Alpha-amylase, α-amylase

Endo-form enzyme that cleaves the alpha-1,4 glycosidic bond in starch.   Also known as liquefying enzyme, dextrinizing enzyme and 1,4-α-D-glucanhydrolas.

Widely found in filamentous fungi and bacteria as well as higher plants and animals, it randomly cleaves the alpha-1,4 glycosidic bond, but does not break down the alpha-1,6 glycosidic bond.

As degradation proceeds, the viscosity of the starch solution substrate is rapidly reduced, and the colour shown in the iodine test changes from blue to purple to red to brown.

The limit for starch degradation is usually less than fifty percent, and its final products are maltose, dextrin and small quantities of glucose.

In terms of optical activity (determined by optical rotation measurement), the reducing sugars produced are said to be in α-D form, which is why the enzyme is called α-amylase.

It is measured by colour changes using the iodine test, that is to say, time-course analysis of purple light absorbance by colorimetry.

The activity of α-amylase koji used in making seishu is usually 1,000-2,000g in Wohlgemuth units, but about 400-800g in the case of ginjo-koji.