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Origins of Timezyme: Evolutionary tree showing development of AANAT enzyme. At base of tree is a vertebrate ancestor, labeled as having non-vertebrate AANAT. This form detoxifies potentially hazardous substances. Two lines trace the evolution of non-vertebrate AANAT, which follows one branch, and vertebrate AANAT, which splits off into another set of branches. Along the trunk, labels identify where the AANAT gene duplicates, about 500 million years ago, and then where vertebrate evolution takes place. Silhouettes of elephant shark and ratfish, animals that are representative of early vertebrates, indicate that researchers found both non-vertebrate and vertebrate forms of AANAT in these animals. Further up the trunk, catshark and sea lamprey silhouettes are labeled as having only the vertebrate form of the enzyme. This vertebrate form, also called the timezyme, is found in the brain’s pineal gland and is essential for producing melatonin, which regulates the body’s internal clock.

After analyzing DNA from sea creatures thought to resemble early vertebrates, researchers have pieced together a theory of pertaining to the origin of melatonin, which regulates the body’s 24 hour daily rythms. The AANAT enzyme, or timezyme, is essential for producing melatonin. One form of AANAT is found only in non-vertebrates, and appears to detoxify potentially hazardous compounds. The researchers contend that a second copy of the gene for producing AANAT appeared about 500 million years ago, when the original gene was duplicated. As vertebrate animals evolved, the second copy of the AANAT gene evolved, eventually specializing in producing melatonin. The theory also holds that the original copy of the AANAT gene later disappeared, and its function was taken over by other genes. In support of their theory, the researchers discovered that two animals thought to be like early vertebrates, the elephant shark and the ratfish, produce both the non-vertebrate and vertebrate forms of AANAT. Two other animals thought to have originated later in vertebrate evolution, the catshark and the sea lamprey, had only the vertebrate AANAT gene.
Last Reviewed: 12/20/2013
Vision National Institutes of Health Home BOND National Institues of Health Home Home Storz Lab: Section on Environmental Gene Regulation Home Machner Lab: Unit on Microbial Pathogenesis Home Division of Intramural Population Health Research Home Bonifacino Lab: Section on Intracellular Protein Trafficking Home Lilly Lab: Section on Gamete Development Home Lippincott-Schwartz Lab: Section on Organelle Biology