Relation of amylase to starch and Lycasin metabolism in human dental plaque in vitro.

Acid production activity (APA) in plaque suspensions from glucose, boiled soluble starch and hydrogenated starch hydrolysate (Lycasin) was studied in 11 subjects. Amylase (alpha-1,4-glucan 4-glucanohydrolase, EC 3.2.1.1) activity was measured in plaque and whole saliva samples from the same persons. Lycasin was found to be hydrolyzed by salivary amylase under the formation of di- and oligosaccharides, however, with a lower rate than starch. A high correlation was found between APA from glucose and from soluble starch and between APA from soluble starch and plaque amylase activity. No correlation was found between amylase activity in saliva and APA from soluble starch or between amylase activity in saliva or plaque and APA from Lycasin. APA from Lycasin was about 62% and from soluble starch about 76% of the APA from glucose. 0-25% of the total number of cultivable microorganisms from the plaque produced extracellular starch-degrading enzymes. No correlation was found between number of starch-degrading microorganisms and APA from soluble starch or between these numbers and the plaque amylase activity. By electrophoreses only amylase fractions of human origin were found in whole saliva, plaque supernatants and plaque suspensions, indicating that the microbial amylase activity in the plaque is low compared with that of salivary origin.