Fundamental Issues Related to the Origin of Melatonin and Melatonin Isomers during Evolution: Relation to Their Biological Functions

Abstract

Melatonin and melatonin isomers exist and/or coexist in living organisms including yeasts, bacteria and plants. The levels of melatonin isomers are significantly higher than that of melatonin in some plants and in several fermented products such as in wine and bread. Currently, there are no reports documenting the presence of melatonin isomers in vertebrates. From an evolutionary point of view, it is unlikely that melatonin isomers do not exist in vertebrates. On the other hand, large quantities of the microbial flora exist in the gut of the vertebrates. These microorganisms frequently exchange materials with the host. Melatonin isomers, which are produced by these organisms inevitably enter the host’s system. The origins of melatonin and its isomers can be traced back to photosynthetic bacteria and other primitive unicellular organisms. Since some of these bacteria are believed to be the precursors of mitochondria and chloroplasts these cellular organelles may be the primary sites of melatonin production in animals or in plants, respectively. Phylogenic analysis based on its rate-limiting synthetic enzyme, serotonin N-acetyltransferase (SNAT), indicates its multiple origins during evolution. Therefore, it is likely that melatonin and its isomer are also present in the domain of archaea, which perhaps require these molecules to protect them against hostile environments including extremely high or low temperature. Evidence indicates that the initial and primary function of melatonin and its isomers was to serve as the first-line of defence against oxidative stress and all other functions were acquired during evolution either by the process of adoption or by the extension of its antioxidative capacity.

A new balancing act: The many roles of melatonin and serotonin in plant growth and development

“…MEL was discovered in 1958 and the structure elucidated the same year 15,16 . Likewise, 5HT was discovered and identified in animals in the 1930's 3,6,[15][16][17] . In animals MEL is a hormone produced by the pineal gland, while 5HT is commonly produced throughout the nervous system [18][19][20] , though extra-pineal locations of biosynthesis have now been established [20][21][22][23] .…”

Induction of ecdysteroidogenesis, methyl farnesoate synthesis and expression of ecdysteroid receptor and retinoid X receptor in the hepatopancreas and ovary of the giant mud crab, Scylla serrata by melatonin

“…Hence melatonin is called a chronobiotic molecule or hormone of darkness. Apart from pineal gland, it is also identified in different tissues of vertebrates such as the retina, Harderian gland and gastro-intestinal tract (Tan et al, 2014). The hormone melatonin is well-studied in vertebrates and has activity as an autocoid, a hypnotic, and a biological modifier, and is involved in general homeostasis, neurohumoral balance, thermoregulation, sleep-wake patterns, and reproduction through synergic actions with other hormones and neuropeptides (Cassone et al, 1993;Golombek et al, 1996;Hyde and Underwood, 1995;Reiter, 1991;Rowe and Kennaway, 1996;Stankov et al, 1991;Tan et al, 2003).…”

Melatonin as a stabilizer of mitochondrial function: role in diseases and aging

“…Recently, Tan et al (2014) proposed that ability to synthesize melatonin in eukaryotes could be inherited from prokaryotic cells, particularly from photosynthetic alpha-proteobacteria. As the authors noted, the alphaproteobacteria are a group of bacteria currently accepted as being the precursors of mitochondria and probably the oldest organisms with the capacity to synthesize melatonin.…”