Human salivary [alpha]-amylase is used in this experimental approach to introduce biology high school students to the concept of enzyme activity in a dynamic way. Through a series of five easy, rapid, and inexpensive laboratory experiments students learn what the activity of an enzyme consists of: first in a qualitative then in a semi-quantitative way. They also learn how some environmental effectors can influence it. The choice of a "human body" enzyme and not an anonymous commercial enzyme is a very attractive one for students. This laboratory approach will be integrated with theoretical knowledge about [alpha]-amylase, starch, their physiological meaning, and biotechnological applications.