Fig. 3.

The effect of piperine on the ATPase activity of skinned skeletal muscle fibers and purified myosin. Multiple single fibers were incubated in a small aliquot of relaxing solution, without (column “fiber”) or with 100 μM piperine (column “fiber P”), and their ATPase activity was expressed as the turnover rate per myosin head per second (Fig. S5). Piperine increases the ATPase activity of control fibers by 66 ± 10%. Samples were also run in the presence of 40 μM blebbistatin (columns “fiber B” and “fibers B P” with piperine), which inhibits myosin ATPase activity but not the activity of other enzymes in the fiber, and piperine has little effect on these enzymes. Piperine has a small and not significant effect on the ATPase activity of purified myosin (columns “myosin” and “myosin P”). Together these data show that piperine increases fiber ATPase activity by destabilizing the SRX. Errors are SEM (n = 8–12).