Mitochondria: the birth place, battle ground and the site of melatonin metabolism in cells

Abstract

It was a surprising discovery when mitochondria,
 as the power houses of cells, were also found to synthesize the potent
 mitochondrial targeted antioxidant, melatonin. The melatonin synthetic enzyme serotonin
 N-acetyltransferase (SNAT) was found in matrix and also in the intermembrane space
 of mitochondria. We hypothesize that the melatonin synthesis occurs in the matrix
 due to substrate (N-acetyl co-enzyme A) availability while the intermembrane
 space may serve as the recycling pool of SNAT to regulate the melatonin
 circadian rhythm. Another surprise was that the melatonin membrane receptors,
 including MT1 and MT2, were also present in mitochondria. The protective
 effects of melatonin against neuronal injury induced by brain ischemia/reperfusion
 were proven to be mainly mediated by mitochondrial melatonin receptors rather
 than the cell surface membrane receptors which is contrary to the classical
 principle. In addition, melatonin metabolic enzyme has also been identified in
 the mitochondria. This enzyme can convert melatonin to N-acetylserotonin to
 strengthen the antitumor effects of melatonin. Thus, mitochondria are the
 generator, battle ground and metabolic sites of melatonin. The biological
 significance of the strong association between mitochondria and melatonin
 should be intensively investigated.

Importance of Melatonin in Assisted Reproductive Technology and Ovarian Aging

“…Therefore, it exists in the cytosol as well as in mitochondria and nuclei [27][28][29][30]. Melatonin, through direct scavenging and indirect antioxidant actions, limits oxidative stress in all cells and protects DNA and other components from damages [31,32]. The antioxidative actions of melatonin and its metabolites are extremely vast, including the ability to neutralize superoxide anion (O 2…”

Nano-ZnO-Induced Drought Tolerance Is Associated with Melatonin Synthesis and Metabolism in Maize

“…Melatonin (N-acetyl-5-methoxy-tryptamine) is an effective free radical scavenger and naturally occurring antioxidant in response to abnormal cellular metabolic and abiotic stress [18]. The original sites of melatonin biosynthesis are mitochondria and chloroplasts in higher plants [19][20][21]. Normally, melatonin biosynthesis is based on tryptophan, which is catalyzed by tryptophan decarboxylase (TDC) and tryptamine 5-hydroxylase (T5H) and converted into serotonin.…”

Effects of Light Quality and Phytochrome Form on Melatonin Biosynthesis in Rice

“…Melatonin acts as a potent free radical scavenger and antioxidant in almost all organisms, including animals and plants [1][2][3][4]. Melatonin acts as a hormone in plants, and as a signaling molecule in a wide range of biological activities [5].…”