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. 2026 Sep 15;17:1961230. doi: 10.3389/fpls.2026.1961230

Figure 3.

Panel A bar graph shows serotonin content in ng per assay at different pH values, peaking at pH seven point five. Panel B bar graph shows serotonin content at various temperatures, peaking at fifty-five degrees Celsius. Panel C is a Michaelis-Menten curve showing enzyme velocity versus 5-HTP concentration, with Km one point eight zero six millimolar and Vmax three point zero eight nine nanomoles per minute per milligram protein, at pH seven point five and fifty-five degrees Celsius.

Enzymatic properties and kinetic characterizations of purified AtAAS. Effect of pH (4.5 - 9) (A) and temperature (30 °C - 75 °C) (B) on the enzymatic activity of AtAAS in catalyzing 5-HTP. Enzymatic activity was measured at various pH and temperatures conditions to determine the optimal reaction parameters in PBS buffer with 0.1 mM PLP for 1 hour. (C) Substrate affinity (Km) and maximum reaction velocity (Vmax) were determined for 5‐HTP using Michaelis-Menten kinetics. The reactions were performed in PBS buffer (pH = 7.5) with 0.1 mM PLP and a series of the concentrations of 5-HTP for 1 hour at 55 °C. Data are shown as mean ± SD, n=3.