Fig. 3 in NtCOMT1 responsible for phytomelatonin biosynthesis confers drought tolerance in Nicotiana tabacum

Fig. 3. Characterization of NtCOMT1 enzymatic activity. (A) Schematic diagram of melatonin biosynthesis mediated by COMT, converting N-acetylserotonin into melatonin. (B) Purification of His × 6-tagged NtCOMT1, M, molecular mass standards; lane 1, total proteins in 20-μL aliquots of bacterial culture with IPTG; lane 2, 20-μL aliquots of supernatant derived from bacterial cell lysate; lane 3, 20-μL aliquots of precipitated cell lysate; lane 4, purified NtCOMT1 protein. (C) The enzymatic activity of NtCOMT1 under different pH and temperature. (D) Kinetic analysis of purified recombinant NtCOMT1. (E) HPLC analysis of in vitro enzyme activity using N-acetylserotonin as the substrate. The retention time of the new peak is the same as the retention time of the melatonin standard (top: melatonin standard, middle: N-acetylserotonin standard, NtCOMT1: the corresponding protein).