FIGURE 2.

Effects of guanine nucleotides on the catalytic activity of IMPDH in vitro. Graphs showing the normalized initial velocity values (V ₀ values in the absence of GTP divided by the respective values in the presence of GTP). The V ₀ values used for the normalization of the data are EcIMPDH 16.6 ± 1.4, PaIMPDH 26.0 ± 0.7, BsIMPDH 14.2 ± 0.7, and StcIMPDH 14.0 ± 0.3 nM s⁻¹ (mean ± std. error). Estimated IC₅₀ values for are 455.3 ± 6.3 μM and 147.4 ± 3.9 μM (mean ± std. error) for EcIMPDH and PaIMPDH, respectively. Similar results were obtained for GDP inhibition (Figure S1). BsIMPDH, Bacillus subtilis IMPDH; EcIMPDH, Escherichia coli IMPDH; IMPDH, IMP dehydrogenase; PaIMPDH, Pseudomonas aeruginosa IMPDH; StcIMPDH, Streptomyces coelicolor IMPDH