FIGURE 6.
Pyrophosphate inhibits rTbHK2. A, reassembled rTbHK2-rTbHK1(S160A) complex or rTbHK1-rTbHK1(S160A) complex was incubated with risedronate (RSDN; 5 mm) or PPi (5 mm) prior to assaying for HK activity. B, complexes generated with a higher percentage of rTbHK2 have increased sensitivity to PPi. Proteins were reassembled with increasing molar amounts of rTbHK2 (while total protein was kept constant at 500 ng/assay) and then assayed for HK activity in the presence or absence of PPi (5 mm). Reassembly yielded TbHK1/TbHK2 ratios of 6:0, 5:1, 4:2, 3:3, 2:4, and 1:5, with untreated samples having ratios of 1.9, 3.1, 5.3, 6.4, 2.4, and 1.3 mmol/min HK activity, respectively. Results are plotted as the percent of this untreated activity remaining after PPi inhibition.