FIGURE 4.

Kinetic analysis of enzyme activation and specificity toward ATP and ADP. A and B, specific activity ± S.D. (indicated as error bars) for TgNTPDase variants with 2 mm ATP or 5 mm ADP and optionally with the addition of 3 mm DTT according to a malachite green assay. Reactions were carried out for 10 min at room temperature. Please note the different scale in A and B. C, ITC-based enzyme assay. Titration of TgNTPDase1ΔCC with ADP as substrate. 3 × 5 μl, 2 × 10 μl, and 12 × 20 μl of a 30 mm ADP were added to 0.4 nm TgNTPDase1ΔCC in a magnesium reaction buffer with reequilibration times of 300 to 350 s. D, calculation of turnover rates from the data in C.