenesis function is linked to the gene that encodes tyrosinase. In other mammals, the diagnosis of albinism is based on the impairment of tyrosinase production. Examples of melanoma specific genes are tyrosinase, MLANA, and PMEL. In both cases inactive proenzymes such as hemocyanin, tyrosinase, and catcholoxidase must be activated first.