A collective term for enzymes that hydrolyse starch and glycogen, widely existing in higher plants and animals and micro-organisms. They are classified according to the pattern of decomposition of the substrate as α-amylase, β-amylase, glucoamylase, de-branching enzymes and so on.

As the primary material for the brewing of seishu, rice, consists largely of starch, amylases are amongst the most important enzymes. Glucoamylase and α-amylase are of particular importance.

α-amylase is necessary to liquefy the solid rice, and also degrades the starch into dextrin and other forms which are receptive to the action of glucoamylase. Glucoamylase primarily uses the reaction products of α-amylase as the substrate for glucose production. Yeast ferments the glucose thus produced as a carbon source, so it can be seen that these amylases have great influence on alcohol production in sake.

Furthermore, as amylase produces oligosaccharides and numerous other sugars, it is responsible for the complex sweet flavour characteristic of sake.