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. 2017 Jan 10;7:2068. doi: 10.3389/fpls.2016.02068

FIGURE 2.

FIGURE 2

Investigation of melatonin formation in P. fluorescens RG11 using 15N double-labeled L-tryptophan as the precursor. (A) Biotransformation pathway of L-tryptophan to melatonin in animals (red) and plants (green). TPH, tryptophan hydroxylase; AAAD, aromatic amino acid decarboxylase; TDC, tryptophan decarboxylase; T5H, tryptamine 5-hydroxylase; AN-SNAT, animal serotonin N-acetyltransferase; PL-SNAT, plant serotonin N-acetyltransferase; AN-ASMT, animal N-acetylserotonin O-methyltransferase; PL-ASMT, plant N-acetylserotonin O-methyltransferase; CAMT, caffeic acid O-methyltransferase. (B) Chemical structures and chromatograms of six unlabeled standards (40–60 ng mL-1). (C) Chromatograms of 15N-tryptophan, 15N-5-hydroxytryptophan, 15N-serotonin, 15N-N-acetylserotonin, and 15N-melatonin in the P. fluorescens RG1 culture. 15N-tryptophan was converted to 15N-5-hydroxytryptophan, and 15N-tryptamine was not detected. ∗, 15N labeled.