Fig. 3.

IMPCT kinetics. (A) Dependence of rate (μmol·min⁻¹·mg⁻¹) at 80°C for CDP-inositol formation by recombinant IMPCT on CTP concentration with L-I-1-P fixed at 1.0 mM. (B) Dependence of the IMPCT rate on L-I-1-P concentration with the CTP fixed at 1.5 mM. The Mg²⁺ cofactor concentration was 5 mM, and the assay pH was 8.0. Data are shown only up to 1.2 mM substrate because at higher concentrations rates are significantly decreased, suggestive of substrate inhibition. Data were fit with a cooperative model, and n = 3 (the average of best fit data for each substrate). The lower specific activities observed for the IMPCT dependence on L-I-1-P is because these rates were acquired with an older preparation of IMPCT.