Melatonin biosynthesis in plants: multiple pathways catalyze tryptophan to melatonin in the cytoplasm or chloroplasts

摘要: Melatonin is an animal hormone as well a signaling molecule in plants. It was first identified plants 1995, and almost all enzymes responsible for melatonin biosynthesis had already been characterized these species. from tryptophan requires four-step reactions. However, six genes, that is, TDC, TPH, T5H, SNAT, ASMT, COMT, have implicated the synthesis of plants, suggesting presence multiple pathways. Two major pathways proposed based on enzyme kinetics: One tryptophan/tryptamine/serotonin/N-acetylserotonin/melatonin pathway, which may occur under normal growth conditions; other tryptophan/tryptamine/serotonin/5-methoxytryptamine/melatonin when produce large amounts serotonin, example, upon senescence. The biosynthetic capacity associated with conversion to serotonin much higher than melatonin, yields low level Many intermediates are produced various subcellular compartments, such cytoplasm, endoplasmic reticulum, chloroplasts, either facilitates or impedes subsequent enzymatic steps. Depending pathways, final sites vary at cytoplasm differentially affect mode action