FIGURE 1.

SidNA3 activity assays. Indicative plots of the accumulation of PP_i, as monitored by absorbance at 360 nm, for SidNA3 activity using the 20 proteogenic amino acids, cis-AMHO, and ornithine (Orn) as substrates. The assay was conducted three times using different concentrations of enzyme and substrate. In each case, cis-AMHO was the only amino acid that was adenylated. Subsequently, duplicate assays were conducted to calculate observed k_cat and K_m values (see text for details). AU, absorbance units.