GLOSSARY

Salivary amylase (ptyalin) is an enzyme secreted mainly by the parotid gland that begins the chemical digestion of starch in the mouth; it breaks alpha-1,4 glycosidic bonds, converting starch into maltose, maltotriose, and dextrins.

Characteristics

• Optimal pH: about 6.7–7; it is gradually inactivated by stomach acid but remains active inside the bolus for a while (about 30–60 minutes).
• Contribution: about 5–30 percent of starch digestion; most is carried out by pancreatic amylase in the small intestine.
• Cofactor: the chloride ion.

Genetics and Evolution

The number of AMY1 gene copies varies between people (2–15 copies or more); populations with