Graph of salinity's effect on catalase?

I did an experiment on the effect of salt concentration on catalase activity and got a bell curve.
I understand why it reaches its peak at 1% as 0.9% is its optimum concentration, and it decreases at higher concentrations due to denaturation, but why does activity decrease at lower concentrations.?

Also, I tested catalase activity with no salt, and found that the rate of reaction was higher than that at 0.25% salt concentration but lower than that for 1% concentration. How can this be explained?
Does this mean that catalase only works better with salt with the presence of 1% salt concentration?

Thank you, and I'm sorry if I sound confusing!