Serum amylase (AMY) belongs to the α -amylase, which hydrolyzes the α-1, 4-glycosidic bond inside the polysaccharide molecule in an irregular manner to form a mixture of oligosaccharide, maltose and glucose. AMY is secreted mainly by the salivary glands and pancreas, but also in small amounts by the proximal duodenum, lung, uterus and mammary gland during lactation.

AMY catalyzes the hydrolysis of α-1, 4-glycosidic bonds in starch molecules to produce glucose, maltose and dextrin, etc. Iodine can combine with unhydrolyzed starch to form complex with characteristic absorption peak at 570nm, whose depth can be calculated as amylase activity unit.