There are two isoforms of human amylase:
pancreatic and salivary amylase.

Pancreatic amylase P-amylase.
Pancreatic a-amylase randomly cleaves the a(1-4) glycosidic linkages of amylose to yield dextrin, maltose or maltotriose. It adopts a double displacement mechanism with retention of anomeric configuration. P-amylase refers to the type of amylase made mainly in the pancreas. P-amylase in blood increases when the pancreas is inflamed or damaged.

Salivary amylase S-amylase.
Amylase is found in saliva and breaks starch down into maltose and dextrin. This form of amylase is also called ptyalin. It will break large, insoluble starch molecules into soluble starches (amylodextrin, erythrodextrin, achrodextrin) producing successively smaller starches and ultimately maltose. Ptyalin acts on linear a(1,4) glycosidic linkages, but compound hydrolysis requires an enzyme which acts on branched products. Salivary amylase is inactivated in the stomach by gastric acid. S-amylase refers to the type of amylase made mainly by the salivary glands. S-amylase in blood increases when the salivary gland is inflamed or damaged.