Amylase alpha 1C (AMY1C)

amylase alpha 1C (AMY1C) is one of the salivary α-amylase genes, which cleave the α-1,4 glycosidic bonds of starch into maltose, maltotriose and limit dextrins. Digestion of starch therefore begins in the mouth rather than the gut, though the enzyme is inactivated by gastric acid and the bulk of the work is completed in the small intestine by pancreatic amylase — a distinct enzyme encoded by the separate AMY2A and AMY2B genes. The salivary and pancreatic genes sit in one cluster on chromosome 1 and are highly similar in sequence, which is the usual source of confusion between them.

The distinctive feature of the salivary locus is copy number. AMY1A, AMY1B and AMY1C vary in copy number between individuals, from roughly two to more than fifteen, and the number correlates with salivary amylase protein levels and with how quickly starch is broken down in the mouth. Populations with historically starch-rich diets carry higher average copy numbers than those relying on fishing or herding, one of the more frequently cited examples of recent dietary selection in the human genome, though claimed associations between copy number and body mass index have proved inconsistent and technically difficult to measure.

Because the enzyme sets the rate at which dietary starch becomes absorbable glucose, it is of interest in type 2 diabetes and postprandial glucose control: inhibiting α-amylase slows the release of glucose after a starch-containing meal, the principle behind the many plant polyphenols reported as amylase inhibitors, whereas acarbose primarily lowers postprandial glucose by inhibiting intestinal α-glucosidases. Salivary amylase activity also serves as a non-invasive marker in stress and autonomic research, since its secretion is under sympathetic control, and is used in diabetes studies as an accessible readout of carbohydrate handling.