Alpha-amylase

From Wikipedia:

α-Amylase is a protein enzyme which hydrolyses alpha bonds of large, alpha-linked polysaccharides, such as starch and glycogen, yielding glucose and maltose. It is the major form of amylase found in humans and other mammals. It is also present in seeds containing starch as a food reserve, and is secreted by many fungi.

Alpha-amylase is a major enzyme during mashing, and serves to break down starches into more simple sugars which can be further broken down by Beta-amylase.