The effects of the availability of diet on the levels of exoglycosidases in the supragingival plaque of macaque monkeys.

Supragingival plaque from macaque monkeys was assayed for 13 exoglycosidase enzymes, with appropriate p-nitrophenylglycosides and N-acetylneuramin-lactose used as substrates. Protein in each plaque sample was quantitated with a Coomassie Brilliant Blue dye binding assay, and the specific activity of each enzyme was calculated. In monkeys fed a starch-based diet, fasting resulted in significant increases in the levels of alpha-L-fucosidase, beta-N-acetyl-D-glucosaminidase, beta-N-acetyl-D-galactosaminidase, and neuraminidase. Such changes are consistent with the hypothesis that plaque bacteria degrade salivary glycoproteins for their growth and maintenance in both the presence and especially the absence of dietary food. In contrast, fasting monkeys previously fed a sucrose-rich diet showed no significant alterations in the specific activities of those enzymes whose levels were increased in the starch-based diet group. It is considered likely that, under the conditions prevailing when the sucrose-rich diet is fed, the effective and maximal utilization of sucrose by plaque bacteria necessitates the increased mobilization of nitrogen sources, including the amino sugars of glycoproteins.