Starch is a polysaccharide found in plants. It is mainly found in the potato tubers and cereals like rice, wheat etc.
The enzyme that acts on starch in the mouth is salivary amylase(ptyalin). Salivary amylase is an enzyme secreted by the salivary glands present in the buccal cavity.
This enzyme splits starch into maltose and dextrins.
Final answer:
The enzyme that acts on starch in the mouth is salivary amylase.