The α-amylases () (CAS 9014-71-5) (alternative names: 1,4-α--glucan glucanohydrolase; glycogenase) are calcium metalloenzymes.  By acting at random locations along the starch chain, α-amylase breaks down long-chain saccharides, ultimately yielding either maltotriose and maltose from amylose, or maltose, glucose and "limit dextrin" from amylopectin. They belong to glycoside hydrolase family 13 (https://www.cazypedia.org/index.php/Glycoside_Hydrolase_Family_13).
Because it can act anywhere on the substrate, α-amylase tends to be faster-acting than β-amylase.  In animals, it is a major digestive enzyme, and its optimum pH is 6.7–7.0.
In human physiology, both the salivary and pancreatic amylases are α-amylases.
The α-amylase form is also found in plants, fungi (ascomycetes and basidiomycetes) and bacteria (Bacillus).