Evidence for enzymatic action?
When performing an enzyme assay (for amylase), what evidence do you have that an enzyme is involved? Couldn't the disappearance of the starch be caused by some non-enzymatic factor which complexes with the starch and prevents it from reacting with the iodine?
Presumably you have a control reaction with all the reaction components except the amylase. If something else were breaking down or complexing with the starch, it should happen in this control. Otherwise it must be the amylase that is breaking down the starch.