Figure 2.

Nucleophile specificity of AcsD: Chemical structures of tested nucleophiles with numbers indicating their percentage reactivity relative to L-serine. Nucleophiles which react twice as fast as water (which has 5% of the reactivity of L-serine) are highlighted in grey and are considered to form a citrate derivative. The original activities with standard deviations are shown in Figure S1. MS, MS/MS and HRMS analyses were carried out for underlined nucleophiles. Functional groups are highlighted in similar colors for clarity, 1,3-diaminopropane was shown to be active in another study¹⁹. Mass spectrometric analysis did not resolve which of the amines reacts. The X-ray crystal structure suggests the primary amine is most likely the nucleophile.